Oxygen-bridged Schottky junction in ZnO–Ni3ZnC0.7 promotes photocatalytic reduction of CO2 to CO: Steering charge flow and modulating electron density of active sites

Developing carbon dioxide (CO 2 ) photocatalysts from transition metal carbides (TMCs) with abundant active sites, modulable electron cloud density, as well as low cost and high stability is of great significance for artificial photosynthesis. Building an efficient electron transfer channel between the photo-excitation site and the reaction-active site to extract and steer photo-induced electron flow is necessary but challenging for the highly selective conversion of CO 2 . In this study, we achieved an oxygen-bridged Schottky junction between ZnO and Ni 3 ZnC 0.7 (denoted as Zn oxide –O–Zn TMC ) through a ligand-vacancy strategy of MOF. The ZnO–Ni 3 ZnC 0.7 heterostructure integrates the photo-exciter (ZnO), high-speed electron transport channel (Zn oxide –O–Zn TMC ), and reaction-active species (Ni 3 ZnC 0.7 ), where Zn oxide –O–Zn TMC facilitates the transfer of excited electrons in ZnO to Ni 3 ZnC 0.7 . The Zn atoms in Ni 3 ZnC 0.7 serve as electron-rich active sites, regulating the CO 2 adsorption energy, promoting the transformation of *COOH to CO, and inhibiting H 2 production. The ZnO–Ni 3 ZnC 0.7 shows a high CO yield of 2674.80 μmol g –1 h –1 with a selectivity of 93.40 % and an apparent quantum yield of 18.30 % (λ = 420 nm) with triethanolamine as a sacrificial agent. The CO production rate remains at 96.40 % after 18 h. Notably, ZnO–Ni 3 ZnC 0.7 exhibits a high CO yield of 873.60 μmol g –1 h –1 with a selectivity of 90.20 % in seawater.