Rare-earth oxides promoted Pd electrocatalyst for formic acid oxidation

Abstract

The development of Pd-based materials with high activity and long-term stability are 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 a series of rare-earth oxide, including Sc2O3, CeO2, La2O3, and Pr2O3, etc. As an example, the 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, 3/2; "x" denotes the molar ratio of Pd: Sc) can be obtained using sodium borohydride reduction method. When directly used Pd-Sc2O3/N-rGO-2/3 as an electrocatalyst towards formic acid oxidation (FAO). The Pd-Sc2O3/N-rGO-2/3 shows the highest mass current density of 972.9 mA mg-1Pd, surpassing that of the reference catalysts Pd/C (262.6 mA mg-1Pd) and Pd/N-rGO (304.9 mA mg-1Pd). More importantly, the Pd-Sc2O3/N-rGO-2/3 catalyst also shows high CO tolerance and long-term stability in 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 for enhancing Pd activity towards FAO and beyond.