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

The photocatalytic reduction of CO2 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 TiO2/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 TiO2 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 (Eg = 3.0 eV; ECB = –0.40 V vs NHE) for CO2 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 TiO2-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 CO2 conversion, offering a scalable platform for green chemical processes.