Photocatalytic reforming of lignocellulose: A review

Biomass has been considered as a promising energy resource to combat the exhaustion of fossil fuels, as it is renewable, sustainable, and clean. Photocatalytic reforming is a novel technology to utilize solar energy for upgrading biomass in relatively mild conditions. This process efficiently reforms and recasts biomass into hydrogen and/or valuable chemicals. To date, lignocellulose, including cellulose, hemicellulose and lignin, has attracted extensive studies in facile photocatalytic valorisation. This review summarizes and analyzes the most recent research advances on photoreforming of lignocellulose to provide insights for future research, with a particular emphasis on the reformation of lignin because of its 3D complex and stubborn structure. The structure of lignin contains a dominant linkage, i.e., β-O-4. The breakage of β-O-4 linkage can be proceeded by two steps, e.g., oxidization and reduction, according to the sequence of photoexcited holes and electrons. Thus, this review discusses two-step and integrate step dissociation strategies along with the rationally chosen photocatalysts. The challenges of the photocatalysts, solvent, and post-treatment were identified, and potential solutions to these challenges were provided.