Efficient Photoelectrocatalysis of Glycerol to Dihydroxyacetone and Synergistic Hydrogen Generation via Dual Oxidation Pathways Using Co-LDH/Bi₂O₃/TiO₂ Ternary Array

Replacing the oxygen evolution reaction (OER) in photoelectrocatalytic (PEC) water splitting with glycerol oxidation reaction (GOR) not only enhances hydrogen production but also generates high-value glycerol byproducts. In this study, we developed a ternary photoanode, Co-LDH/Bi₂O₃/TiO₂, by loading particulate Bi₂O₃ and linear Co-LDH onto a TiO₂ nanorod for glycerol conversion and hydrogen production. The characterization results confirm the formation of coupled interfaces between Co-LDH and Bi₂O₃ and TiO₂, which improves the visible light utilization and promotes the formation of type II heterojunctions, resulting in a significant suppression of electron–hole recombination and an improvement in the PEC performance. Fourier transform infrared (FT-IR) spectroscopy revealed that the Co-LDH/Bi₂O₃/TiO₂ photoanode exhibited stronger adsorption of glycerol intermediate hydroxyl group and more effective desorption of DHA compared to TiO₂ and binary photoanodes (Co-LDH/TiO₂ and Bi₂O₃/TiO₂), resulting in high-selectivity glycerol conversion to DHA. Mechanistic studies and density function theory calculations have shown that the binary photoanode Co-LDH/TiO₂ oxidizes glycerol mainly through hole oxidation, and the binary photoanode Bi₂O₃/TiO₂ oxidizes glycerol mainly through hydroxyl radical (^•OH) oxidation. Therefore, the ternary photoanode constructed (Co-LDH/Bi₂O₃/TiO₂) with a dual heterojunction converts glycerol through the dual pathways of hole oxidation and ^•OH oxidation. This work demonstrates a promising strategy for developing high-performance photoanodes in PEC systems for glycerol oxidation and hydrogen production, leveraging the synergistic effects of multisemiconductor heterojunctions and multiple oxidation pathways, offering significant potential for practical applications.