Rectifying lattice strain for selective photoelectrocatalytic conversion of lignin to aromatic acids

Abstract

The *OH-mediated oxidative C(O)‒C bond breaking is an effective approach for biomass valorization but is often hampered by inefficient/competitive adsorption of the substrate and active species. Herein, a nickel doping-enabled strain engineering strategy is presented to modulate the binding ability of interfacial sites to better reduce the kinetic barriers of the reaction process. The Ni-doped CdS photoanode with an optimal strain degree of 4.85% could realize the photoelectrochemical conversion of bio-based acetophenone to benzoic acid in an ultrahigh yield of 97.6%, outperforming the state-of-the-art catalytic systems. Mechanistic investigations corroborate that the doping of Ni species into CdS nanosheets renders the electron transfer toward Cd sites and induces lattice distortion, which can facilitate the formation of *OH (on Ni with compressible strain) and adsorption of acetophenone (on Cd with tensile strain), significantly alleviating intrinsic competitive adsorption in single sites. Moreover, the strain effect enables the moving down of d orbitals of Ni sites toward the Fermi level to promote the desorption of generated *OH for subsequent nucleophilic attack of acetophenone preactivated by Cd sites, contributing to the enhanced C(O)‒C bond cleavage to afford benzoic acid. The developed photoanode was applicable to the oxidative C–C bond cleavage of various aromatic alcohols and carbonyls containing C(O)–C motifs in lignin derivatives to benzoic acids (85%–99% yields). The two-site lattice strain engineering offers a viable route to activate both substrate and catalytic species for enhanced biomass conversion and organic transformations.