The photo-decomposition and self-restructuring dynamic equilibrium mechanism of Cu2(OH)2CO3 for stable photocatalytic CO2 reduction

Developing suitable photocatalysts and understanding their intrinsic catalytic mechanism remain key challenges in the pursuit of highly active, good selective, and long-term stable photocatalytic CO2 reduction (PCO2R) systems. Herein, monoclinic Cu2(OH)2CO3 is firstly proven to be a new class of photocatalyst, which has excellent catalytic stability and selectivity for PCO2R in the absence of any sacrificial agent and cocatalysts. Based on a Cu2(OH)213CO3 photocatalyst and 13CO2 two-sided 13C isotopic tracer strategy, and combined with in situ diffused reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis and density functional theory (DFT) calculations, two main CO2 transformation routes, and the photo-decomposition and self-restructuring dynamic equilibrium mechanism of Cu2(OH)2CO3 are definitely revealed. The PCO2R activity of Cu2(OH)2CO3 is comparable to some of state-of-the-art novel photocatalysts. Significantly, the PCO2R properties can be further greatly enhanced by simply combining Cu2(OH)2CO3 with typical TiO2 to construct composites photocatalyst. The highest CO and CH4 production rates by 7.5 wt% Cu2(OH)2CO3-TiO2 reach 16.4 μmol g−1 h−1 and 116.0 μmol g−1 h−1, respectively, which are even higher than that of some of PCO2R systems containing sacrificial agents or precious metals modified photocatalysts. This work provides a better understanding for the PCO2R mechanism at the atomic levels, and also indicates that basic carbonate photocatalysts have broad application potential in the future.