A step-by-step synergistic stripping approach toward ultra-thin porous g-C3N4 nanosheets with high conduction band position for photocatalystic CO2 reduction.

The pristine g-C3N4 (BCN) with a low conversion efficiency of CO2 exits with small specific surface area, weak CO2 adsorption and severe recombination of photo-generated charges. The stripping of few-layer g-C3N4 represents excellent photocatalytic performance, which attracts extensive attention in photocatalytic CO2 reduction. In the present study, the ultra-thin porous g-C3N4 (THCN) with high specific surface area and high position of conduction band was prepared using step-by-step synergistic exfoliation. Further, we treated it with HCl-assisted hydrothermal stripping and successive thermal stripping/etching in air. Our results showed that the THCN exhibited the best CO2 conversion efficiency from CO2 to CH4 and CO fuels, compared with g-C3N4 (HCN) prepared by HCl-assisted hydrothermal stripping and g-C3N4 (TCN) prepared by thermal stripping/etching in air. Further, the excellent photocatalytic performance for CO2 reduction was mainly attributed to its high specific surface area and rich pores, excellent separation and utilization efficiency of photo-generated carriers, and upper position of conduction band. Due to its wide band gap and high specific surface area, the THCN also showed significantly better degradation for Rhodamine B than BCN, HCN and TCN. Nonetheless, using a simple two-step stripping strategy, we prepared and obtained an ultra-thin porous g-C3N4 nanosheets with a high specific surface area for CO2 conversion to CH4 and CO fuels. This ultimately provided a reference for preparation of other two-dimensional ultra-thin materials for CO2 reduction.