Modulating the local electron density at built-in interface iron single sites in Fe-CN/MoO3 heterostructure for enhanced CO2 reduction to CH4 and photo-Fenton reaction

Abstract

The catalytic efficiency of heterogeneous photocatalytic CO 2 reduction and photo-Fenton H 2 O 2 activation is closely related to the local electron density of reaction center atoms. However, electron-hole recombination from random charge transfer significantly restricts the targeted electron delivery to the active center. Herein, Fe-C 3 N 4 /MoO 3 heterojunction with interfacial coordination of atomically dispersed Fe-N 4 sites with the O interface of MoO 3 was synthesized by simple hydrothermal method. Based on the experimental results and density functional theory calculation (DFT), the heterojunction structure fosters accelerated interfacial electron transfer due to directional interfacial electric field (IEF) between Fe-CN and MoO heterogeneous interfaces, and the interfacial bond between Fe-N 4 sites and O at the built-in interface regulates the local electron density of Fe-N 4 active center. DFT further reveals that the interfacial electron flow and concentrated electron density at Fe-N 4 sites result from the coordination between Fe-N 4 and MoO 3 interfaces. This directs electron flow towards the Fe center, significantly enhancing CO 2 adsorption and H 2 O 2 conversion efficiency. PDOS analysis shows that the d yz and d z 2 orbitals of the isolated Fe atom in Fe-CN overlap with the p z orbital of the O atom in MoO 3 , playing a pivotal role in CO 2 adsorption. Consequently, the Fe-CN/MoO 3 heterojunction demonstrated highly efficient photocatalytic CO 2 reduction to CH 4 , coupled with benzyl alcohol oxidation and photo-Fenton tetracycline degradation. These findings offer a promising multifunctional catalyst strategy for the development of energy conversion and environmental remediation.