Photocatalytic Carbon Dioxide Reduction with Water to CO and CH4 over Bio-sludge Modified TiO2 Composite

Abstract

Photocatalytic reduction of carbon dioxide (CO₂) is a promising strategy for converting greenhouse gases into valuable fuels and chemicals, contributing to sustainable energy solutions and climate change mitigation. In a continuous flow photoreactor system, this work investigates the use of waste-bio-sludge (BS) supported TiO₂ (BS/TiO₂) composite for photocatalytic reduction of CO₂ using water as the reducing agent. The bio-sludge acted as a cocatalyst, promoting efficient charge separation and transfer in addition to higher visible light absorbance. Using optimized BS/TiO₂ composite, the highest CO and CH₄ yield rates of 3.82 and 4.39 µmol g^-1 h^-1 at selectivity 46.50 and 53.50 % were achieved. When compared to pure TiO₂, the composite BS/TiO₂ was able to produce CH₄ at a higher yield rate. This was caused by the effective separation of charge carriers. This work contributes to the growing body of research on sustainable photocatalytic technologies, emphasizing the importance of designing efficient and robust photocatalysts for practical applications in CO₂ utilization and renewable energy production.