Probing Local Structure and Electronic Structure of Α-Fe2o3/G-C3n4 S-Scheme Heterojunctions for Boosting Co2 Photoreduction

Abstract

Construction of S-scheme heterojunction photocatalytic system for conversion of CO2 and pure H2O into carbon-neutral fuels using sunlight is of paramount value for the sustainable development of energy. However, few reports are concerned the local structure and electronic structure of semiconductor heterojunction, which are importance of understanding the effect of heterojunction structure on the photocatalytic property. In this work, hierarchical α-Fe2O3/g-C3N4 S-scheme heterojunctions were manufactured via an in situ self-assembly strategy for the efficient reduction of CO2. The generation rate of main product CO for optimal α-Fe2O3/g-C3N4 heterojuction is up to 215.8 μmol g-1 h-1, with selectivity of 93.3%, which is 17.5 and 6.1 times higher than those of pristine Fe2O3 and g-C3N4, respectively. The local structure and electronic structure for α-Fe2O3/g-C3N4 heterojunction are probed by hard X-Ray Absorption Fine Structure (XAFS) and soft X-Ray Absorption Spectroscopy (XAS), as well as DFT calculations. It is found that the Fe(d)-N(p) bond formed in α-Fe2O3/g-C3N4 heterojunction precisely connects the conduction band (CB) of Fe2O3 and the valence band (VB) of g-C3N4, which minimizes the charge transfer distance and facilitates CO2 photoreduction activity. This work supplies deeper comprehension of the relationship between photocatalytic activity and local structure, as well as electronic structure, precisely regulating S-scheme charge transfer and profoundly revealing the mechanism of CO2 photoreduction.

Keywords: α-Fe2O3/g-C3N4, Local structure, S-scheme, interface, CO2 photoreduction