Moderate Active Hydrogen Generation over a NiP/CoP Heterostructure for One-Step Electrosynthesizing of Azobenzene with High Selectivity.

Through hydrogenation and N-N coupling, azobenzene can be produced via highly selective electrocatalytic nitrobenzene reduction, offering a mild, cost-effective, and sustainable industrial route. Inspired by the density functional theory calculations, the introduction of H* active NiP into CoP, which reduces the water dissociation energy barrier, optimizes H* adsorption, and moderates key intermediates' adsorption, is expected to assist its hydrogenation ability for one-step electrosynthesizing azobenzene. A self-supported NiCo@NiP/CoP nanorod array electrode was synthesized, featuring NiCo alloy nanoparticles within a NiP/CoP shell. By virtue of the thermodynamically optimal NiP/CoP heterostructure, along with overall fast electron transport in a core-shell integrated electrode, NiCo@NiP/CoP with abundant interfacial structure attains a great nitrobenzene conversion of 94.3%, especially prominent azobenzene selectivity of 97.2%, and Faradaic efficiency of 94.1% at -0.9 V (vs Hg/HgO). High-purity azobenzene crystals can also self-separate under refrigeration postelectrolysis. This work provides an energy-efficient and scalable pathway for the economical preparation of azobenzene in the electrocatalytic nitrobenzene hydrogenation.