ZnIn2S4-Catalyzed Anodic Direct Electrochemical Oxidative Cleavage of C-O Bonds in Alpha-O-4 Linkage in an Aqueous Environment

Abstract

Electrochemical selective oxidative cleavage of biomass-derived lignin feedstocks, such as C-O bond, into high-value oxygenated fine chemicals and pharmaceutical products offers an emerging route for biomass valorization. Here, we developed an efficient anodic valorization of α-O-4 lignin model compound benzyl phenyl ether (BPE) to the desirable monoaromatics products via the C-O bond direct cleavage at ZnIn2S4 anode under +1.6-2VAg/AgCl supply. A series of carbon-supported ZnIn2S4 electrodes with different hexagonal and rhombohedral phase distributions were carefully controlled and exhibited over 99% BPE conversion with specific C-O bond selectivity. We then studied substrate competition to compare the electrocatalytic performance of different ZnIn2S4 crystal phases. The experimental results were supported by density functional theory calculations. The substrate scope study revealed the suitability of the R-ZIS induced electrocatalytic system for a variety of substituted lignin α-O-4/β-O-4 model dimers. Overall, this work provides an efficient electrode and approach for enabling atom-efficient electro-refinery of diverse lignin-derived oxygenated chemicals.