Effect of core-alloy composition and particle size of stabilized Pt Skin/PtCo alloy nanocatalysts on the CO-Tolerant hydrogen oxidation electrocatalysis

Abstract We have, for the first time, examined the effects of core-alloy composition and particle-size of Pt100−xCox alloy nanocatalysts with a stabilized Pt-skin (one to two atomic layers) supported on carbon black (PtxAL‒Pt100-xCox/C) on the activities for the hydrogen oxidation reaction (HOR) and its tolerance of low levels of CO. The optimum composition for the HOR was found in the range x = 30 to 50 atom%. Such a dependency was correlated with an optimal adsorption strength for atomic hydrogen on (111) terraces according to DFT calculations. The CO tolerance trend was explained based on weakened adsorption of CO on step and terrace sites. It was found that the smallest particles retained high CO-tolerant HOR activity during the accelerated durability test, enabling the alloy nanoparticles as small as 2.2 nm to be very promising for increased mass activity in polymer electrolyte fuel cells with reformate fuel as well as pure H2.