Accelerated charge transfer of g-C3N4/BiVO4 Z-scheme 2D heterojunctions by controllably introducing phosphate bridges and Ag nanocluster co-catalysts for selective CO2 photoreduction to CO

Artificial Z-scheme heterojunctions by mimicking photosynthesis have been widely investigated for photoreduction of CO2, yet the activity is hindered by the weak interfacial interactions and insufficient CO2 activation sites. Here, a cascade Z-scheme g-C3N4/BiVO4 (CN/BVO) heterojunction has been tailored by the dual modification of phosphates and Ag nanoclusters for CO2 reduction in pure water, in which phosphates are modified in the interface of CN/BVO by a facile impregnation method, while Ag nanoclusters are anchored on the surface of CN by a light induced in-situ deposition strategy under a low-temperature environment created by liquid N2. The optimal Ag-CN/PO-BVO heterojunction delivers a 48 μmol g-1 h-1 CO conversion rate with 97% selectivity, which exhibits a 24-fold increment in CO production rate compared with that of pristine BVO. The improved photoactivity is mainly ascribed to the accelerated Z-scheme charge transfer from the built PO-bridged dimension-matched 2D interfaces and from the introduced Ag nanoclusters with preferable catalytic functions for CO2 reduction mainly by means of the time-resolved surface photovoltage responses and fluorescence spectra. Moreover, temperature-programmed desorption curves and in-situ DRIFTS results demonstrate that the introduced Ag is favorable for CO2 activation and CO desorption with COOH intermediates, responsible for the high CO selectivity.