Kinetic Understanding\nof Metal Ions Doping in Enhancing\nthe Electrocatalytic Ethanol Oxidation Performance of Nickel Hydroxides

Developing highly efficient electrocatalysts for organic\nelectrosynthesis\nsuch as the nucleophile oxidation reaction (NOR) is of great significance\nfor renewable energy utilization. However, the kinetic understanding\nof nickel-based catalysts in NOR still needs to be clarified. Herein,\nwe synthesized several metal ions-doped Ni(OH)<sub>2</sub> and studied\nthe mechanism of metal ions doping in enhancing the electrocatalytic\nNOR performance. Ethanol oxidation reaction (EOR) was used as a model\nreaction and a series of electrochemical measurements for the reaction\norder, electron transfer process, and metal redox kinetics of Ni(II)/Ni(III)\nwere combined with the electronic structural characterization and\ntheoretical calculation. The rate-determining step (RDS) of EOR was\nconfirmed as the oxidation process of Ni(II)–OH to Ni(III)–O\nwith one electron transfer; meanwhile, the kinetic mechanism of metal\nions doping was unveiled: (1) decreasing the oxidation potential of\nNi(II)–OH to Ni(III)–O was achieved by enhancing the\ninteraction between the adjacent Ni and O and lowering the O–H\nbond dissociation energy barrier; (2) accelerating the cycling kinetics\nof Ni(II)/Ni(III) redox by bimetallic synergy improved the electronic\ntransfer ability of materials. Our study is valuable in deeply understanding\nthe kinetic mechanism of the synergetic electrochemical-chemically\ninvolved reaction processes in NOR.