Visible-light-driven CO2 reduction to formic acid by a rosin-derived defective TiO2/C heterostructure

The photocatalytic reduction of CO 2 into value-added chemicals is a key strategy to address the depletion of fossil fuels and foster the transition toward a circular carbon economy. Here, the synthesis under mild conditions of a defective anatase TiO 2 /carbon heterostructure, derived from a rosin-based hybrid gel, is reported. The controlled pyrolysis of rosin, a by-product of wood manufacturing, generates ordered graphitic domains interconnected with the TiO 2 matrix. This latter is enriched with oxygen vacancies that enhance light absorption and charge separation. Structural and spectroscopic analyses confirm the formation of a robust bulk heterostructure with favorable electronic properties (E g = 3.0 eV; E CB = –0.40 V vs NHE) for CO 2 photoreduction. Under both UV and visible light irradiation, and with ethanol as sacrificial donor, the catalyst yields over 3100 µg·g −1 of formic acid in 45 min, with a normalized production rate of 2.1 μmol·g −1 ·h −1 ·W −1 , outperforming several TiO 2 -based benchmark materials. Stable formic acid production with minimal formation of acetic acid is maintained across five consecutive cycles under mild conditions (pH 5). This study introduces a sustainable, low-cost photocatalyst that integrates waste valorization with efficient solar-driven CO 2 conversion, offering a scalable platform for green chemical processes.