Construction of 2D/2D S-scheme Pg-C₃N₄/Fe₂TiO₅ nanosheets with enhanced photogenerated charge separation for highly selective photoconversion of CO₂ into fuels

A template-free synthesis method has been developed to fabricate two-dimensional (2D) protonated g-C₃N₄ (Pg-C₃N₄) nanosheets coupled with 2D Fe₂TiO₅ nanosheets, forming robust 2D/2D heterostructures. These heterojunctions leverage strong electrostatic interactions between the positively charged Pg-C₃N₄ and negatively charged Fe₂TiO₅, facilitating efficient charge separation via an S-scheme mechanism. This unique charge transfer pathway significantly enhances the utilization of photoinduced carriers, leading to superior photocatalytic performance in CO₂ conversion with H₂O. The Pg-C₃N₄/Fe₂TiO₅ heterostructure exhibited remarkable activity, achieving CH₃OH and dimethyl ether (DME) production rates of 247.6 and 100.5 µmol/g-cat, respectively. Additionally, a quantum yield of 0.85 % for CH₃OH formation was recorded, which is 3.1 and 1.7 times higher than the yields of standalone Pg-C₃N₄ and Fe₂TiO₅ photocatalysts, respectively. The enhanced photocatalytic activity is attributed to the optimized charge transfer dynamics enabled by the S-scheme heterojunction. This study offers valuable insights into the design of template-free heterostructures for efficient photocatalytic CO₂ conversion and other solar-driven processes.