Probing local structure and electronic structure of α-FeO/g-CN S-scheme heterojunctions for boosting CO photoreduction.

Construction of S-scheme heterojunction for photocatalytic conversion of CO into carbon-neutral fuels under 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-FeO/g-CN S-scheme heterojunctions were manufactured via an in situ self-assembly strategy for the efficient reduction of CO. The generation rate of main product CO for optimal α-FeO/g-CN heterojunction is up to 215.8 μmol g h, with selectivity of 93.3 %, which is 17.5 and 6.1 times higher than those of pristine FeO and g-CN, respectively. The local structure and electronic structure for α-FeO/g-CN heterojunction are probed by hard X-Ray Absorption Fine Structure (XAFS) and soft X-Ray Absorption Spectroscopy (XAS), as well as density-functional theory (DFT) calculations. It is found that the Fe(d)-N(p) bond formed in α-FeO/g-CN heterojunction precisely connects the conduction band (CB) of FeO and the valence band (VB) of g-CN, which minimizes the charge transfer distance and facilitates CO photoreduction activity. This work provides important information for understanding the influence of interface local and electronic structure on the performance of photo-catalytic reduction of CO at the atomic level.