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. (C) 2021 Elsevier Inc. All rights reserved.

Automated summary

The ultra-thin porous g-C3N4 (THCN) demonstrated superior photocatalytic performance for CO2 reduction due to its high specific surface area, rich pores, efficient separation and utilization of carriers, and upper position of conduction band. The high specific surface area and unique structure of THCN also resulted in significantly better degradation of Rhodamine B compared to other materials. This study provides a reference for preparation of other two-dimensional ultra-thin materials for CO2 reduction.