Oxygen reduction catalyst and method for producing same

Patent metadata

Field	Value
Publication number	US-9947936-B2
Application number	US-201214371568-A
Country	US
Kind code	B2
Filing date	Jul 19, 2012
Priority date	Jan 13, 2012
Publication date	Apr 17, 2018
Grant date	Apr 17, 2018

Abstract

The present invention concerns an oxygen reduction catalyst comprising composite particles in which primary particles of a titanium compound is dispersed into a carbon structure, wherein the composite particles have titanium, carbon, nitrogen and oxygen as constituent elements, and with regard to a ratio of number of atoms of each of the elements when titanium is taken as 1, a ratio of carbon is larger than 2 and 5 or less, a ratio of nitrogen is larger than 0 and 1 or less, and a ratio of oxygen is 1 or more and 3 or less, and an intensity ratio (D/G ratio) of D band peak intensity to G band peak intensity in a Raman spectrum is in the range of 0.4 to 1.0. The oxygen reduction catalyst according to the present invention has satisfactory initial performance and excellent start-stop durability.

First claim

The invention claimed is:

1. An oxygen reduction catalyst comprising composite particles in which primary particles of a titanium compound are dispersed into a carbon structure, wherein
the composite particles have titanium, carbon, nitrogen and oxygen as constituent elements, and with regard to a ratio of number of atoms of each of the elements when titanium is taken as 1, a ratio of carbon is larger than 2 and 5 or less, a ratio of nitrogen is larger than 0 and 1 or less, and a ratio of oxygen is 1 or more and 3 or less, and
an intensity ratio (D/G ratio) of the composite particles of D band peak intensity to G band peak intensity in a Raman spectrum is in the range of 0.4 to 1.0.

2. The oxygen reduction catalyst according to claim 1 , wherein the composite particles further comprise at least one kind of element M2 selected from iron, nickel, chromium, cobalt and manganese, and a ratio of number of atoms of total amount of element M2 to titanium is in the range of 0.3 or less.

3. The oxygen reduction catalyst according to claim 1 , wherein the composite particles have a peak, in X-ray diffraction (XRD) measurement using a Cu-Kα line, in each of regions A to D of a 2θ range described below:
A: 26 to 28°;
B: 35 to 37°;
C: 40 to 42°; and
D: 53 to 55°, and
have a peak with the highest intensity of all the peaks that appear in a diffraction pattern in the region A.

4. The oxygen reduction catalyst according to claim 1 , wherein a valence of titanium determined from a transmission X-ray absorption fine structure analysis (transmission XAFS) of the composite particles is larger than 3 and less than 4.

5. The oxygen reduction catalyst according to claim 1 , further having particles comprising a noble metal or a noble metal alloy supported on the composite particles.

6. The oxygen reduction catalyst according to claim 5 , wherein the noble metal includes at least one kind of noble metal selected from platinum, palladium, iridium, rhodium and ruthenium.

7. The oxygen reduction catalyst according to claim 5 , wherein the particles comprise the noble metal alloy and the noble metal alloy includes an alloy comprising noble metals, or a noble metal and at least one kind of metal selected from iron, nickel, chromium, cobalt, titanium, copper, vanadium and manganese.

8. An ink for preparing a catalyst layer for a fuel cell, comprising the oxygen reduction catalyst according to claim 1 .

9. A catalyst layer for a fuel cell, prepared using the ink for preparing the catalyst layer for the fuel cell according to claim 8 .

10. An electrode for a fuel cell, comprising the catalyst layer for the fuel cell according to claim 9 .

11. A membrane-electrode assembly, comprising a cathode catalyst layer and an anode catalyst layer, and a polymer electrolyte membrane arranged between both the catalyst layers, wherein the cathode catalyst layer and/or the anode catalyst layer is the catalyst layer for the fuel cell according to claim 9 .

12. A fuel cell, comprising the membrane-electrode assembly according to claim 11 .

13. A method for producing the oxygen reduction catalyst according to claim 1 , comprising:
Step 1 for mixing a titanium-containing compound (1), a nitrogen-containing organic compound (2) and a solvent to give a catalyst precursor solution;
Step 2 for removing the solvent from the catalyst precursor solution to give a solid residue;
Step 3 for heat-treating the solid residue obtained in Step 2 at a temperature of 700° C. to 1,400° C. to give a heat-treated material; and
Step 4 for applying oxidation treatment of the heat-treated material obtained in Step 3 with an oxidizing agent giving an oxygen atom, wherein at least one of the titanium-containing compound (1) and the nitrogen-containing organic compound (2) has an oxygen atom, and oxidization in Step 4 is adjusted to render a D/G ratio in the range of 0.4 to 1.0.

14. The method for producing the oxygen reduction catalyst according to claim 13 , wherein the oxidizing agent giving the oxygen atom is at least one kind selected from water, hydrogen peroxide, perchloric acid and peracetic acid.

15. The method for producing the oxygen reduction catalyst according to claim 13 , wherein Step 4 overlaps with Step 3 and is applied after or at the same time as start of Step 3.

16. The method for producing the oxygen reduction catalyst according to claim 15 , wherein the oxidizing agent used in a part of Step 4, which overlaps with Step 3, is water.

17. The method for producing the oxygen reduction catalyst according to claim 15 , wherein Step 4 is applied even after end of Step 3.

18. The method for producing the oxygen reduction catalyst according to claim 17 , wherein the oxidizing agent used in a part of Step 4, which is applied after end of Step 3, is at least one kind selected from hydrogen peroxide, perchloric acid, and peracetic acid.

Assignees

• Tezuka Noriyasu
• Horikita Masaki
• Yoshimura Masayuki
• Ito Yuji
• Sato Takashi
• Showa Denko Kk

Inventors

• Tezuka Noriyasu
• Horikita Masaki
• Yoshimura Masayuki
• Ito Yuji
• Sato Takashi

Classifications

• H01M2008/1095

  Fuel cells with polymeric electrolytes · CPC title

• H01M4/90

  Selection of catalytic material · CPC title

• H01M4/9016

  Oxides, hydroxides or oxygenated metallic salts · CPC title

• H01M4/8652 Primary

  as mixture · CPC title

• H01M4/9041 Primary

  Metals or alloys (H01M4/92 takes precedence) · CPC title