Theoretical understanding of the electro-reduction of acetonitrile into ethylamine on copper: a hydride-proton stepwise mechanism

Electrochemical acetonitrile reduction reaction (ANRR) provides a promising strategy for ethylamine production and hydrogen storage. Copper based electrodes have demonstrated unique capability in electrochemical ANRR. Despite extensive exploration of ANRR, the detailed mechanism has not been clearly elucidated. Here, we give an in-depth description on the kinetics of ANRR towards ethylamine and the potential-dependent competition with hydrogen evolution reaction (HER) by using the charge extrapolation method. The activation of acetonitrile limits the activity, and the significant charge transfer in proton reduction than acetonitrile activation leads to the decreased ANRR selectivity under high overpotential. The concerted effort of surface hydride and proton is emphasized in the hydrogenation of the polar cyano group. We suggested that promoting water dissociation to supply *H and expediting acetonitrile activation via enhancing surface *H migration could be an efficient strategy in developing highly active and selective electrocatalysts for ANRR.