Promoting OH* adsorption by defect engineering of CuO catalysts for selective electro-oxidation of amines to nitriles coupled with hydrogen production

Developing a high-efficiency benzylamine oxidation reaction (BOR) to replace the sluggish oxygen evolution reaction (OER) is an attractive pathway to promote H2 production and concurrently realize organic conversion. However, the electrochemical BOR performance is still far from satisfactory. Herein, we present a self-supported CuO nanorod array with abundant oxygen vacancies on copper foam (Vo-rich CuO/CF) as a promising anode for selective electro-oxidation of benzylamine (BA) to benzonitrile (BN) coupled with cathodic H2 generation. In situ infrared spectroscopy demonstrates the selective conversion of BA into BN on Vo-rich CuO. Furthermore, in situ Raman spectroscopy discloses a direct electro-oxidation mechanism of BA driven by electroactive hydroxyl species (OH*) over the Vo-rich CuO catalyst. Theoretical and experimental studies verify that the presence of oxygen vacancies is more favorable for the adsorption of OH* and BA molecules, enabling accelerated kinetics for the BOR. As expected, the Vo-rich CuO/CF electrode delivers outstanding BOR activity and stability, giving a high faradaic efficiency (FE) of over 93% for BN production at a potential of 0.40 V vs. Ag/AgCl. Impressively, almost 100% FE for H2 production can be further achieved at the NiSe cathode by integrating BA oxidation in a two-electrode electrolyzer. CuO nanorod arrays with oxygen vacancies were constructed for selective electro-oxidation of benzylamine to benzonitrile coupled with H2 generation.