Enhancing Cascade Reaction Efficiency by Local pH Regulation for Integrated Anodic H ₂ O ₂ Generation and Ammoximation

Abstract

Abstract Cascade reaction strategies integrating electrochemistry with chemical transformations offer routes for the synthesis of value‐added chemicals. However, the efficiencies of such integrated processes get compromised due to competitive electrochemical reactions and incompatibility between electrochemical and chemical transformations. We report an integrated electrochemical–chemical coupling of anodic H 2 O 2 generation with ammoximation for oxime synthesis. An FTO/Sb 2 WO 6 anode was designed and optimized to anodically produce H 2 O 2 with a maximum Faradaic efficiency (FE) of 87%. H 2 O 2 from the anode oxidizes NH 3 to NH 2 OH, which subsequently reacts with cyclohexanone to yield cyclohexanone oxime with 99% selectivity and a maximum electron efficiency (EE) of 81%. Continuous and adjustable H 2 O 2 input ensures synchronization with the ammonia oxidation reaction while minimizing over‐oxidation of the reaction intermediates. Operando scanning electrochemical microscopy (SECM) revealed local pH shifts caused by the proton‐coupled electron transfer and its effect on the FE of H 2 O 2 synthesis and competing NH 3 oxidation, providing mechanistic insights for optimizing the reaction microenvironment. By regulating the electrolyte composition to modulate the interfacial pH, side reactions were suppressed and H 2 O 2 generation was promoted, thereby enhancing cascade selectivity. This work highlights local pH regulation as a tool to improve reaction compatibility and efficiency in cascade electrosynthesis.