Dual-Vacancy-Induced Selective Oxidative Cleavage of Cα–Cβ Bonds for the Electrocatalytic Depolymerization of Lignin

The electrocatalytic depolymerization of lignin into phenolic and carboxylic acid compounds presents a promising strategy for biomass valorization via selective C–C/C–O bond cleavage under mild conditions. However, two major challenges hinder its practical implementation: inefficient C–C bond cleavage and excessive overoxidation of the desired phenolic products. Herein, we demonstrate an engineered vacancy-rich nickel hydroxide catalyst (Ni(OH)2–V) that achieves exceptional performance in both Cα–Cβ bond cleavage of β-O-4 lignin linkages and suppression of phenol overoxidation. Through integrated experimental and computational analyses, this study elucidates how the synergistic introduction of cations and oxygen dual-vacancy in Ni(OH)2–V contributes to its enhanced catalytic activity. Specifically, these dual-vacancies (1) significantly enhance the interfacial adsorption of hydroxide ions on the 2-phenoxy-1-phenylethanol (2-PPE) substrate, (2) effectively lower the energy barrier of the rate-determining step (Cα–OH → Cα═O), and (3) promote the timely desorption of phenol, thereby preventing overoxidation. The optimized catalyst achieved complete conversion of 2-PPE, yielding exceptional yields of 85.7% for phenol and 96.5% for benzoic acid at 1.40 V vs the reversible hydrogen electrode (VRHE). These results represent 2.4-fold and 2.3-fold improvements over pristine Ni(OH)2. Furthermore, the practical utility of Ni(OH)2–V was validated through the depolymerization of poplar lignin and corn stover lignin, successfully yielding 14.24 and 19.54 wt % aromatic monomers. This research establishes a dual-vacancy engineering framework for precise lignin bond cleavage and offers crucial insights into the structure–activity relationship of vacancy-rich electrocatalysts for biomass valorization.