NiMoO₄ With High Oxidation States for Efficient Electrooxidation of Amines to Nitriles

Electrochemical oxidation of amines to nitriles, with water as the O source, is a green and sustainable route to synthesize nitriles under mild conditions. However, developing highly efficient electrocatalysts for amine oxidation with large current densities is quite challenging. Herein, it is demonstrated that NiMoO₄ with high oxidation states can efficiently catalyze benzylamine oxidation reaction (BAOR) to benzonitrile (BN) with a large anodic current density of 300.0 mA cm^-2 at 1.47 V versus RHE. Impressively, NiMoO₄ simultaneously achieves high BA conversion, BN selectivity, and faradaic efficiency of BN above 95%, together with a large BN yield of 0.366 mmol h^-1 at 1.45 V versus RHE. Such excellent performance is also verified in a practical continuous-flow membrane electrode assembly reactor. Electrochemical measurements and in situ techniques uncover that NiOOH is the catalytically active species for BAOR, while the generation of NiOOH is more facile and effective on NiMoO₄ than on Ni(OH)₂. Theoretical calculations reveal that Mo doping in NiOOH facilitates the adsorption of BA, and reduces the energy barriers for the subsequent dehydrogenation steps, leading to excellent BAOR performance.