This thesis explores innovative strategies for enhancing the photocatalytic reduction of CO2 to clean fuels using solar energy, a critical step toward addressing global energy demands and mitigating climate change. Artificial photosynthesis, mimicking natural photosynthesis, offers a promising route to sustainable fuel production. The research focuses on synthesising and optimising semiconductors for photocatalytic CO2 reduction under sunlight.
Initial experiments used bulk g-C3N4 (BGCN) as a benchmark semiconductor. The study revealed that dispersing BGCN in anhydrous isopropanol and drop-casting onto quartz filters produced the most uniform samples. Photocatalytic CO2 reduction tests, conducted in a 20 mL reactor with H2O under 1 sun illumination, yielded CO and CH4, with optimal production rates of 0.92 µmol CO g-1 h-1 and 1.5 µmol CH4 g-1 h-1, respectively.
The research then introduced a heterojunction by combining Cs3Bi2Br9 (CBB) with BGCN. This synergy enhanced CO2 reduction efficiency, producing 14.22 µmol CO g-1 h-1, significantly higher than pure BGCN or CBB alone. Stability tests confirmed that the heterojunction remained structurally intact after 15 hours of illumination.
To further improve performance, dual modifications were applied, including surface exfoliation of BGCN and oxidation to increase surface area and charge separation. Reduced graphene oxide (rGO) was added, optimising charge recombination. The combination of rGO with exfoliated GCN (EGCN) and CBB produced even higher photocatalytic activity, yielding 25.56 µmol g-1 h-1 of mixed gases.
The research concludes with a discussion on potential charge transfer mechanisms within the composite, highlighting the heterojunction's superior photocatalytic performance and its potential as an effective CO2 reduction catalyst, contributing to advancements in solar fuel technology.