Unraveling the impact of Cu-doping in lead free halide perovskites for markedly enhancing photocatalytic CO2 reduction performance

Excessive CO2 emissions from the consumption of fossil fuels contribute to both global warming and the energy crisis. To address these pressing issues, it is essential to capture and convert CO2 into chemical feedstock using renewable energy such as solar energy. Solar-powered photocatalytic fuel production is widely acknowledged as a viable solution for a sustainable energy future. However, the development of high-performance photocatalysts remains a significant challenge to overcome in this endeavor. Recently, lead-free perovskites have emerged as a promising category of materials for CO2 photoreduction, thanks to their remarkable optoelectronic properties, cost-effective solution processing, and non-toxic nature. Nonetheless, their inherent photocatalytic CO2 reduction activity remains low due to the insufficient separation of photogenerated charges and the lack of active sites. Here, we demonstrate that Cu doping in lead-free double perovskites can lead to markedly enhanced CO2 reduction performance. The interstitial Cu dopants modulate the fermi level and introduce the active energy sites near the conduction band, which significantly enhances light absorption and separation of charge carriers. The Cu-Cs2AgBiCl6 shows the activity of 88 and 48 µmol/gcat for CH4 and CO products which are both higher than those of the pristine Cs2AgBiCl6 (27 and 10 µmol/gcat). The total yield of Cu-Cs2AgBiCl6 perovskite for CO2 photoreduction is superior to those reported under similar conditions. Transient absorption results show that hot carrier relaxation is slower and carrier decay lifetime is extended in Cu-Cs2AgBiCl6, which can enhance the charge migration efficiency and boost the CO2 reduction performance. These findings provide valuable insight into the mechanism of CO2 reduction in Cu-doped Cs2AgBiCl6 perovskite crystals and suggest that Cu-doping is a promising strategy for developing highly efficient and selective CO2 reduction photocatalysts.