Bandgap engineered g-C3N4 and its graphene composites for stable photoreduction of CO2 to methanol

• Published in: Carbon (New York) 2022-06, Vol.192, p.101-108
• Main Authors: Sahoo, Ramesh Chandra, Lu, Haijiao, Garg, Dimple, Yin, Zongyou, Matte, H.S.S. Ramakrishna
• Format: Article
• Language: English
• Subjects: Carbon nitrides; CO2 reduction; Copolymerization; Hydrogen evolution; Methanol; Photocatalysis
• ISSN: 0008-6223; 1873-3891
• DOI: 10.1016/j.carbon.2022.02.021

Carbon nitride (g-C3N4) is a two-dimensional material with several advantages over other photocatalysts, such as metal-free, biocompatible, chemically and thermally stable, to name a few. However, it usually suffers from low charge carrier mobility, high recombination rate, low electrical conductivity, and, more importantly, low absorption in the visible range. To address the multiple shortcomings, a simple and cost-effective copolymerization strategy was developed to synthesize g-C3N4 by selecting the appropriate precursors and optimizing the synthesis parameters, which resulted in lowering the bandgap from 2.80 eV to as narrow as 2.40 eV. To further improve the charge separation and conductivity, g-C3N4 and reduced graphene oxide (rGO) based composites were synthesized. The obtained composite catalysts were studied for photocatalytic CO2 reduction. It is important to note that g-C3N4/rGO composites resulted in the selective photoreduction of CO2 to methanol as the only liquid product with evolution rates of ∼114 μmol g−1 h−1 along with H2 (68 μmol g−1 h−1) under scavenger free conditions and exhibited robust stability. [Display omitted]