WO2024259099A2 - Électrodes en composite tridimensionnel nanoporeux à base de carbone et d'oxydes de métal de transition pour électrocatalyse efficace - Google Patents

Électrodes en composite tridimensionnel nanoporeux à base de carbone et d'oxydes de métal de transition pour électrocatalyse efficace Download PDF

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WO2024259099A2
WO2024259099A2 PCT/US2024/033807 US2024033807W WO2024259099A2 WO 2024259099 A2 WO2024259099 A2 WO 2024259099A2 US 2024033807 W US2024033807 W US 2024033807W WO 2024259099 A2 WO2024259099 A2 WO 2024259099A2
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oxide
transition metal
microlattices
lattice structure
strut
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WO2024259099A3 (fr
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William J . SCHEIDELER
Anand P . TIWARI
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Dartmouth College
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Dartmouth College
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
    • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
    • C25B11/052—Electrodes comprising one or more electrocatalytic coatings on a substrate
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
    • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
    • C25B11/055—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material
    • C25B11/057—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material consisting of a single element or compound
    • C25B11/065—Carbon
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
    • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
    • C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
    • C25B11/091—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/02—Hydrogen or oxygen
    • C25B1/04—Hydrogen or oxygen by electrolysis of water
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/02—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form
    • C25B11/03—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form perforated or foraminous
    • C25B11/031—Porous electrodes
    • C25B11/032—Gas diffusion electrodes

Definitions

  • This disclosure relates to electrodes.
  • Alkaline water electrolysis offers a promising pathway for water splitting, presenting significant potential for the development of sustainable electrocatalysts in energy devices.
  • PGM platinum group metal
  • these PGM-free electrocatalysts currently face challenges regarding their catalytic efficiency.
  • transition metal derivatives such as transition metal phosphides, transition metal nitrides, transition metal alloys, and transition metal oxides because of their moderate capacity to adsorb hydrogen, thereby enhancing kinetics.
  • transition metal oxides show promise owing to their robust stability in alkaline environments.
  • due to their low electrical conductivity and poor kinetics there persists a substantial disparity in their water splitting performance when compared to that of PGMs.
  • a goal of this strategy is to provide an inexpensive, scalable, and highly effective electrocatalyst with good activity.
  • Various wet chemical growth techniques enable the deposition nanostructures on 3D frameworks, such as nanoleaflets, nanosticks formed from spheres, and nanowires for efficient water splitting performance.
  • the limited adhesive force between the catalytically active materials and the 3D substrate results in easy detachment from the substrate during prolonged, high-current electrocatalysis. This limitation restricts their effective performance to lower current densities, rendering them inadequate for meeting the demands of industrial water splitting, which commonly operates at higher current densities.
  • the gas bubbles generated during water splitting on these 3D structures can obstruct a significant number of catalytically active sites, leading to an increase in the device resistance and limited mass transfer, impacting the overall efficiency of water splitting.
  • the mesoscale architecture of the electrode can be important to the overall efficiency of new earth- abundant electrocatalysts for large-scale water splitting.
  • the present disclosure provides an electrocatalyst electrode including a strut lattice structure fabricated of a polymer and a composite disposed on the strut lattice structure that includes at least one transition metal oxide.
  • the composite and the strut lattice structure may be 3D and freestanding.
  • the at least one transition metal oxide may include copper oxide, cobalt oxide, nickel oxide, titanium oxide, zinc oxide, manganese oxide, molybdenum oxide, tungsten oxide, iron oxide, or vanadium oxide.
  • the composite may include a mixture of one or more of the at least one transition metal oxide.
  • the composite may define one or more pores having pore sizes from 10 pm to 1 mm.
  • the one or more pores may be vertically aligned to form channels.
  • the one or more pores may be configured to facilitate bubble release.
  • the strut lattice structure may have an octet, body-centered cubic, simple cubic, or Kelvin cell lattice.
  • the composite may be a coating on the strut lattice structure.
  • the composite may be used for alkaline hydrogen evolution reaction (HER) and oxygen evolution reaction (OER).
  • HER alkaline hydrogen evolution reaction
  • OER oxygen evolution reaction
  • the HER may demonstrate an overpotential of 155 mV at a current density of 10 mA/cm2 and a Tafel slope of 134 mV/dec.
  • the OER may demonstrate an overpotential of 1.42 V at a current density of 10 mA/cm2 and a Tafel slope of 55 mV/dec.
  • the present disclosure further provides a method including stereolithography 3D printing a free-standing strut lattice structure with a periodic pore structure, infusing the strut lattice structure with a metal salt by soaking the strut lattice structure in a concentrated solution of the metal salt dissolved in water, and annealing the strut lattice structure at a temperature from 400 °C to 700 °C.
  • the strut lattice structure may be fabricated of a polymer.
  • the strut lattice structure may have an octet, body-centered cubic, simple cubic, or Kelvin cell lattice.
  • one or more pores in the periodic pore structure may have dimensions from 10 pm to 1 mm.
  • a duration of the infusing may be from 24 to 96 hours.
  • the infusing may occur at a temperature from 60 °C to 100 °C.
  • the annealing may be configured to convert the strut lattice structure to a 3D lattice with graphitic or glassy carbon and a metal/metal oxide coating.
  • oxygen stoichiometries and surface morphologies of the strut lattice structure may be modified by changing the temperature and a time of the annealing.
  • the metal/metal oxide coating may include at least one transition metal oxide, wherein the at least one transition metal oxide comprises copper oxide, cobalt oxide, nickel oxide, titanium oxide, zinc oxide, manganese oxide, molybdenum oxide, tungsten oxide, iron oxide, or vanadium oxide.
  • the metal/metal oxide coating may include a mixture of one or more of the at least one transition metal oxide.
  • FIG. l is a chart showing overpotentials versus Tafel slope for an embodiment disclosed herein and for previous composites.
  • FIGS. 2(a)-2(i) display morphological characterization of different 3D-nanoporous composites at 400 °C, wherein 2(a)-2(c) display SEM images of reduced cobalt oxides and carbon composites, 2(d)-2(f) display SEM images of reduced copper oxides and carbon composites, and 2(g)-2(i) display SEM images of reduced nickel oxides and carbon composites.
  • FIGS. 3(a)-3(i) display morphological characterization of different 3D-nanoporous composites at 450 °C, wherein 3(a)-3(c) display SEM images of reduced cobalt oxides and carbon composites, 3(d)-3(f) display SEM images of reduced copper oxides and carbon composites, and 3(g)-3(i) display SEM images of reduced nickel oxides and carbon composites.
  • FIGS. 4(a)-4(i) display morphological characterization of different 3D-nanoporous composites at 700 °C, wherein 4(a)-4(c) display SEM images of reduced cobalt oxides and carbon composites, 4(d)-4(f) display SEM images of reduced copper oxides and carbon composites, and 4(g)-4(i) display SEM images of reduced nickel oxides and carbon composites.
  • FIGS. 5(a)-5(c) shows XRD analysis characterizing crystal structures of all products and an effect of variable thermal annealing step temperatures.
  • FIGS. 6(a)-6(c) display graphical representation of the electrocatalytic performance for OER.
  • 6(a) displays LSV curves of 3D-nanoporous composites synthesized at 700 °C with the scan rate of 10 mV/sec.
  • 6(b) displays Tafel slopes of 3D-nanoporous composites.
  • 6(c) displays Nyquist plot for 3D-nanoporous composites. All electrochemical experiments were performed in 1.0 M KOH.
  • FIGS. 7(a)-7(c) display graphical representation of electrocatalytic performance for HER.
  • 7(a) displays LSV curves of 3D-nanoporous composites synthesized at 450 °C with the scan rate of 10 mV/sec.
  • 7(b) displays LSV curves of 3D-nanoporous composites synthesized at 400 °C with the scan rate of 10 mV/sec.
  • 7(c) displays Nyquist plot for 3D-nanoporous composites at 150 mV. All electrochemical experiments were performed in 1.0 M KOH.
  • FIGS. 8(a)-8(o) display fabrication and microstructural characterization of the present disclosure.
  • 8(a) displays a graphical scheme of the micro stereolithography (SLA) printing.
  • 8(b) displays an SLA-printed large-scale production of 3D electrodes comprised of microlattices.
  • 8(c) displays a schematic of polymer infusion additive manufacturing (PIAM) process, disclosed herein. 3D polymer scaffolds are converted to transition metal and transition metal oxide interfaces on carbon 3D microlattices. The optical images of the PIAM process for microlattices are shown vertically above their respective schematics.
  • PIAM polymer infusion additive manufacturing
  • 8(d)-8(f) display SEM images of Cu/CuOx on carbon and 8(g)-8(i) display SEM images of Co/CoOx on carbon microlattices.
  • 8(j)-8(l) display EDS elemental mapping of Cu/CuOx on carbon and 8(m)-8(o) display EDS elemental mapping of Co/CoOx on carbon microlattices.
  • FIGS. 9(a)-9(f) display graphical representation of phase and chemical characterization of polymer infusion additive manufacturing.
  • FIGS. 10(a)-10(f) display electrocatalytic performance for HER of Cu/CuOx/C and CuOx/C catalysts in 1.0 M KOH solution.
  • 10(a) displays linear sweep voltammetry.
  • 10(b) displays Tafel plots.
  • 10(c) displays schematic illustration of bubble evolution on powder and 3D microlattices.
  • 10(d) displays calculated turnover frequencies (TOFs) for H2 per active site.
  • 10(e) displays Nyquist plots, derived from electrochemical impedance spectroscopy.
  • 10(f) displays longterm stability (Chronoamperometry) measurement.
  • FIGS. 1 l(a)-l 1(g) display electrocatalytic performance for HER of different microlattices in 1.0 M KOH solution.
  • 11(a) displays a schematics illustration of different types of microlattices.
  • 11(b) displays linear sweep voltammetry.
  • 11(c) displays Tafel plots.
  • 11(d) displays a comparison of overpotential at 10 mA/cm 2 and Tafel slopes between 3D microlattices of Cu/CuOx/C and other 3D structured electrocatalysts.
  • 11(e) displays a schematic illustration of bubble evolution on different microlattices.
  • 11(f) displays ECSA Plots obtained by the extraction of the double-layer capacitance (Cai) from different 3D electrodes.
  • 11(g) displays Nyquist plots, derived from electrochemical impedance spectroscopy.
  • FIGS. 12(a)-12(c) display electrocatalytic performance for OER of Co/CoOx/C and CoOx/C cubic microlattices catalysts in 1.0 M KOH solution.
  • 12(a) displays linear sweep voltammetry.
  • 12(b) displays Tafel plots.
  • 12(c) displays a comparison of overpotential at 10 mA/cm 2 and Tafel slopes between 3D microlattices of Co/CoOx/C and other 3D structured electrocatalysts.
  • FIGS. 13(a)-13(d) display bubble release dynamics.
  • 13(a) displays a schematics illustration of different types of printed 3D microlattices and random foams and respective side view images to show the bubble release with the guide of buoyant force (FB).
  • 13(b) displays high-speed camera images of bubble release from printed 3D microlattices and random foams to evaluate the time for bubble release time.
  • 13(c) displays a schematics illustration of bubble evolution in bare and with microlattices.
  • 13(d) displays the normalized velocity of bubble in different 3D microlattices and random foams.
  • FIG. 14(a) displays a TEM image of Cu/CuOx/C and 14(b) displays a high-resolution transmission electron microscope image of Cu/CuOx/C.
  • FIG. 15(a) displays XPS survey spectra of Cu/CuOx/C and 15(b) displays XPS survey spectra of Co/CoOx/C.
  • FIG. 16 displays thermogravimetric analysis of bare, Cu(NOs)2, and Co(NO )2 soaked microlattices.
  • FIGS. 17(a)-17(c) display cyclic voltammetry of cubic (17(a)), and BCC (17(b)), and Octet 3D microlattices with different scan rates (17(c)).
  • FIG. 18 displays long term stability (Chronopotentiometry) test of cubic Cu/CuOx/C 3D microlattices for HER.
  • FIG. 19 displays Nyquist plots for cubic CoOx/C, and Co/CoOx/C microlattices for
  • FIG. 20 displays enlarged plot of impedance vs time with the details of bubble growth and detachment on powder and 3D microlattices of Co/CoOx/C for OER activity.
  • FIG. 21 displays a long-term stability (chronoamperometry) test of cubic Co/CoOx/C 3D microlattices for OER.
  • FIG. 22 displays water contact angles of (a) 3D microlattices of Cu/CuOx/C, (b) bare 3D microlattices of polymer, (c) carbonized 3D microlattices.
  • FIG. 23(a) displays XRD patterns of bimetallic CuCo/ CuCoOx 3D microlattices
  • FIG. 23(b) displays XRD patterns of bimetallic CoNi/CoNiOx 3D microlattices.
  • FIG. 24 displays STEM images of bimetallic CuCo/CuCoOx, 3D microlattices and respective EDS mapping.
  • FIG. 25 displays SEM images of bimetallic CoNi/CoNiOx 3D microlattices and respective EDS mapping.
  • FIGS. 26(a) and 26(b) display electrocatalytic performance for HER of bimetallic transition metal/metal oxides 3D microlattices in 1.0 M KOH solution.
  • 26(a) displays linear sweep voltammetry.
  • 26(b) displays Nyquist plots.
  • Ranges of values are disclosed herein. The ranges set out a lower limit value and an upper limit value. Unless otherwise stated, the ranges include all values to the magnitude of the smallest value (either lower limit value or upper limit value) and ranges between the values of the stated range.
  • the steps of the method described in the various embodiments and examples disclosed herein are sufficient to carry out the methods of the present invention.
  • the method consists essentially of a combination of the steps of the methods disclosed herein.
  • the method consists of such steps.
  • the embodiments disclosed herein include fabricated continuous 3D free-standing transition metal oxides (e.g., copper oxide (CuO), cobalt oxide (CO3O4), and nickel oxide (NiO)) and carbon composites for efficient alkaline hydrogen evolution reaction (HER) and oxygen evolution reaction (OER).
  • the resulting 3D free-standing transition metal oxide and carbon composite catalyst delivered an efficient electrocatalytic activity for both TIER and OER.
  • chemically- modified reduced copper oxides and carbon composites showed overpotential of 155 mV at a current density of 10 mA/cm 2 and a Tafel slope of 134 mV/dec, which outperformed the other 3D noble metal free oxide electrocatalyst.
  • An advantage of the disclosed embodiments over extruded 3D printed parts based on polymer composites is that the process embodiments disclosed herein allow for greater design freedom and demonstration of catalyst materials with both high porosity and high mechanical durability. Additionally, the disclosed process is freely able to allow for mixing of multiple transition metal precursors to form more complex metal/metal oxide alloys suitable for catalyzing multiple reactions (HER, OER, CO2 reduction, oxygen reduction reaction (ORR), hydrogen oxidation reaction (HOR) etc.).
  • 3D electrodes that include transition metal oxides and carbon are disclosed.
  • the composite can serve as a highly stable and active electrocatalyst for multiple catalytic functions in efficient renewable energy systems.
  • the disclosed 3D-printed lattice-based mesoporous electrodes offer a high-density of electrochemically active sites, facilitate transport of reactants to improve kinetics of efficient electrocatalytic activity, and enhance stability via effective bubble evolution in large-scale electrochemical reactors.
  • Embodiments disclosed herein can be used to prepare and optimize 3D structures and are templates for conformally coating transition metal oxides. Improvements to electrochemical performance can be achieved by performing both the hydrogen evolution reaction and the oxygen evolution reaction using the 3D electrode architecture.
  • the precursor materials e.g., metal salts like metal nitrates
  • the precursor materials are lower cost than other metal catalyst materials, like platinum or IrCh.
  • Other metal oxides are possible, so the electrode design and fabrication disclosed herein can be extended to multiple material systems.
  • a 3D lattice electrode can be fabricated using stereolithography 3D printing.
  • the stereolithography 3D printing can form a free-standing strut lattice structure with periodic pore structures. Examples of this include octet, body-centered cubic, simple cubic, and Kelvin cell lattices, though other designs are possible.
  • Embodiments of the present disclosure include a functional electrocatlyst electrode that may be structural in nature, which render the strut lattice as free-standing. This can use a binder- free approach, such that binder materials or supports are not used in formation. This differs from traditional electrocatalysts that are formed by mounting functional catalyst powders on support structures using binder materials that reduce the effective loading.
  • Embodiments of the present disclosure promote effective mass transport of the electrolyte and gas bubbles at a given operating current density. For example, finer lattices with smaller pores have higher total surface area, which can promote greater activity.
  • dimensions of the pores may be from approximately 10 pm to approximately 1 mm or greater.
  • pore sizes from 50 pm to 1 mm may be used.
  • Other pore sizes may be used.
  • Pores larger than 1 mm may result in a lower performance per weight or per volume because the surface area of the electrocatalyst may be lower due to the coarse or large pore structure.
  • pores up to 10 mm may be used.
  • hierarchical lattices can integrate smaller and larger pores (such as 10 mm). Pores smaller than 10 pm may be used, but may inhibit bubble transport in some applications.
  • various pore sizes and pore dimensions may be used depending on the application.
  • Stereolithography is one 3D printing technology that can be used and that can make a porous lattice structure.
  • the stereolithography process can have high resolution (e.g., down to 50 pm beam sizes).
  • the resulting features can be further shrunk during an annealing process, such as being shrunk down to the 20 pm range.
  • a stereolithography process can be faster than other 3D printing methods, particularly when scaled to high-resolution features.
  • a stereolithography process can be scaled up to the 100’s of cm 2 area that may be relevant to industrialized production of electrolyzers.
  • An infusion step can soak the polymer lattice in a concentrated solution of metal salts dissolved in water.
  • the polymer may be an acrylate-based photopolymer or other material.
  • the metal salts may be hydrated transition metal nitrates or other species.
  • the infusion step may occur over 24-96 hours at a temperature from 60 °C to 100 °C.
  • the metal salt will have soaked into the polymer structure at the end of the infusion step.
  • the concentration of the solution can range from 1 M to 3 M. A concentration that is too low will lead to low catalyst loading and lower performance. Higher concentrations are possible, but may be limited by the metal salt solubility in the solvent.
  • a thermal annealing step is then performed at temperatures from 400 °C to 700 °C to convert the metal oxide/polymer lattice to a 3D lattice with graphitic or glassy carbon and a high- surface area metal/metal oxide coating.
  • the thermal annealing step can induce shrinking, which may enhance the resolution of the 3D printed structures. Isotropic shrinkage in the range of 40-70% in the dimension was observed. For example, for starting structures approximately 4 by 4 mm, the structures were approximately 2 x 2 x 2 mm after the annealing process.
  • the thermal annealing step also can enhance surface area and improve electrochemical performance of the electrodes.
  • X-ray diffraction (XRD) characterization of the 3D structures demonstrates that different crystalline transition metal oxides (e.g., CoOx, CuOx, NiOx) were synthesized on the carbon templates by pyrolizing the metal salt precursor.
  • XRD spectra suggest that different transition metal oxides form with the variation of temperature during thermal annealing.
  • CuOx can be reduced to Cu with increasing temperature.
  • CoOx can be partially reduced with increasing temperature.
  • NiOx is not reduced at higher temperature and possesses only a NiOx phase.
  • transition metal oxides such as TiOx, ZnOx, MnOx, MoOx, WOx, FeOx, VOx, or other species may also be used.
  • transition metal oxides that include iron, titanium, vanadium, manganese, molybdenum, or other materials can be used.
  • Morphological characterization by SEM suggests that different microscale and nanoscale surface morphologies are formed with the variation of temperature during the thermal anneal.
  • CoOx there are three different surface structures formed at different temperatures (400 °C, 450 °C, and 700 °C): planar, textured, and vertical sheets.
  • CuOx there are three different surface structures formed at different temperatures (400 °C, 450 °C, and 700 °C): planar, porous, and microrods.
  • NiOx there are different surface structures formed at different temperatures (400 °C, 450 °C, and 700 °C): planar sheets and flower-like surfaces.
  • the 3D structures with transition metal oxides can be formed with different oxygen stoichiometries and surface morphologies with the modulation of thermal synthesis time and temperature.
  • the synthesis time was approximately 1-3 hours, but this may be extended to produce additional mass loss and crystallization.
  • the synthesis temperature was from 400 °C to 700 °C, but higher temperatures may be used with a vacuum annealing step. For example, a temperature up to approximately 900 °C may be used.
  • Annealing at 400 °C may be needed for adequate carbonization to make the lattice conductive. 400 °C also may be the approximate value to fully decompose the metal nitrate precursor salt to form the metal oxides.
  • 3D transition metal oxides were produced, which may be used as an efficient electrocatalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER).
  • Experimental results show that 3D CoOx may need a lower overpotential (1.39 V) to produce measurable OER activity (10 mA/cm 2 ).
  • This low overpotential for OER is comparable to benchmark noble metal based electrocatalysts.
  • the charge transfer resistance of the resulting 3D structures is low (1.25 Q), which can improve kinetics for OER activity.
  • the 3D CuO x exhibited lower overpotential (66 mV) for HER, which is comparable to other earth-abundant catalysts for HER.
  • the disclosed 3D catalyst electrodes also possess improved performance characteristics and stability compared with powders formed with identical stoichiometries.
  • the oxygen content of the 3D transition metal oxides may be modulated by annealing in either reducing or oxidizing environments.
  • Post-processing also can be used to enhance the activity of the carbon lattice support material.
  • transition metal oxides that include iron, titanium, vanadium, manganese, molybdenum, or other materials can be used. These transition metal oxides can be FeOx, TiOx, V20x, VOx, MnOx, MoOx, etc. Other metals, such as Zn, In, Ir, W, or other species may also be used. These metal oxides may also have improved performance in electrocatalysis.
  • the surface chemistry may be changed through chemical modification processes, including adjusting the time, temperature, and concentration of precursors.
  • Mixture of metal oxides or alloyed metal oxides may be used as catalyst materials.
  • the mixture of the two phases may create lattice strain, leading to a higher density of active sites to enhance electrocatalytic performances.
  • Some examples include CoFeOx, FeNiOx, and CoNiOx, though others are possible.
  • Embodiments disclosed herein may enhance mechanical stability of the electrodes by directly integrating the active catalysis material and the support without additional binders and/or current collector materials.
  • Using a binder can lower the electrocatalytic performance because it displaces active materials and adds an insulating element.
  • binders are not active for electrocatalytic performances and only increase the mass/thickness of the electrodes.
  • the 3D structures disclosed herein are also more mechanically stable that powder electrocatalysts by facilitating bubble evolution.
  • transition metal oxides may be synthesized. This may use other metal salts, such as chlorides, acetylacetonates, acetates, fluorides, bromides, or other materials.
  • composition and structures disclosed herein may be used with other electrochemical devices, such as supercapacitors or fuel cells.
  • Embodiments disclosed herein provide improved stability, intrinsic activity, and active site densities compared to traditional earth-abundant electrocatalysts. This is provided through 3D structuring and chemical modification during heat treatment.
  • the 3D structure may exhibit the smaller overpotential of 1.39 V at 10 mA/cm’ 2 in 1.0 M KOH for OER.
  • 3D printing may enable high-speed additive manufacturing of catalysts in a variety of shapes. These shapes may be used with specific electrolyzer equipment.
  • the 3D printing process involves optimization of support structures located at the vertices of 3D printed lattices to provide support during the printing process.
  • the 3D printed lattice structure may be individualized based on its feature size and its overall porosity so that the micro-lattices formed have favorable mechanical properties.
  • the lattice structure may have pores that are vertically aligned to form channels.
  • the channels may be provided for bubble evolution.
  • the 3D structure may include pores that facilitate bubble release, which avoids blockage of active sites on the catalyst. This may improve performance of the electrode relative to existing designs. For example, cubic lattices form channels that facilitate bubble evolution. Further, octet latices may not have such aligned pores to form a channel, which may cause slower bubble evolution.
  • the electrodes may have overall dimensions from 2 mm to 20 mm.
  • the electrodes may be made into rectangular slabs, discs, or other shapes using 3D printing.
  • This example provides a description of embodiments of a nanoporous 3D transition metal oxide and carbon composite electrodes for efficient electrocatalysis.
  • Water electrolysis serves an environmentally friendly, sustainable and renewable method to produce hydrogen.
  • water electrolysis includes two half-reactions: hydrogen evolution reaction (HER) (4 H + + 4e’ — > 2 H2) on the cathode and oxygen evolution reaction (OER) (4OH- O2 + 2 H2O + 4e‘) on the anode.
  • An acidic medium is generally preferable for HER because a proton rich environment is favorable for hydrogen adsorption on catalyst surface.
  • acidic conditions limit the use of non-platinum group metals as catalysts and causes a stability issue by inducing severe chemical corrosion of electrolyzers.
  • Transition metal oxides such as NiO, CO3O4, CuO, etc. are promising alkaline electrocatalysts for water electrolysis due to their multiple redox states and incompletely filled d orbitals, serving as actives sites for water adsorption and dissociation in alkaline electrolytes.
  • the lack of hydrogen adsorption sites in transition metal oxides restricts the electrocatalytic activity from achieving performance comparable to noble metal-based electrocatalysts.
  • the integration of transition metal oxides with metallic transition metals can provide more hydrogen adsorption sites to achieve enhanced electrocatalytic activity comparable to that of Pt-based electrocatalysts.
  • 3D electrodes with integration of partial oxides of transition metals with active carbon can further enhance the electrocatalytic activity by decreasing the coordination number of transition metals, solving the chemical stability issues of transition metals in alkaline electrolytes as well.
  • mechanical stability of these randomly assembled 3D electrodes can hamper the electrocatalytic activity of these electrodes.
  • continuous 3D mesostructured electrodes may solve the mechanical and chemical stability issues by facilitating fast discharge of evolved gas bubbles and by providing fresh active sites for robust electrocatalytic activity.
  • free standing continuous 3D structured electrodes may be desirable to boost efficient electrocatalytic activity due to its amenability to be mass produced and used directly as an electrode without the need for the addition of binders or current collectors.
  • Embodiments of the present disclosure include a 3D continuous nanoporous freestanding microstructures of transition metal oxides (copper oxide (CuO), cobalt oxide (CO3O4), and nickel oxide (NiO)) and carbon composites for efficient alkaline hydrogen evolution reaction (HER) and oxygen evolution reaction (OER).
  • transition metal oxides copper oxide (CuO), cobalt oxide (CO3O4), and nickel oxide (NiO)
  • HER alkaline hydrogen evolution reaction
  • OER oxygen evolution reaction
  • 3D continuous nanoporous free standing partially reduced CuO and carbon composites showed overpotential of 155 mV at a current density of 10 mA/cm 2 and a Tafel slope of 134 mV/dec, which outperformed other 3D noble metal free oxide electrocatalysts.
  • 3D nanoporous free standing partially reduced CO3O4 showed an overpotential of 1.42 V at a current density of 10 mA/cm 2 and a Tafel slope of 55 mV/dec, surpassing the recently reported cobalt oxide 3D electrocatalysts.
  • the higher electrocatalytic activity of 3D continuous nanoporous free-standing microstructures can be attributed to the carbon composite with partial reduced transition metal oxides, which decreases the coordination number of transition metals by distorting the local structures of transition metal oxides, favoring the hydrogen adsorption.
  • chemically modified reduced copper oxides and carbon composites catalyst also showed superior durability: up to 240 hours of continuous hydrogen evolution without any significant change in overpotential and current density.
  • Carbon protection of the vulnerability to oxidation of partial reduced metallic transition metals enhances the chemical stability and 3D free standing, ordered structures with porosities of a few hundreds of micrometers exposes more active sites, and allows fast discharge of gas bubbles ensures the mechanical stability of the electrode.
  • Continuous 3D-nanoporous composites of partially reduced transition metal oxides and active carbon showed efficient and highly stable electrocatalytic activity for alkaline HER and OER by manipulating the affinity for oxygen and hydrogen species.
  • the use of active carbon also assisted to obtain better ion conductivity and to form the oxide of partially-reduced metallic metals.
  • 3D-nanoporous composites were fabricated by the stereolithography technique followed by an infusion and annealing process with low-cost transition metal salts. To obtain different structures, after infusion of transition metal salts into a photo active polymer, the annealing temperatures was varied from 400 °C to 700 °C.
  • FIGS. 2-4 Representative scanning electron microscopy (SEM) images of the continuous 3D-nanoporous composites fabricated at different temperatures are shown in FIGS. 2-4. It was revealed from SEM images that partially reduced cobalt oxide three different (planar, textured, and vertical sheets) surface structures were formed at different annealing temperatures (400 °C, 450 °C, and 700 °C). However, reduced copper oxide formed planar, porous, and microrods surface morphologies at 400 °C, 450 °C, and 700 °C.
  • nickel oxide formed planar, sheets, and flower like structures at 400 °C, 450 °C, and 700 °C.
  • X-ray diffraction (XRD) analysis was performed (FIGS. 5(a)-5(c)). It was revealed from the XRD patterns that the 3D-nanoporous composites were composed of different oxides such as cobalt oxide, copper oxide, nickel oxide and carbon with peaks one to one corresponding to the standard XRD patterns. It was also revealed from XRD that with the variation of annealing temperature (400 °C to 700 °C), different oxides of transition metals were formed. It was found that with increasing the temperature, the transition metal oxides behave quite differently. In the case of copper oxide, it was mostly reduced to copper by increasing the temperature. However, cobalt oxide was reduced partially at higher annealing temperatures. Moreover, nickel oxide was not reduced at all with increasing the temperature. The broad peak 20° to 30° in all composites revealed the presence of amorphous carbon.
  • annealing temperature 400 °C to 700 °C
  • the HER and OER electrocatalytic activities of the 3D-nanoporous composites of transition metal oxides and carbon were evaluated in 1.0 M KOH electrolyte using a 3-electrode system. All potentials were referenced to the reversible hydrogen electrode (RHE).
  • RHE reversible hydrogen electrode
  • the OER activities of the nanopattems were evaluated by comparing linear sweep voltammetry (LSV) parameters at a scan rate of 10 mV/sec. As shown in FIG. 6(a), the overpotential to obtain a 10 mAcm’ 2 current density of the 3D-nanoporous composites of cobalt oxide electrode was the smallest (1.42 V) when compared with copper oxide (1.49 V), and nickel oxide (1.66 V).
  • the overpotential of the 3D-nanoporous composites of cobalt oxide electrode was close to that of a state- of-the-art noble metal oxides electrocatalyst under the same conditions. It was found that the composites, which are formed at 700 °C, showed good electrocatalytic activity for OER. However, composites formed at 400 °C and 450 °C showed poor electrocatalytic activity for OER. To determine the OER kinetics, the LSV curves were fitted to obtain Tafel plots. Tafel plot analysis provided information about the rate-determining steps. FIG.
  • FIG. 7(a) shows the LSV curves of the 3D-nanoporous composites of transition metal oxides and carbon in 1.0 M KOH electrolyte, measured at scan rate of 10 mV/sec.
  • the 3D-nanoporous composites of copper oxide, synthesized at 450 °C had lowest overpotential 150 mV to obtain of 10 mAcm' 2 current density when compared with cobalt oxide (305 mV), and nickel oxide (350 mV).
  • 3D-nanoporous composites of copper oxide can be attributed to the mixed state of copper oxides and metallic copper due to its multiple redox states (Cu°, Cu Cu +2 and Cu +3 ), which expose many active catalytic sites, ensuring fast exchange of protons for hydrogen adsorption and desorption.
  • 3D-nanoporous composites of cobalt oxide were not reduced at 450 °C to produce a mixed state of cobalt oxides and metallic cobalt (FIG. 5(a)).
  • the mixed states of transition metal oxides and transition metals were used for facile charge transportation and adsorption/desorption of oxygen species.
  • Embodiments of the present disclosure include 3D-nanoporous composites of mixed state of transition metal oxides and carbon as electrocatalysts for water electrolysis in alkaline medium.
  • the morphological feature with the combination of micro and nano pores provides more active sites, boost the reaction kinetics, and enhance the mechanical and chemical stability of electrodes by fast discharge of evolved gas bubbles.
  • mixed state of transition metal oxides and metallic transition metals with carbon interactions enhance electrocatalytic activity.
  • 3D-nanoporous composites of cobalt oxides exhibit superior OER performance in alkaline with overpotential close to noble metal based electrocatalysts.
  • 3D-nanoporous composites of copper oxide exhibit favorable HER activity.
  • Embodiments of the present disclosure include 3D-nanoporous composites electrocatalysts used for the conversion and storage of energy.
  • EXAMPLE 2 [0102] This example provides a description of embodiments of 3D printed microlattices of transition metal/metal oxides for highly stable and efficient water splitting.
  • PIAM polymer infusion additive manufacturing
  • Co/CoOx on carbon (Co/CoOx/C) microlattices display favorable activity with the lowest overpotential (1.40 V to gain 10 mA/cm2) among all reported PGM-free electrodes.
  • This example explores the gas phase mass-transport properties of these 3D microlattices via microscopic imaging of bubble evolution, finding that the outstanding electrocatalytic performance and long-term stability of microlattice electrodes leverages their mesoscale (100-300 pm) pores, providing accessibility of electrolytes, maximizing utilization of active sites, and ensuring rapid evolution of gas bubbles.
  • embodiments of the present disclosure include a technique for manufacturing 3D mesostructured electrocatalysts with deep control of liquid and gas phase mass-transport, enhancing the efficacy of alkaline water electrolysis.
  • This example targeted the application of high-resolution additive manufacturing of a periodic 3D micro/mesostructured electrode to enhance bubble release and expedite the mass transfer of surrounding electrolyte to boost the rate and stability of electrochemical reactions for efficient large-scale water splitting.
  • additive manufacturing including 3D printing, has emerged as a promising method for producing customized structures with precise digital control. So far, 3D microstructured electrocatalysts have been prepared using direct ink writing (DIW), indirect fused deposition modeling (FDM), or selective laser melting (SLM).
  • DIW direct ink writing
  • FDM indirect fused deposition modeling
  • SLM selective laser melting
  • Extrusion-based methods like FDM and DIW offer benefits including affordability, speed, and simplicity, yet they also come with limitations such as restricted design flexibility, lower spatial resolution, weaker mechanical properties, and subpar surface smoothness.
  • Selective Laser Melting (SLM) constitutes an integral element within the power bed fusion (PBF) methodology, widely employed in metal 3D printing due to its capacity for precise output.
  • PPF power bed fusion
  • the present state of manufacturing within this process involves high costs because of the low speed and high cost of feedstocks.
  • photopolymerization based 3D printing of polymers offers an alternative for producing large area high-resolution 3D microstructures at a lower cost.
  • SLA stereolithography
  • This example provides a description of the fabrication and architectural design of 3D free-standing microlattices integrating highly active transition metal/metal oxides via SLA (stereolithography) (shown in FIGS. 8(a) and 8(b)) for efficient electrocatalytic water splitting under alkaline conditions.
  • This method utilizes polymer-based 3D scaffold templates designed explicitly for high gas evolution efficiency to improve electrode stability and enhance water splitting performance. These scaffolds were converted into continuous 3D microlattices of transition metal/metal oxides on carbon by a polymer infusion additive manufacturing (PIAM) method to enhance the efficiency of both the alkaline hydrogen evolution reaction (HER) and oxygen evolution reaction (OER).
  • PIAM polymer infusion additive manufacturing
  • the 3D microlattices composed of copper oxide (CuOx) and copper (Cu) on carbon (Cu/CuOx/C) exhibited high performance (overpotential of 145 mV at 10 mA/cm 2 and a Tafel slope of 134 mV/dec) exceeding that of previously reported Cu-based oxide electrocatalysts.
  • the 3D microlattices including cobalt oxide (CoOx) and cobalt (Co) on carbon (Co/CoOx/C) displayed an overpotential of just 1.40 V at 10 mA/cm 2 , with a Tafel slope of 55 mV/dec.
  • microlattices exhibit superior durability, enduring up to 240 hours of continuous hydrogen and oxygen evolution without significant change in overpotential and current density. This durability is attributed to their ordered microstructures with 100 - 300 pm pores that expose more active sites and allow for fast discharge of bubbles, ensuring mechanical and chemical stability of the electrodes.
  • the efficient and rapid discharge of bubbles from the 3D printed microlattices is influenced by both buoyancy and surface tension, resulting in more effective bubble release compared to flat surfaces due to the ordered pores that provide mesoscale aligned channels favorable for bubble propagation and electrolyte diffusion.
  • PIAM polymer infusion additive manufacturing
  • Stereolithography is employed to create various 3D scaffold templates with adjustable lattice structure, pore size, and volumetric porosity.
  • the 3D scaffold templates were immersed in an aqueous solution of a metal nitrate salt precursor, facilitating its infusion into the polymer, like in a hydrogel additive manufacturing (HIAM) approach.
  • HIAM hydrogel additive manufacturing
  • Calcination in a vacuum converts the metal-salt-infused polymer to coatings consisting of metal oxides on carbon.
  • Subsequent reduction in forming gas (95% N2, 5% H2) yields transition metal and transition metal oxide interfaces on the carbon 3D microlattices.
  • PIAM catalytic 3D microlattices of Cu/CuOx on carbon
  • Co/CoOx on carbon Co/CoOx/C
  • the magnified SEM of Cu/CuOx/C also shows a continuous lamellar structure originating from the layer-by-layer SLA process (FIG. 8(f)), whereas the Co/CoOx/C exhibits a similarly dense structure with micron-sized particles on the surface (FIG. 8(i)).
  • Energy dispersive X-ray spectroscopy (EDS) mapping shows conformal distribution of Cu/CuOx shell on carbon (FIGS. 8(j), 8(k) and 8(1)), and homogenous distribution of Co/CoOx on carbon (FIGS. 8(m), 8(n), and FIG. 8(o)), confirming a well-defined core-shell structure of each individual beam in the 3D microlattices.
  • TEM transmission electron microscopy
  • FIGS. 9(a) and 9(d) show the XRD measurements of calcined 3D CuOx on carbon microlattices derived from PIAM of Cu(NCh)2 and 3D CoO x on carbon microlattices derived from Co(NO3)2, respectively.
  • the CuOx/C and CoOx/C XRD patterns show the presence of only the oxide phases of Cu and Co after calcination.
  • FIGS. 9(b) and 9(c) shows the Cu 2p XPS spectra and fitting curves of CuOx/C, and Cu/CuOx/C.
  • the binding energy of 932.1 eV was distinctive of the Cu 2 O phase within copper oxide, whereas the prevailing binding energy at 940.5 eV signified CuO in the XPS spectra of CuOx/C. After reduction, it was observed that the CuO peak disappeared in Cu/CuOx/C, and the 932.1 eV peak shifted to 932.
  • the calculation of the surface area of microlattices follows a methodology outlined in the methods section of this example. This validated that the 3D microlattices both expose a higher abundance of active sites and decreased interface resistance between the electrolyte and the electrode, thereby boosting electrocatalytic efficiency.
  • the Tafel plots were derived from the polarization curves to delve into the reaction kinetics occurring on each electrode, shown in FIG. 10(b).
  • the Tafel slope of Cu/CuOx/C microlattices was 134 mV/dec’ 1 , which was approximately 4X lower than that of Cu/CuOx/C powder (392 mV/dec’ 1 ), confirming that active materials coupled with appropriate 3D microstructuring facilitated the binding between the catalyst and the adsorbates, enhancing HER kinetics.
  • the improved dynamics observed in 3D microlattices could stem from the effective release of generated gas bubbles, which creates new surface-active sites for adsorbates, as illustrated in FIG. 10(c).
  • Density of Cu/CuOx 6.31 g cm’ 3 .
  • Average size of nanoparticle 30 nm. The shapes of the nanoparticles are approximated to spherical.
  • Loading amount of MXene on the electrode is 1 mg/cm 2 .
  • the TOF value of the 3D microlattices with Cu/CuO x /C is 0.82 s' 1 at an overpotential of 150 mV - 4X higher than that of powdered Cu/CuOx/C (0.21 s' 1 ) and higher than that of reported 3D structured Cu/CuOx.
  • electrochemical impedance spectroscopy (EIS) was used to calculate charge-transfer resistance (Ret), shown in FIG. 10(e).
  • the Ret of the 3D microlattices composed of Cu/CuOx/C was 5X lower (7.0 Q) than that of the powder control (36.2 Q), which matched with the other kinetics and suggested that the formation of gas bubbles obstructs a significant portion of the catalytically active surface area within the powdered sample, leading to heightened ohmic resistance.
  • uninterrupted electrolysis chronoamperometry was conducted in 1 M KOH at a fixed potential of 210 mV versus RHE, maintaining an initial current density of 20 mA/cm 2 . As depicted in FIG.
  • the 3D microlattice exhibited minimal reduction in activity over 120 hours of continual operation, an indication of its stability.
  • the stability of the Cu/CuOx/C powder was inferior, showing large fluctuations even under low current density. These fluctuations could arise as bubbles form on the powder surface, impeding active sites and elevating resistance between these sites and the electrolyte.
  • FIG. 11(a) To characterize the influence of the specific 3D microarchitecture on electrocatalytic activity, various microlattices were printed, including cubic, body-centered cubic, and octet structures, as depicted in FIG. 11(a). The highest electrocatalytic activity was observed in cubic Cu/CuOx/C microlattices, as revealed by LSV (FIG. 11(b)). The superiority of cubic architectures can be attributed to the directional structure of the microlattices, which facilitate the diffusion of electrolytes into the 3D electrodes and efficient bubble release without any obstacles. This, in turn, reduces the resistance between the electrolyte and the electrode while maximizing the utilization of active sites for electrocatalytic activity. Tafel plots from the polarization curves (FIG.
  • the electrochemically active surface area (ECSA) was extracted for the microlattices by conducting cyclic voltammetry (CV) measurements to determine the electrical double-layer capacitance (EDLC) (Cai) (shown in FIGS. 17(a), 17(b), and 17(c)), which is directly proportional to ECSA.
  • EDLC electrical double-layer capacitance
  • FIG. 11(g) displays Nyquist plots, derived from the electrochemical impedance spectroscopy.
  • the Tafel plots were extracted from the polarization curves, as illustrated in FIG. 12(b).
  • the overpotential and Tafel slope of our Co/CoOx/C microlattice catalysts is 1.40 V vs RHE at 10 mA/cm 2 and 51 mV/dec' 1 for OER activity, which is the best among the reported 3D structured and noble metal free electrocatalysts, shown in FIG. 12(c).
  • EIS was measured to extract the charge transfer resistance (Ret) (shown in FIG. 19).
  • N2 gas was supplied at a flow rate of 1 mL/s through a syringe needle into slabs of 3D structured electrodes approximately 4 mm thick, comparable to the catalyst microlattice dimensions.
  • the initial injection of gas produced singleton bubbles that then propagated through the lattice due to the upward buoyant force (FB).
  • This bubble evolution in cubic and BCC lattices was also faster than evolution through random foams (At ⁇ 200 - 400 ms) (shown in FIG. 13(b)), and even lower than that reported for other 3D printed structures.
  • FIG. 13(c) shows a definition of the bubble evolution velocity in pure electrolyte (vo) and the velocity of evolution in porous solids such as microlattices (vi).
  • the normalized bubble velocity in 3D printed cubic microlattices was highest ( ⁇ 0.8) among 3D printed microlattices and random structures, further confirming that 3D printed cubic microlattices are efficient for bubble release for achieving favorable electrocatalytic activity.
  • the hydrophilicity of the Cu/CuOx/C microlattices was characterized, comparing against the carbonized and polymer microlattices.
  • the contact angle between the gas-liquid interface and the lattice surface was determined to be 48.7°, 99.4° and 81.6° for Cu/CuOx/C microlattices, carbonized lattices, and polymer lattices, respectively (shown in FIG. 22).
  • the surface wettability of 3D microlattices composed of Cu/CuOx/C promotes the creation of evenly sized hydrogen bubbles, a factor in rapid bubble release and reduced charge transfer resistance.
  • X-ray diffraction (XRD) analysis was performed. It was revealed from the XRD patterns that the 3D-nanoporous composites are composed of bimetallic oxides such as copper/cobalt oxide, cobalt/nickel oxide, and carbon with peaks one to one corresponding to the standard XRD patterns, as shown in FIGS. 23(a) and 23(b).
  • XRD X-ray diffraction
  • this example measured HER activity of bimetallic transition metal/metal oxides 3D microlattices with single transition metal/metal oxides 3D microlattices control sample of identical composition by linear sweep voltammetry (LSV) curves, shown in FIG. 26(a).
  • Single transition metal/metal oxides 3D microlattices exhibit electrochemical activity for HER, but need a higher overpotential of 350 mV to produce a current density of 10 mA/cm 2 .
  • the bimetallic transition metal/metal oxides 3D microlattices notably enhances the HER activity, achieving a low overpotential of 230 mV at 10 mA/cm 2 .
  • the charge-transfer resistance Ret of the 3D microlattices with bimetallic transition metal/metal oxides 3D microlattices is 2X lower (13.0 Q) than that of the single transition metal/metal oxides 3D microlattices (25.0 Q).
  • FIG. 26(b) displays the Nyquist plots.
  • Embodiments of the present disclosure include a rapid and robust polymer-infused additive manufacturing 3D printing method for fabricating transition metal-based electrocatalysts for alkaline electrolysis.
  • This example shows how the design of optimal 3D architectures and posttreatments yield microlattice electrodes with increased active sites and improved electrolytic properties of transition metal-based materials.
  • Overall, for alkaline HER Cu/CuOx/C has efficient electrocatalytic activity with low overpotential (145 mV to gain 10 mA/cm 2 ), and for OER Co/CoOx/C electrode demonstrates exceptional activity with the lowest overpotential (1.40 V to gain 10 mA/cm 2 ) among all reported PGM-free electrodes.
  • 3D microlattices of transition metal transition metal oxide/carbon [0125] First, the Kudo3D stereolithography system was utilized to print 3D polymer microlattices employing Kudo’s Ultra High Resolution (UHR) positive resin based on an acrylate photopolymer. This system can be used to produce lattices with features as small as 20 micron after post-annealing processes. 3D microlattices of transition metal/transition metal oxide/carbon are fabricated by simply polymer infusion additive manufacturing. Briefly, first 3D polymer microlattices were infiltrated by respective metal salts.
  • UHR Ultra High Resolution
  • XPS X-ray photoelectron spectroscopy
  • XRD powder X- ray diffraction
  • TEM transmission electron microscopy
  • SEM scanning electron microscopy
  • TGA thermogravimetric analysis
  • Bubble evolution experiments were performed with a high-speed video camera focused on a slab of microlattice or foam that was 3D printed by similar methods to those used for the catalysts.
  • Frame by frame analysis was used to assess the average bubble velocity in each respective lattice or foam system oriented perpendicular to the direction of buoyant force, an identical orientation to how each catalyst microlattice was tested electrochemically.
  • Electrochemical characterization was performed with a VersaSTAT electrochemical workstation from Princeton Applied Research equipped with a three-electrode system for studying the activity of the research for the Hydrogen Evolution Reaction (HER) and Oxygen Evolution Reaction (OER).
  • the setup included a working electrode consisting of the 3D microlattices, a reference electrode of Ag/AgCl in 3M KC1, and a counter electrode using Pt wire, all immersed in a 1.0 M KOH electrolyte solution.
  • the 3D microlattices functioned as the working electrode without requiring any additional additives or binders. All potentials were adjusted relative to a Reversible Hydrogen Electrode (RHE) using the following formula.
  • RHE Reversible Hydrogen Electrode
  • E(RHE) EAg/Agci + 0.059 pH + E°Ag/Agci, where E°Ag/Agci— 0.1976 V
  • the current was normalized based on the surface area of the calcined microlattices. Calculations of the microlattice surface area of the octet, BCC, and cubic lattices based on a graph theory model summing the surface of each individual strut element and accounting for beam intersections were utilized.

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Abstract

L'invention concerne une électrode d'électrocatalyseur présentant une structure en treillis de brins constituée d'un polymère et d'un composite qui est disposé sur la structure en treillis de brins et comprend au moins un oxyde de métal de transition, qui peut comprendre l'oxyde de cuivre, l'oxyde de cobalt ou l'oxyde de nickel. Le composite et la structure en treillis de brins sont tridimensionnels et autonomes. L'électrode d'électrocatalyseur comprend un ou plusieurs pores qui sont alignés verticalement pour former des canaux et pour faciliter la libération de bulles. Le composite est utilisé pour une réaction d'évolution d'hydrogène alcalin (HER) et une réaction d'évolution d'oxygène (OER).
PCT/US2024/033807 2023-06-13 2024-06-13 Électrodes en composite tridimensionnel nanoporeux à base de carbone et d'oxydes de métal de transition pour électrocatalyse efficace Ceased WO2024259099A2 (fr)

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