Catalyst Layer
A catalyst layer comprising an electrocatalyst and an oxygen evolution catalyst, wherein the oxygen evolution catalyst comprises a crystalline metal oxide comprising: (i) one of more first metals selected from the group consisting of yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, magnesium, calcium, strontium, barium, sodium, potassium, indium, thallium, tin, lead, antimony and bismuth; (ii) one or more second metals selected from the group consisting of Ru, Ir, Os and Rh; and (iii) oxygen characterised in that: (a) the atomic ratio of first metal(s):second metal(s) is from 1:1.5 to 1.5:1 (b) the atomic ratio of (first metal(s)+second metal(s)):oxygen is from 1:1 to 1:2 is disclosed.
1 . A catalyst layer comprising an electrocatalyst and an oxygen evolution catalyst, wherein the oxygen evolution catalyst comprises a crystalline metal oxide of formula
(AA′) a (BB′) b O c .
wherein A and A′ are the same or different and are selected from the group consisting of yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, magnesium, calcium, strontium, barium, sodium, potassium, indium, thallium, tin, lead, antimony and bismuth; B is selected from the group consisting of Ru, Ir, Os, and Rh; B′ is selected from the group consisting of Ru, Ir, Os, Rh, Ca, Mg or RE (wherein RE is a rare earth metal), indium, thallium, tin, lead, antimony and bismuth; c is from 3-11; the atomic ratio of (a+b):c is from 1:1 to 1:2; the atomic ratio of a:b is from 1:1.5 to 1.5:1.
2 . The catalyst layer according to claim 1 , wherein a is 0.66 to 1.5; b is 1; and c is 3 to 5.
3 . The catalyst layer according to claim 1 , wherein a is 2 to 4.5; b is 3; and c is 10 to 11.
4 . The catalyst layer according to claim 1 , wherein the oxygen evolution catalyst and the electrocatalyst are in separate layers in the membrane electrode assembly.
5 . The catalyst layer according to claim 1 , wherein the oxygen evolution catalyst and the electrocatalyst are in a single layer in the membrane electrode assembly.
6 . The catalyst layer according to claim 5 , wherein the oxygen evolution catalyst acts as a support material for the electrocatalyst.
7 . An electrode comprising a gas diffusion layer and a catalyst layer according to any one of claim 1 .
8 . A catalysed membrane comprising a proton conducting membrane and a catalyst layer according to claim 1 .
9 . A catalysed transfer substrate comprising a catalyst layer according to claim 1 .
10 . A membrane electrode assembly comprising a catalyst layer according to claim 1 .
11 . A fuel cell comprising a catalyst layer according to claim 1 .