Direct formate fuel cells have gained traction due to their eco-friendly credentials and inherent safety. However, their potential is hampered by the kinetic challenges of the formate oxidation reaction (FOR) on Pd-based catalysts, chiefly due to the unfavorable adsorption of hydrogen species (Had). These species clog the active sites, hindering efficient catalysis. Here, we introduce a straightforward strategy to remedy this bottleneck by incorporating Pd with Cu to expedite the removal of Pd–Had in alkaline media. Notably, Cu plays a pivotal role in bolstering the concentration of hydroxyl adsorbates (OHad) on the surface of catalyst. These OHad species can react with Had, effectively unblocking the active sites for FOR. The as-synthesized catalyst of PdCu/C exhibits a superior FOR performance, boasting a remarkable mass activity of 3.62 A mg–1. Through CO-stripping voltammetry, we discern that the presence of Cu in Pd markedly speeds up the formation of adsorbed hydroxyl species (OHad) at diminished potentials. This, in turn, aids the oxidative removal of Pd–Had, leveraging a synergistic mechanism during FOR. Density functional theory computations further reveal intensified interactions between adsorbed oxygen species and intermediates, underscoring that the Cu–Pd interface exhibits greater oxyphilicity compared to pristine Pd. In this study, we present both experimental and theoretical corroborations, unequivocally highlighting that the integrated copper species markedly amplify the generation of OHad, ensuring efficient removal of Had. This work paves the way, shedding light on the strategic design of high-performing FOR catalysts.
To improve the electrocatalytic activity of catalysts for ethanol oxidation, PtxAuy/SnO2GN with a double-junction structure of PtxAuy and SnO2 is designed and synthesized, in which the atom ratios of Pt and Au are 1:0, 1:1, 1:2, 1:3, 1:4, and 1:5. Raman spectroscopy, Brunauer–Emmet–Teller method, X-ray diffraction, transmission electron micrography, and X-ray photoelectron spectroscopy are used to characterize the prepared catalysts. It is found that Pt and Au form an alloy, and the alloy is uniformly distributed around SnO2 on graphene (GN). The catalytic properties of PtxAuy/SnO2GN for ethanol electrooxidation are studied by electrochemical tests such as cyclic voltammetry, linear sweep voltammetry, chronoamperometry, and CO stripping. The results show that Pt1Au3/SnO2GN has the largest electrochemically activated surface area (ECSA), the lowest ethanol oxidation onset potential, the highest ethanol oxidation peak current density, and the best ethanol oxidation stability. Combined with electrochemical in situ infrared spectroscopy, the excellent catalytic performance of Pt1Au3/SnO2GN is attributed to its unique double-junction structure of PtAu alloy and SnO2 on GN enhancing the tolerance to CO-like toxic species, as well as the alloy of Pt and Au and their appropriate atomic ratio properly changing the electronic structure of Pt and increasing the ECSA, which are conducive to the easier electrooxidation of ethanol.
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