In situ topotactic formation of an inorganic intergrowth bulk NiS/FeS@MgFe-LDH heterojunction to simulate CODH for the photocatalytic reduction of CO2.

Abstract

Enzyme-mimetic photocatalysis has been attracting much attention in bionic research, in which carbon monoxide dehydrogenase (CODH) is a suitable prototype for simulation to meet environmental and energy needs. In this study, we utilized the structural memory effect of layered double hydroxides (LDHs) to build inorganic intergrowth bulk heterojunctions (IIBHs) NiS/FeS@MgFe-LDHs via a pyrolytic topological vulcanization (PTV) method that imitated active C-clusters [Ni-4Fe-4S] in CODH. Enzyme mimicry was evaluated in terms of the microstructure and catalytic reaction site. The similarity between the microstructure of NiS/FeS@MgFe-LDHs and the CODH active group was demonstrated through XRD, XAFS and other characterisations. Subsequently, the obtained in situ irradiated X-ray photoelectron spectra and transient absorption spectra indicated the photogenerated electron transfer of the IIBH, wherein electrons finally accumulated in the conduction band of the NiS domain for the photocatalytic CO2 reduction reaction, which was similar to that of C-clusters [Ni-4Fe-4S] in which the Ni2+ ion was the reactive site. As a result, NiS/FeS@MgFe-LDHs achieved a high yield of CO at a rate of 2151.974 μmol g-1 h-1, which was 39.8 and 9.7 times more than that of NiMgFe-LDHs and NiMgFe-MMO, respectively. The study offers an innovative design route for developing IIBHs, providing novel opportunities for enzyme-mimetic photocatalysis.