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

Abstract

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 13C 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/g-C3N4 heterostructures allowing efficient and selective CO2 photoreduction. As a result, the optimized sample achieved a CH4 evolution rate of 37.59 μmol·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/g-C3N4 composites achieve almost 90% selectivity for CH4 production over CO.