Efficient strategies for designing photoanodes toward selective photoelectrochemical glycerol upgrading: a review

The increasing concern for the environment and the negative impacts associated with carbonaceous compounds have driven the demand for greener and more sustainable chemical manufacturing technologies. Photoelectrochemical (PEC) technology provides an environmental and sustainable pathway for producing high value-added products by upgrading glycerol, a surplus by-product of biodiesel from biomass, while coupling with the production of high-purity hydrogen. As an emerging area, the major limiting factor in PEC glycerol oxidation is the lack of high selectivity and conversion, attributed to the parallel and sequential oxidation steps resulting from different bond cleavage positions and varying degrees of oxidation. This review aims to present a comprehensive summary of the current state of PEC glycerol oxidation from various perspectives, including product distribution, photoanode design, and oxidation mechanisms. A particular emphasis is placed on the different photoanodes used in glycerol oxidation and possible strategies for improving the activity and selectivity, including morphology and crystallization control, doping, defect engineering, metal loading, heterojunction formation, and co-catalyst deposition. Finally, we provide a comprehensive discussion of the technical challenges and future prospects for efficient PEC glycerol oxidation coupled with hydrogen production.