CoSe₂ Subnanometer Belts with Se Vacancies and Ni Substitutions for the Efficient Electrosynthesis of High-Value-Added Nitriles Coupled with Hydrogen Generation

The electrosynthesis of organic amines to high-value-added nitriles coupled with hydrogen generation is a highly efficient way to achieve carbon neutrality; however, the development of this method is greatly plagued by the lack of high-efficiency catalysts and an insufficient mechanistic understanding of electrochemical amine oxidation. Herein, a class of anion-vacancy and cation-substitution proof-of-concept atomically thin CoSe₂ subnanometer belts (SBs) are reported to greatly boost the electrooxidation of butylamine into high-value-added butyronitrile coupled with hydrogen generation. The as-fabricated CoSe₂ SBs with Se vacancies and Ni substitutions (CoSe₂/Ni−SVs SBs) exhibit an ultralow onset potential of 1.3 V with up to a ∼98.5% butyronitrile Faradaic efficiency, which surpasses all the reported Co- and Ni-based catalysts. In situ electrochemical FTIR and EIS spectroscopy studies indicate that the dramatically enhanced electrooxidation performance can be attributed to the optimized adsorption behavior and accelerated dehydrogenation kinetics. Theoretical studies further reveal that Se vacancies can act as strong Lewis acid sites to effectively strengthen the adsorption of N atoms, whereas Ni substitutions are responsible for improving the dehydrogenation thermodynamics by optimizing the sequence of dehydrogenation steps. We further demonstrate that the CoSe₂/Ni−SVs SBs are highly general and efficient catalysts for the electrosynthesis of propylamine, benzylamine, and cyclohexane methylamine into nitriles coupled with hydrogen generation. More importantly, a CoSe₂/Ni−SVs SB-based two-electrode electrolyzer that uses amine oxidation at the anode can achieve a voltage of 1.37 V at a current density of 10 mA cm⁻², which can lower the cell voltage by even 320 mV compared to that of a conventional two-electrode electrolyzer that uses the oxygen evolution reaction at the anode.