Rare-earth oxide promoted Pd electrocatalyst for formic acid oxidation

Abstract

The development of Pd-based materials with high activity and long-term stability is crucial for their practical applications as an anode catalyst in direct formic acid fuel cells. Herein, we reveal that the catalytic activity of Pd towards formic acid oxidation can be enhanced by incorporation of a series of rare-earth oxides, including Sc₂O₃, CeO₂, La₂O₃, and Pr₂O₃. For example, Pd nanoparticles incorporated with Sc₂O₃ supported on nitrogen-doped reduced graphene oxide (Pd-Sc₂O₃/N-rGO-x, x = 1/3, 1/2, 2/3, 1, and 3/2; “x” denotes the molar ratio of Pd : Sc) can be obtained using a sodium borohydride reduction method. When directly used as an electrocatalyst towards formic acid oxidation (FAO), Pd-Sc₂O₃/N-rGO-2/3 exhibits the highest mass current density of 972.9 mA mg_Pd⁻¹, surpassing that of the reference catalysts Pd/C (262.6 mA mg_Pd⁻¹) and Pd/N-rGO (304.9 mA mg_Pd⁻¹). More importantly, the Pd-Sc₂O₃/N-rGO-2/3 catalyst demonstrates high CO tolerance and long-term stability in the FAO reaction. The improved electrooxidation activity and stability could be attributed to the synergistic effect between Sc₂O₃ and Pd nanoparticles. Therefore, this study presents a crucial contribution to the advancement of various rare-earth oxides in enhancing Pd activity towards FAO and beyond.