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The electrocatalytic conversion of formate in alkaline solutions is of paramount significance in the realm of fuel cell applications. Nonetheless, the adsorptive affinity of adsorbed hydrogen (H ad ) on the catalyst surface has traditionally impeded the catalytic efficiency of formate in such alkaline environments. To circumvent this challenge, our approach introduces an interfacial push-pull effect on the catalyst surface. This mechanism involves two primary actions: First, the anchoring of palladium (Pd) nanoparticles on a phosphorus-doped TiO 2 substrate (Pd/TiO 2 -P) promotes the formation of electron-rich Pd with a downshifted d band center, thereby "pushing" the desorption of H ad from the Pd active sites. Second, the TiO 2 -P support diminishes the energy barrier for H ad transfer from the Pd sites to the support itself, "pulling" H ad to effectively relocate from the Pd active sites to the support. The resultant Pd/TiO 2 -P catalyst showcases a remarkable mass activity of 4.38 A mg Pd -1 and outperforms the Pd/TiO 2 catalyst (2.39 A mg Pd -1 ) by a factor of 1.83. This advancement not only surmounts a critical barrier in catalysis but also delineates a scalable pathway to bolster the efficacy of Pd-based catalysts in alkaline media.

This study addresses the critical challenge in alkaline direct formate fuel cells (DFFCs) of slow formate oxidation reaction (FOR) kinetics as a result of strong hydrogen intermediate (H ad ) adsorption on Pd catalysts. We developed WO 3 -supported Pd nanoparticles (EG-Pd/WO 3 ) via an organic reduction method using ethylene glycol (EG), aiming to modulate the d-band center of Pd and alter H ad adsorption dynamics. Cyclic voltammetry demonstrated significantly improved H ad desorption kinetics in EG-Pd/WO 3 catalysts. Density functional theory (DFT) calculations revealed that the presence of EG reduces the d-band center of Pd, leading to weaker Pd-H bonds and enhanced H ad desorption during the FOR. This research provides a new approach to optimize catalyst efficiency in DFFCs, highlighting the potential for more effective and sustainable energy solutions through advanced material engineering.

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 (H ad ). 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-H ad in alkaline media. Notably, Cu plays a pivotal role in bolstering the concentration of hydroxyl adsorbates (OH ad ) on the surface of catalyst. These OH ad species can react with H ad , 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 (OH ad ) at diminished potentials. This, in turn, aids the oxidative removal of Pd-H ad , 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 OH ad , ensuring efficient removal of H ad . This work paves the way, shedding light on the strategic design of high-performing FOR catalysts.