Modulating the Interfacial Water Network of Dual-Site Pd/FeOx/C Catalyst for Efficient Formate Electrooxidation

The rational design of electrocatalysts for formate oxidation reaction (FOR) in alkaline media is crucial to promote the practical applications of direct formate fuel cells (DFFCs). The FOR kinetic on palladium (Pd) based electrocatalysts is strongly hindered by unfavorably adsorbed hydrogen (H_ad) as the major intermediate species blocking the active sites. Herein, we report a strategy of modulating the interfacial water network of dual-site Pd/FeO_x/C catalyst to significantly enhance the desorption kinetics of H_ad during FOR. Aberration-corrected electron microscopy and synchrotron characterizations revealed the successful construction of Pd/FeO_x interfaces on carbon support as a dual-site electrocatalyst for FOR. Electrochemical tests and in situ Raman spectroscopy results showed that H_ad could be effectively removed from the active sites of the as-designed Pd/FeO_x/C catalyst. CO-stripping voltammetry and density functional theory calculations (DFT) demonstrated that the introduced FeO_x could effectively accelerate the dissociative adsorption of water molecules on active sites, which accordingly generates adsorbed hydroxyl species (OH_ad) to facilitate the removal of H_ad during FOR. This work provides a novel route to develop advanced FOR catalysts for fuel cell applications.