Use of an anode catalyst layer

A method of operating a fuel cell comprising an anode, a cathode and a polymer electrolyte membrane disposed between the anode and the cathode, wherein said method comprises feeding the anode with an impure hydrogen stream comprising carbon monoxide in an amount of between 2 ppm to 5 ppm, and wherein the anode comprises an anode catalyst layer comprising a carbon monoxide tolerant catalyst material, wherein the catalyst material comprises:

• (i) a binary alloy of PtX, wherein X is rhodium, and wherein the atomic percentage of platinum in the alloy is from 45 to 80 atomic % and the atomic percentage of X in the alloy is from 20 to 55 atomic %;
• and
• (ii) a support material on which the PtX alloy is dispersed;
• wherein the total loading of platinum group metals (PGM) in the anode catalyst layer is from 0.01 to 0.2 mgPGM/cm2, wherein the fuel cell produces stable voltages when the anode is fed an impure catalyst stream comprising 5 ppm of carbon monoxide.