Enhanced Electrocatalytic Oxidation of Formate via Introducing Surface Reactive Oxygen Species to a CeO₂ Substrate

Direct formate fuel cells (DFFCs) as promising energy technologies have been applied for portable and wearable devices. However, for the formate oxidation reaction (FOR), the deficiency of catalysts has prevented DFFCs from practical applications. Herein, we prepared a Pd-loaded CeO₂ catalyst through a simple steam treatment at 400 °C to enhance the catalytic FOR performance. In comparison with the counterpart of Pd/CeO₂ without stream treatment, the as-prepared Pd/CeO₂-ST catalyst has a lower onset potential of 381 mV and a lower peak potential of 0.64 V with a higher peak current of 10.62 mA cm^-2. The experimental results show that the enhanced FOR properties of Pd/CeO₂-ST are ascribed to the introduction of surface reactive oxygen species to the CeO₂ substrate, which substantially promotes the desorption of adsorbed hydrogen (H*) intermediates. Density functional theory (DFT) calculations reveal that on the surface of CeO₂, the abundant oxygen vacancies boost the OH* adsorption ability and accelerate the kinetics of the potential-limiting step. This work not only proposes a new strategy for enhancing the activity of FOR catalysts but also highlights the understanding of the FOR mechanism in alkaline media for DFFC applications.