Unveiling the Crucial Role of Oxygen Evolution Reaction for Boosting the Electroxidative C-C Bond Cleavage in Biomass Valorization

Abstract

The electrocatalytic oxidative cleavage of the C–C bond is highly effective for converting biomass lignin into high-value-added aromatic chemicals. However, the oxygen evolution reaction (OER) at the applied oxidative potential usually competes in the aqueous environment. Despite this challenge, this study found that OER does not entirely hinder the cleavage process but rather acts as a synergistic catalytic step. By using defect-rich carbon nanotubes as the electrocatalyst and combining experimental and theoretical analysis, we found that the reactive oxygen species (O2−) formed before *O2 desorption (the rate-determining step in OER) serve as the key oxygen source. These species could interact with the enolate intermediate of lignin, which facilitates the in situ production of aromatic compounds. Under the optimal potential of 0.5 V vs. Ag/AgCl, 98.8% of 2-phenoxyacetophenone is converted into phenol and benzoic acid via Cα–Cβ bond cleavage, with yields of 62.31% and 43.42%, respectively. Additionally, the depolymerization of quasi-natural poplar lignin achieves a total monomer yield of up to 12.41 wt%. This study provides new mechanistic insights into Cα–Cβ bond cleavage during electrocatalytic lignin depolymerization under alkaline conditions, contributing to efficient biomass valorization.