Tailoring Cu ⁺ /Cu ⁰ Ratios of Copper-Based Electrocatalysts for Benzonitrile-to-Benzylamine Transformation

Catalytic electroreduction of benzonitrile offers a promising sustainable alternative to thermocatalytic approaches for benzylamine synthesis under mild conditions. Inspired by a decoupling strategy, herein, we rationally constructed dual-active sites of Cu⁺ and Cu⁰ within Cu₂O/Cu nanowire array (Cu₂O/Cu-NA) electrocatalysts for water and benzonitrile activation, respectively. This design enabled exceptional catalytic performance for benzonitrile-to-benzylamine electroreduction. Precise control of the electroreduction potentials of CuO nanowire array for the synthesis of Cu₂O/Cu-NA allowed the modulation of Cu⁺/Cu⁰ ratios. A volcano-shaped correlation was observed between the electrocatalytic activity of Cu₂O/Cu-NA and Cu⁺/Cu⁰ ratios. Experimentally, the Cu₂O/Cu-NA with a Cu⁺/Cu⁰ ratio of 0.98 delivered the optimal catalytic performance with a benzonitrile conversion of 99.8%, a benzylamine selectivity of 98.7% and a Faradaic efficiency of 98.8% at -0.37 V vs. RHE. Comprehensive mechanistic investigations demonstrate the distinct roles of Cu⁺ in generating *H through water activation and Cu⁰ in activating/reducing benzonitrile. The intimate Cu₂O/Cu interface facilitates kinetic matching between the *H generation and nitrile reduction, leading to selective benzonitrile-to-benzylamine transformation and suppressing side reactions and the competing hydrogen evolution reaction.