TH99636A - Catalyst for electrochemical reduction of oxygen - Google Patents

Abstract

DC60 (12/05/51) This invention involves a sulfide catalyst for the electrochemical reduction of Stable oxygen, especially in chemically aggressive environments, such as those containing chlorinated hydrochloric acid. The catalyst according to this invention consists of a structural phase. A single crystal of a noble sulfide metal supported on conductive carbon. Which is mainly Free from zero valence metal phase And metal oxides. The catalyst is prepared by Reduce the metal pre-cursor salt. And the Taio pre-cursor with borohydride Or other strong reducing agents. This invention relates to sulfide catalysts for the electrochemical reduction of Stable oxygen In particular, chemically aggressive environments such as those containing chlorinated hydrochloric acid. This invention catalyst consists of a structural phase. A single crystal of a noble sulphide metal supported on conductive carbon, which is an integral part. Free from zero valence metal phase And metal oxides. The catalyst can be activated by Reduce the salt prompts the metal cursor. And the Taio pre-cursor with borohydride Or other strong reducing agents

Claims (13)

Revised 18/08/58 1. A catalyst for the electrochemical reduction of oxygen, consisting of a single crystal phase of a noble metal sulfide supported on conductive carbon, where the noble metal sulfide is rhodium or ruthenium sulfide, and the single crystal phase is (Pm-3m) Rh17S15 with a purity greater than 90%. 2. A catalyst according to claim 1 where the conductive carbon has a surface area in the range of 200 to 300 m²/g and a specific packing of the noble metal sulfide on the conductive carbon in the range of 12 to 18%. 3. A gas diffusion electrode incorporating one of the previously described catalysts on a conductive network. 4. A method for fabricating the catalyst according to claim 1 or 2, consisting of the following steps: - Inoculation of the noble metal precursor salt. At least one additional transition metal may be selected to react with the sulfur source under conditions where conductive carbon particles are present in the aqueous solution. The noble sulfide metals are then precipitated onto the conductive carbon particles by simultaneously or in a series of steps adding a reducing agent with a reduction potential lower than 0.14 V/SHE to the aqueous solution. The resulting slurry is then recovered and heat-treated in an inert gas atmosphere. Until a single crystal structure phase is obtained. 5. Method according to claim 4, where the sulfur source is thiosulfate or thionate species. 6. Method according to claim 4 or 5, where the noble metal is rhodium. 7. Method according to claim 4 or 5, where the noble metal is ruthenium and at least one additional metal is selected from the group consisting of W, Co, Mo, Ir, Rh, Cu, Ag, Hg. 8. Any one of the methods according to claim 4 to 7, where the slurry is recovered by filtration and the heat treatment is performed at a temperature in the range of 150-1250°C. 9. Any one of the methods according to claim 4 to 8. Where the reducing agent is NaBH4. 10. A catalyst resulting from any of the methods under claims 4 through 8. 11. A catalyst under claim 1 or 2 when used for the electrochemical reduction of oxygen. 1. A catalyst for the electrochemical reduction of oxygen, consisting of a single-crystal structure phase of noble metal sulfide supported on electrically conductive carbon. 2. The catalyst under claim 1, whereby the noble metal sulfide is rhodium or ruthenium sulfide. 3. The catalyst according to claim 2, where the single crystal structure phase is (Pm-3m)Rh17S15. 4. The catalyst under claim 2, where the noble metal sulfide is ruthenium sulfide and of additional transition metal M depending on the choice, and the single crystal structure phase is (Pa3)RuS2 or RuxMzSy. 5. Catalyst according to claim 4, where the additional transition metal is selected from the group containing W, Co, Mo, Ir, Rh, Cu, Ag, Hg. 6. A catalyst pursuant to any of the claims 3 through 5, where the aforementioned conductive carbon has a surface area in the range of 200 to 300 m²/g and a specific filling amount of such noble metal sulfide on such conductive carbon is in the range of 12 to 18%. 7. An electrode through which a gas is diffused, incorporating a catalyst according to one of the previously stated claims, is located on a conductive network. 8. A method for producing one of the catalysts under claims 1 through 6, which includes the following steps: - Reaction of noble metal and at least one additional transition metal precursor salt, depending on the choice, with a sulfur source under conditions where conductive carbon particles are in an aqueous solution. - Precipitation of such noble metal sulfides on such conductive carbon particles by adding a reducing agent with a reduction potential less than 0.14 V/SHE into the aqueous solution simultaneously with the addition of the sulfur source, or in a subsequent step after the addition of the sulfur source. - Recovery and heat treatment of the resulting slurry in an inert gas atmosphere until a single crystalline phase is obtained. 9. Methods under claim 8, where the sulfur source is the thiosulfate or thionate species. 10. The method under claim 8 or 9, where the noble metal is rhodium. 11. The method under claim 8 or 9, where the noble metal is ruthenium and at least one additional metal is selected from a group consisting of W, Co, Mo, Ir, Rh, Cu, Ag, Hg. 12. Any of the methods under claims 8 through 11, whereby the slurry is recovered by filtration and heat treatment is carried out at temperatures in the range of 150–1250°C. 13. Any of the methods under claims 8 through 12, where the reducing agent is NaBH4.