Cathode for hydrogen generation and method for producing the same
The present invention provides an excellent durable cathode for hydrogen generation, which has a low hydrogen overvoltage and reduced dropping-off of a catalyst layer against the reverse current generated when an electrolyzer is stopped, and a method for producing the same. The present invention provides a cathode for hydrogen generation having a conductive base material and a catalyst layer formed on the conductive base material, wherein the catalyst layer includes crystalline iridium oxide, platinum and iridium-platinum alloy.
1. A cathode for hydrogen generation having a conductive base material and a catalyst layer formed directly on said conductive base material, wherein said catalyst layer comprises crystalline iridium oxide, platinum and iridium-platinum alloy,
wherein said conductive base material is formed of nickel, and
wherein, in the X-ray diffraction measurement, said crystalline iridium oxide gives a diffraction peak which is observed in an angular region including 2θ=34.70° and has a full width at half maximum of 0.47° or less.
2. The cathode for hydrogen generation according to claim 1 , wherein a ratio (Pt/(Ir+Pt)) of mole number of said platinum element to total mole number of iridium element and platinum element present in said catalyst layer is 20 to 50% by atom.
3. An electrolyzer for electrolysis of an alkali metal chloride, equipped with the cathode for hydrogen generation having a conductive base material and a catalyst layer formed on said conductive base material, wherein said catalyst layer comprises crystalline iridium oxide, platinum and iridium-platinum alloy.
4. A method for producing the cathode for hydrogen generation according to claim 1 , comprising:
a coating step to apply an application liquid comprising an iridium compound and a platinum compound directly onto the conductive base material formed of nickel;
a film-forming step to form a coated film by drying said application liquid;
a thermal decomposition step to heat said coated film to decompose thermally; and
an electrolyzing step to electrolyze the coated film after said thermal decomposition.
5. The method for producing the cathode for hydrogen generation according to claim 4 , wherein a ratio (Pt/(Ir+Pt)) of mole number of said platinum element to a total mole number of iridium element and platinum element present in said application liquid is 20 to 50% by atom.
6. The method for producing the cathode for hydrogen generation according to claim 4 , wherein a cycle composed of said coating step, said film-forming step, and said thermal decomposition step is repeated two or more times.
7. The method for producing the cathode for hydrogen generation according to claim 4 , wherein, in said thermal decomposition step, said thermal decomposition is carried out at a temperature of 470° C. or higher and 600° C. or lower.
8. The method for producing the cathode for hydrogen generation according to claim 4 , wherein, in said film-forming step, drying of said application liquid is carried out at a temperature of 200° C. or lower.
9. A method for producing the cathode for hydrogen generation having a conductive base material and a catalyst layer formed on said conductive base material, wherein said catalyst layer comprises crystalline iridium oxide, platinum and iridium-platinum alloy, the method comprising:
a coating step to apply an application liquid comprising an iridium compound and a platinum compound onto the conductive base material;
a film-forming step to form a coated film by drying said application liquid;
a thermal decomposition step to heat said coated film to decompose thermally; and
an electrolyzing step to electrolyze the coated film after said thermal decomposition,
wherein, in said thermal decomposition step, the coated film is subjected to post-heat treatment in an inert gas atmosphere after said thermal decomposition.
10. A method for producing the cathode for hydrogen generation having a conductive base material and a catalyst layer formed on said conductive base material, wherein said catalyst layer comprises crystalline iridium oxide, platinum and iridium-platinum alloy, the method comprising:
a coating step to apply an application liquid comprising an iridium compound, a platinum compound, an organic acid having a valence of two or more, and an organic compound having two or more hydroxyl groups subjected to an esterification reaction with said organic acid, onto the conductive base material;
a film-forming step to form a coated film by drying said application liquid; and
a thermal decomposition step to heat said coated film to decompose thermally.