Dual-vacancy-induced interfacial electron transfer in a g-C3N4/BiOCl heterojunction for efficient photocatalytic CO2 reduction to CO.

Photocatalytic CO2 reduction offers an attractive strategy for producing solar fuels, but however, its performance remains constrained by insufficient CO2 capture and activation, together with inefficient electron migration across the heterointerface. Herein, we construct an N-vacancy-rich g-C3N4/O-vacancy-rich BiOCl heterojunction (VN-CN/VO-BOC) with complementary dual-vacancy sites. Compared with isolated vacancies, the dual-vacancy VN-CN/VO-BOC heterojunction induces asymmetric interfacial charge redistribution and electron accumulation, creating favorable active sites for enhanced CO2 adsorption and thus promoting CO bond activation. As a result, VN-CN/VO-BOC achieves a CO yield of 8.5 μmol g-1 h-1 with nearly 100% CO selectivity, which is 2.7 and 7.4 times higher than those of VO-BOC and VN-CN, respectively. In situ DRIFTS and DFT (density functional theory) calculations further reveal that the double vacancy interface (VN-interface-VO) could effectively promote the adsorption and activation of CO2. Transient absorption spectroscopy further confirms accelerated interfacial charge transfer and prolonged carrier lifetimes. This work provides an effective dual-vacancy interface strategy for highly selective photocatalytic CO2 reduction.