In Situ Loading of Cu Nanocrystals on CsCuCl₃ for Selective Photoreduction of CO₂ to CH₄

Rational design and facile synthesis of efficient environmentally friendly all-inorganic lead-free halide perovskite catalysts are of great significance in photocatalytic CO₂ reduction. Aiming at photogenerated charge carrier separation and CO₂ reaction dynamics, in this paper, a CsCuCl₃ /Cu nanocrystals (NCs) heterojunction catalyst is designed and synthesized via a simple acid-etching solution process by using Cu₂ O as the sacrificed template. Due to the disproportionation reaction of Cu₂ O induced by concentrated hydrochloric acid, Cu NCs can be deposited onto the surface of CsCuCl₃ microcrystals directly and tightly. As revealed by photoelectrochemical analysis, in situ Fourier transform infrared spectra, etc., the Cu NCs contribute a lot to extracting photoelectrons of CsCuCl₃ to improve the charge separation efficiency, regulating the CO₂ adsorption and activation, and also stabilizing the reaction intermediates. Therefore, CsCuCl₃ /Cu heterojunction exhibits a total electron consumption rate of 58.77 µmol g^-1 h^-1 , which is 2.9-fold of that of single CsCuCl₃ . Moreover, high CH₄ selectivity of up to 92.7% is achieved, which is much higher than that of CsCuCl₃ (50.4%) and most lead-free halide perovskite-based catalysts. This work provides an ingenious but simple strategy to rationally design cocatalysts in situ decorated perovskite catalysts for manipulating both the catalytic activity and the product selectivity.