Selective reduction of nitrobenzene to azoxybenzene or aniline: Potential-tailored distinct terminal reconstructed active phases

Precisely controlling electroreduction of nitrobenzene (NSR) to specified products and in-depth comprehending of potential-tailored dynamic evolution of catalyst are extremely challenging. Herein, we achieved the precise control of NSR to high-value and uneasy-synthesized azoxybenzene (AOB) and clarified the potential-regulated generation of different reconstruction active phases during the NSR process, which modulates absorption behaviors of hydrogen species and organic intermediates to control selective synthesis of final products. At 0.36 V, reconstruction into Ni4N and low-content V2O5 with moderate hydrogenation ability and strengthened adsorption of nitrosobenzene and phenylhydroxylamine intermediates favors the bimolecular coupling for AOB synthesis (~100% conversion and 98.5% yield). When further negatively shifts potential to 0 V, reconstruction into metallic Ni and high-content V2O5 with strong hydrogenation ability triggers the over-reduction of nitrobenzene to aniline (AN) (~100% conversion and 99% yield). The evolved mechanism is elucidated that electrons transfer from VN to Ni3N by cathodically varying potentials. VN as an electron-donor facilitates to dissociation of H2O to produce H* and OH* species, and combines with OH* to form V2O5. Meanwhile, Ni3N as an electron-acceptor occurs the phase transformation from Ni3N to Ni4N to metallic Ni, and subsequently reacts with H* to implement selective reduction of nitrobenzene to AOB or AN.