Mechanochemical fabrication of biochar/pyrite nanocomposite for efficient photocatalytic CO₂ reduction coupled with biomass valorization

Coupling solar-driven CO₂ reduction with the valorization of waste biomass-derived platform chemicals represents a pivotal strategy toward achieving carbon neutrality and sustainable resource utilization. However, the high dissociation energy of the C=O bond in CO 2 and the complex side reactions involved in biomass conversion often result in low conversion efficiency and poor product selectivity. To address these challenges, herein, a biochar/pyrite nanocomposite was fabricated via a facile mechanical ball-milling method using natural pyrite and biochar derived from waste corn stover. During the ball-milling process, intimate interfacial contact is established between the two components, leading to the formation of a high-low heterojunction that effectively promotes the spatial separation and interfacial migration of photogenerated charge carriers. The optimized 30 wt% biochar/pyrite sample exhibits outstanding photocatalytic performance under simulated visible light irradiation, achieving a CO yield of 320.7 μmol•g -1 •h -1 with a selectivity of 90.7%, together with a 5-hydroxymethylfurfural conversion of 86.4% and a high 2,5diformylfuran selectivity of 93.2%. The incorporation of biochar not only enhances the adsorption capacity for the reactants but also substantially boosts the photocatalytic activity of pyrite through facilitated interfacial charge transfer. This work provides a new strategy for constructing efficient photocatalytic systems based on natural minerals and waste biomass, enabling the synergistic coupling of CO 2 reduction and biomass valorization.