Photoelectrochemical oxidation for biomass valorization: Upgrading biorefinery-derived feedstocks into value-added chemicals.

Photoelectrochemical (PEC) oxidation has emerged as a transformative platform for sustainable biomass valorization, enabling direct solar-to-chemical conversion under mild conditions with enhanced selectivity toward value-added products. Compared with conventional thermochemical routes that suffer from high energy consumption and poor product selectivity, PEC systems integrate photogenerated charge separation with electrocatalytic transformations, thereby improving energy efficiency and enabling precise control over oxidation pathways. This review systematically summarizes recent advances in PEC technologies for biomass upcycling, with particular emphasis on diverse substrate categories including polyols (glycerol), monohydric alcohols (methanol and benzyl alcohol), furanic compounds (HMF and furfural), as well as complex biomass feedstocks such as carbohydrates, organic acids, and lignin derivatives. For each substrate class, we highlight how photoanode engineering strategies-such as heterojunction construction, cocatalyst integration, defect regulation, and interfacial microenvironment control-govern charge transfer pathways, reaction intermediates, and product distributions. In addition, key challenges for practical deployment are critically discussed, including the use of real feedstock streams, catalyst stability against fouling and corrosion, reactor-scale mass transfer, and downstream product separation. Finally, emerging opportunities in reactor engineering, paired redox configurations, and data-driven catalyst discovery are outlined to guide future development of scalable PEC biomass upgrading technologies.