Metal-mediated weak adsorption enables the selective electrosynthesis of N-phenylhydroxylamine from nitrobenzene hydrogenation in water

Abstract

Abstract The electrocatalytic hydrogenation of nitrobenzene (Ph-NO 2 ) to N -phenylhydroxylamine (Ph-NHOH) is of industrial importance as a high-value-added process but remains challenging because of the thermodynamically favorable overhydrogenation process. Here, metal-mediated weak adsorption is proposed to enable selective Ph-NO 2 -to-Ph-NHOH electrosynthesis in water. An activity volcano in the context of scaling relationships based on the adsorption energy of Ph-NO has identified metallic silver (Ag) as the optimal highly intrinsically active candidate for Ph-NHOH electrosynthesis. The results of in situ electrochemical infrared spectroscopy reveal the weak adsorption of Ph-NHOH on metallic Ag, which prevents its subsequent hydrogenation. Afterward, a nanosized Ag catalyst (CV-Ag) synthesized by electrodeposition is developed to rapidly and selectively synthesize Ph-NHOH under a large current. CV-Ag enhances the electrosynthesis reaction kinetics of Ph-NHOH. Therefore, an ampere-level current is realized during the electrosynthesis of Ph-NHOH, achieving a high selectivity of nearly 99.6% and continuous gram-scale synthesis of Ph-NHOH at 5.85 g per batch.