Upcycling CO2 to Formic Acid Using Biomass-Derived BiOBr Photocatalysts

Abstract

The use of photocatalytic for the management of excess biogas in power plants in palm oil mills is a promising technology to convert CO2 into value-added chemicals. This technology also supports energy sustainability and reduces greenhouse gas emissions. This study synthesized a BiOBr-based photocatalyst combining it with commercial activated carbon and activated carbon from biomass obtained from empty fruit bunches (EFB). Structural characterization confirmed the formation of a tetragonal BiOBr phase, while UV-Vis DRS analysis showed a narrowing of the optical band gap from 2.88 eV (BiOBr) to 2.32 eV (BiOBr-ACT), which was caused by the presence of oxygen vacancies and carbon-induced mid-gap states. BET analysis revealed that the BiOBr-ACT composite exhibited the most substantial specific surface area (27.7437 m2/g) and a finer mesoporous structure. These characteristics of the photocatalyst are crucial in enhancing CO2 absorption and light utilization. When exposed to UV-visible light, BiOBr-ACT showed a significant increase in formic acid productivity (3.6470 mmol gcat−1 h−1) compared to pure BiOBr (0.4190 mmol gcat−1 h−1). This superior performance of BiOBr-ACT demonstrated the synergistic effect of the porous structure and the band gap engineering of the photocatalyst, thus demonstrating the potential of biomass-derived activated carbon as an effective support for developing efficient and sustainable photocatalysts for CO2 reduction.