Effects of Composition and Annealing Conditions on Catalytic Activities of Dealloyed Pt–Cu Nanoparticle Electrocatalysts for PEMFC

Dealloyed bimetallic nanoparticle electrocatalysts exhibit up to six times higher oxygen reduction reaction activities than pure nanoparticle Pt catalysts at / reversible hydrogen electrode (RHE). The active form of the catalyst is formed in situ from Pt–Cu precursor material using voltammetric dealloying. The effects of composition of precursors as well as effects of the annealing temperature and duration on the catalyst activity are studied. We vary the composition between and and change the annealing conditions from and for 7 and . X-ray diffraction and electrochemical analyses are used to obtain insight on the structural details of the catalyst samples. Information regarding the extent of alloying, atomic ordering, the Pt and Cu compositions, and distributions on the nanoparticles and particle (crystallite) sizes is correlated with the trends observed from mass and specific activities of the catalysts. It was found that an annealing duration of offers little or no benefit to catalytic activities compared to . Dealloyed annealed for , at yielded an optimal active material with respect to the extent of alloying and particle size growth and exhibited the highest Pt mass-based and favorable specific catalytic oxygen reduction reaction (ORR) activity. The occurrence and role of a noncubic Hongshiite phase is discussed.