Synergism of molybdenum nitride and palladium for high-efficiency formic acid electrooxidation

Abstract

The direct formic acid fuel cell (DFAFC) has received increasing attention in the sustainable and clean energy field. However, the high cost, poor durability, and shortage of palladium (Pd) based catalysts for the formic acid oxidation reaction (FAOR) restrict the large-scale application of DFAFC. Herein, molybdenum nitride/reduced graphene oxide (Mo₂N/rGO) was designed as an effective cocatalyst of Pd for FAOR based on an assembly-immobilization method. It is shown that the small-sized Mo₂N is well dispersed on rGO with high density, which is favorable for the post-loading deposition of Pd onto the rGO to form a strongly coupled Pd–Mo₂N structure. The strong interaction between Pd and Mo₂N, verified by a series of characterizations, is helpful for promoting the performance of Pd. Electrochemical tests indicate that the Pd–Mo₂N/rGO catalyst shows superior activity to other Pd based catalysts, with a current density of 532.7 mA mg_Pd⁻¹, which is 1.7 and 2.2 times greater than those of Pd/reduced graphene oxide (Pd/rGO) and Pd/Vulcan XC-72 (Pd/VC), respectively. In addition, Pd–Mo₂N/rGO exhibits enhanced CO tolerance and good stability. The good performance is mainly ascribed to the intimate contact between Mo₂N and Pd which gives enhanced synergistic action. The excellent performance of Pd–Mo₂N/rGO makes it a potential electrocatalyst for DFAFC applications.