(Invited) Enhanced Hydrogen Oxidation Activity at Pt-M Alloy Catalysts in Acid: A DFT Study

Abstract

Platinum alloys that include first-row transition metals have been examined extensively as CO-tolerant catalysts for the hydrogen oxidation reaction (HOR) in acidic media. The CO tolerance stems from the decreased CO adsorption strength, so that the surface is not easily poisoned. Recently, we have found experimentally that the intrinsic, area-specific HOR activity is also significantly enhanced for stabilized Pt-Co nanoparticle catalysts in aqueous acid solution.1 This is an aspect of the catalysis that has been little studied. We have found that the enhanced HOR activity is consistent with high-quality density functional theory (DFT) calculations, which show that the adsorption of underpotentially deposited (UPD) hydrogen atoms is weakened by the presence of the alloying metal under the (110) surface, which has been recognized to be the most active (Fig. 1). DFT calculations of Ishikawa and coworkers have explained the high activity of the Pt(110) surface as being due to the ease of H2 dissociation, with the rate-determining step being the desorption of HUPD.2 In addition, we have found recently that Pt-Fe and Pt-Ni catalysts also exhibit enhanced area-specific HOR activities, in addition to their enhanced CO tolerance, as will be presented by G. Shi separately. In particular, we found that the DFT calculated adsorption strength of HUPD on the Pt-Fe nanoparticle (110) surface is greatly weakened, consistent with its high HOR activity. Nevertheless, H2 dissociation remains facile. Acknowledgements This work has been supported by the Superlative, Stable, and Scalable Performance Fuel Cell (SPer-FC) project funded by the New Energy and Industrial Development Organization (NEDO) of Japan. References G. Shi, H. Yano, D. A. Tryk, M. Watanabe, A. Iiyama, and H. Uchida, A novel Pt-Co alloy hydrogen anode catalyst with superlative activity, CO-tolerance and robustness, Nanoscale, 2016, DOI: 10.1039/C6NR00778C.J. Santana, J. J. Mateo, and Y. Ishikawa, Electrochemical hydrogen oxidation on Pt(110): a combined direct molecular dynamics/density functional theory study, J. Phys. Chem. C, 114, 4995-5002 (2010). Figure 1