Heterogeneous photocatalytic conversion of biomass to biofuels: A review

Biofuels derived from abundant biomass are promising alternatives to fossil fuels, which are considered to be green, renewable, and sustainable. Great efforts have been made to explore efficient strategies for converting biomass to biofuels. Although thermal catalytic methods are frequently studied, but the harsh reaction conditions and high energy consumption limit their applications. Alternatively, the solar energy-driven photocatalytic approaches are considered as mild, eco-friendly and energy-saving processes, and recent achievements in the photocatalytic biomass-to-biofuels conversion significantly improve the sustainable development of biofuels. Lignocellulosic biomass and non-edible oil are seen as promising source of materials for future biofuels. In this review, photocatalytic processes for producing liquid biofuels from diverse biomass are systematically concluded, including the C-C coupling of biomass-derived platform compounds to produce diesel-like biofuels, decarboxylation reactions to produce diesel-like biofuels, and (trans)esterification of crude bio-oil to produce biodiesels. Moreover, photocatalytic conversion of biomass to produce gas biofuels is also discussed including the production of hydrogen, carbon monoxide, and syngas. The advances in photocatalysts are emphasized, and efficient photocatalysts for specific reactions and the factors influencing the catalytic performance are outlined. Moreover, perspectives for the photo-reforming of biomass to biofuels are proposed to guide further development of biofuel production.