Palladium/Stannic Oxide Interfacial Chemistry Promotes Hydrogen Oxidation Reactions in Alkaline Medium

A nanostructured Pd/SnO(2)on metal-organic-framework-derived carbon (Pd/SnO2/MOFDC) electrocatalyst and its monometallic catalyst (Pd/MOFDC) have been synthesized by microwave-assisted strategies and investigated for the alkaline hydrogen oxidation reaction (HOR). Physical properties of the electrocatalysts are examined using X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller analysis, transmission electron microscopy, and density functional theory. This study reveals that the Pd/SnO2/MOFDC possesses superior alkaline HOR activities (in terms of kinetic current, heterogeneous rate constant, diffusivity, exchange current density, and the mass activity) compared to those of the Pd/MOFDC and that are comparable to commercial Pt/C. The improved alkaline HOR activity on Pd/SnO2/MOFDC is attributed to the facile interfacial electrochemical processes arising from the multifunctional properties of SnO(2)with the thin Sn film: i) weakening of Pd-H-ads, confirmed by DFT simulation, and ii) oxophilic (thin Sn film) and spill-over (SnO2) effects that quickly transfer OH(-)ions to the desorbed H(ads)for facile reaction in the Volmer rate-determining step (RDS). Tafel slope (b(a)=52-102 mV dec(-1)) and activation energy (E-A) values suggest the predominance of the Heyrovsky-Volmer process. In addition to the improved HOR activity of Pd/SnO2/MOFDC, it also exhibits better stability than Pd/MOFDC. The good performance of Pd/SnO2/MOFDC toward the alkaline HOR promises potential development of low-cost anode materials for alkaline membrane fuel cells.