Borate intercalation optimizes the electro-oxidation kinetics of α-Ni(OH)2 nanosheets for selective electrochemical conversion of benzylamine to benzonitrile

Abstract

Selective electrochemical oxidation of amine molecules presents a promising approach for synthesizing high-value nitrile products. Nevertheless, its practical implementation is largely impeded by the challenge in activating the dehydrogenation of C(sp³)–H/N(sp³)–H bonds in amines. In this work, borate anion intercalated α-Ni(OH)₂ (BI-Ni(OH)₂) nanosheets are synthesized via a convenient microwave-assisted synthesis strategy and employed as an exceptional electrocatalyst for the benzylamine (BA) oxidation reaction (BOR). Benefiting from its better wetting behavior, larger electroactive surface area and more favorable reaction kinetics, the BI-Ni(OH)₂ catalyst shows a distinctly enhanced activity in the electro-oxidation of BA to benzonitrile (BN) compared to pristine α-Ni(OH)₂ (P-Ni(OH)₂) nanosheets, especially giving rise to a faradaic efficiency exceeding 80% toward BN production at a voltage of 1.55 V, when coupled with the cathodic hydrogen evolution reaction (HER) in a two-electrode electrolyzer. Experimental measurements and density functional theory calculations conjointly demonstrate that borate intercalation not only reduces the energy barrier for generating NiOOH species as active centers, but also promotes the adsorption of BA molecules onto the catalyst surface, enabling significantly optimized electro-oxidation kinetics for the BOR, which is accountable for the enhanced electrocatalytic performance.