Photothermal Synergistic Catalysis of Cellulose Liquefaction by BiOCl‐g‐C ₃ N ₅ Heterojunction Photocatalysts: Enhanced Bio‐Oil Yield and Quality

With increasing attention to fossil fuel consumption and environmental pollution, the development of clean and sustainable biofuels has become increasingly urgent. Hydrothermal liquefaction (HTL) is a promising technology for converting biomass into bio-oil, but traditional HTL processes face challenges such as low conversion efficiency and high energy consumption. To address these issues, this study synthesized a series of B/CN heterogeneous photocatalysts with different BiOCl (BOC) and g-C₃N₅ molar ratios by solvothermal method and applied them to the photothermal synergistic catalytic liquefaction of cellulose in methanol. Methanol can be recycled and reused. It has been proven that BOC formed a heterojunction with g-C₃N₅, extending the photo responsive range of the photocatalyst to the visible light region, promoting the separation and transfer of photogenerated carriers, and optimizing the dispersion of active components. The effect of photocatalyst on the chemical composition and thermal stability of bio-oil was studied. The B/CN-1:2 photocatalyst achieved optimal performance, with a maximum yield of 61.23 • wt% for bio-oil, an higher heating value of 21.39 MJ/kg, and an energy conversion efficiency of 77.41%. Bio-oil is mainly composed of high-value compounds such as alcohols, esters, and ethers, with reduced heavy components and improved thermal stability. Mechanistic studies have shown that the photothermal synergistic effect of B/CN catalysts promotes the cleavage of cellulose glycosidic bonds by generating reactive free radicals through the photodegradation of methanol. This work provides a feasible strategy for improving the efficiency and quality of biomass HTL by designing high-performance photothermal catalysts and offers new insights for the sustainable production of biofuels.