Highly Selective Photoelectrochemical Glycerol Valorization toward Lactic Acid with Low-Valence Bimetallic Overlayer on CuWO4

Selective glycerol valorization to lactic acid is a promising approach for upgrading biomass-derived waste into value-added chemicals. Herein, we demonstrate photoelectrochemical lactic acid production via glycerol oxidation using a surface-reconstructed n-type CuWO₄ photoanode (R-CuWO₄). The R-CuWO₄ exhibits a solution selectivity of 95.9%, a yield rate of 159.8 mmol m^–2 h^–1, and a Faraday efficiency of 59.5%. The reconstructed surface overlayer improves catalytic kinetics, reducing the overpotential and increasing the glycerol conversion rate. Additionally, the presence of low-valence copper in the overlayer tailors the reaction pathway, favoring lactic acid formation. Density functional theory calculations reveal that this effect is associated with a change in the glycerol adsorption configuration from terminal to middle hydroxyl groups on the reduced Cu sites in R-CuWO₄. Our findings suggest that surface engineering through electrochemical treatment can control the adsorption behavior and guide product selectivity in photoelectrochemical biomass conversion.