Selective CO2 photoreduction to CH4 mediated by dimension-matched 2D/2D Bi3NbO7/g-C3N4 S-scheme heterojunction

Discovering highly selective catalysts is key to achieve effective CO2 photoreduction to hydrocarbon fuels. In this work, we construct an ultrathin dimension-matched S-scheme Bi3NbO7/g-C3N4 heterostructure, which permits the highly selective photocatalytic reduction of CO2 to CH4, as shown by C-13 isotopic measurements. Density functional theory calculations combined with solid-state characterization confirm the electron transfer from g-C3N4 nanosheets to Bi3NbO7, establishing an internal electric field. The internal electric field drives photogenerated electrons from Bi3NbO7 to g-C3N4, as revealed by in-situ X-ray photoelectron spectroscopy, demonstrating the presence of an S-scheme charge transfer path in Bi3NbO7 to g-C3N4 heterostructures allowing efficient and selective CO2 photoreduction. As a result, the optimized sample achieved a CH4 evolution rate of 37.59 mu mol.g(-1).h(-1), a ca. 15-fold enhancement compared to ultrathin g-C3N4 nanosheets, and also retained stability after 10 reaction cycles and 40 h of simulated solar irradiation with no sacrificial reagents. The optimized Bi3NbO7 to g-C3N4 composites achieve almost 90% selectivity for CH4 production over CO. (C) 2022, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Automated summary

This study presents an ultrathin dimension-matched S-scheme Bi3NbO7/g-C3N4 heterostructure catalyst that enables highly selective photocatalytic reduction of CO2 to CH4. The presence of an internal electric field between Bi3NbO7 and g-C3N4 facilitates the transfer of photogenerated electrons, resulting in efficient and selective CO2 photoreduction.