Catalyst

Abstract

Disclosed herein are electrocatalyst materials for an anode catalyst, wherein the electrocatalyst material comprises a carbon support material, the carbon support material comprising a plurality of individual support particles or aggregates, wherein each individual support particle or aggregate has dispersed thereon separate (i) first particles and (ii) second particles. Also provided are processes for forming such electrocatalyst materials, as well as anode catalysts comprising the electrocatalyst materials.

What is claimed: 
     
         1 . An electrocatalyst material for an anode catalyst, wherein the electrocatalyst material comprises a carbon support material, the carbon support material comprising a plurality of individual support particles or aggregates, wherein each individual support particle or aggregate has dispersed thereon separate (i) first particles and (ii) second particles, wherein:
 (i) the first particles consist of Pt or comprise Pt alloyed with an alloying metal X1, wherein the alloying metal X1 is selected from the group consisting of Rh, Os, V, Co, Ni, Ga, Hf, Sn, Ir, Pd, Mo, Zn, W, Zr and Re;   (ii) the second particles consist essentially of a second metal or a second metal compound, wherein the second metal is Ru and the second metal compound comprises IrX2, wherein X2 is selected from the group consisting of Ta, Nb, Ru, Ni and Co; and   wherein if the first particles consist of Pt, then the second particles consist of Ru.   
     
     
         2 . The electrocatalyst material according to  claim 1 , wherein X1 is selected from the group consisting of Rh, Os, V, Hf, Sn, Pd, Mo, W, Zr and Re. 
     
     
         3 . The electrocatalyst material according to  claim 1 , wherein X1 is selected from the group consisting of Rh and Mo. 
     
     
         4 . The electrocatalyst material according to  claim 1 , wherein X2 is selected from the group consisting of Ta, Nb and Ru. 
     
     
         5 . The electrocatalyst material according to  claim 1 , wherein the first particles consist of Pt and the second particles consist of Ru. 
     
     
         6 . The electrocatalyst material according to  claim 1 , wherein the first particles comprise Pt alloyed with the alloying metal X1 and the second particles consist essentially of Ru. 
     
     
         7 . The electrocatalyst material according to  claim 1 , wherein the first particles comprise Pt alloyed with the alloying metal X1 and the second particles consist essentially of IrX2. 
     
     
         8 . The electrocatalyst material according to  claim 1 , wherein each individual support particle or aggregate of the support material of the electrocatalyst material has dispersed thereon only first and second particles. 
     
     
         9 . The electrocatalyst material according to  claim 1 , wherein the electrocatalyst material comprises first particles consisting of Pt alloyed with Rh; and second particles consisting essentially of IrX2. 
     
     
         10 . The electrocatalyst material according to  claim 9 , wherein X2 is Ru. 
     
     
         11 . The electrocatalyst material according to  claim 1 , wherein the ratio of first metal to alloying metal X1 is from 5:1 to 1:5. 
     
     
         12 . The electrocatalyst material according to  claim 1 , wherein the first particles have a mean average particle size in the range of from 2 to 14 nm. 
     
     
         13 . The electrocatalyst material according to  claim 1 , wherein the second particles have a mean average particle size in the range of from 0.5 to 10 nm. 
     
     
         14 . The electrocatalyst material according to  claim 1  in an electrochemical cell, optionally wherein the electrochemical cell is a fuel cell. 
     
     
         15 . The electrocatalyst material according to  claim 1 , wherein:
 (i) the first particles comprise Pt alloyed with an alloying metal X1;    wherein the alloying metal X1 is selected from the group consisting of Rh, Os, V, Co, Ni, Hf, Sn, Ir, Pd, Mo, Zn, W, Zr and Re; and   (ii) the second particles consist essentially of Ru or a second metal compound comprising IrX2 wherein X2 is selected from the group consisting of Ta, Nb, Ru.   
     
     
         16 . A process for the preparation of an electrocatalyst material according to  claim 1 , said process comprising the steps of:
 (A) forming a precursor A comprising the support material and the first particles by
 (i) depositing Pt onto the support material to form a first precursor; and, 
 (ii) optionally depositing an alloying metal X1 onto the first precursor to form a second precursor; and annealing the first precursor and second precursor, 
 thereby forming the precursor A; and 
   (B) forming a precursor B comprising the support material and the second particles by
 (i) depositing Ru onto the support material to form a third precursor; or 
 (ii) depositing Ir and X2 onto the support material to form a fourth precursor; and annealing the fourth precursor, 
 thereby forming the precursor B; 
   wherein steps (A) and (B) are carried out in any order.   
     
     
         17 . The process according to  claim 16 , wherein step (A) is carried out before step (B). 
     
     
         18 . The process according to  claim 16 , wherein step (B) comprises depositing the second metal or second metal compound using pre-formed metal or metal alloy nanoparticles suspended in solution. 
     
     
         19 . The process according to  claim 16 , comprising an additional step after either of annealing steps (A)(ii) and/or (B)(ii) in which the precursor A or B is subjected to an acid wash prior to any subsequent depositing step (A)(i) and/or (B)(i). 
     
     
         20 . An anode catalyst comprising the electrocatalyst material according to  claim 1 .