Highly Stable CsPbBr<sub>3</sub> Nanocrystals for Photocatalytic Reduction of CO<sub>2</sub>: Ionic Liquid as a Surface Passivation Ligand and Reaction Precursor
Hao Wang, Weiwei Lu, Peng Xu, Jie Luo, Kaisheng Yao, Jun Zhang, Xuefeng Wei, Shuge Peng, Haoyan Cheng, Hao Hu, Kunpeng Sun
Abstract
All inorganic metal halide perovskites (MHPs) have been regarded as a new type of promising photocatalyst for the reduction of CO 2 . However, due to their strong ionicity and the labile surface ligands, there is still much room for improvement of the stability and efficiency of MHP photocatalysts. Here, we propose a new strategy simultaneously using ionic liquid (IL) as a surface passivation ligand and a precursor to mediate the growth and then stabilize CsPbBr 3 MHPs for the photocatalytic reduction of CO 2 . First, the TEM and XRD results show that the prepared CsPbBr 3 has a cubic morphology with the monoclinic phase when the IL of 1-octyl-3-methylimidazolium bromide ([Omim]Br) is used as the surface ligand. When the molar ratio of [Omim]Br to Pb(CH 3 COO) 2 is optimized to 2, the photoluminescence quantum yield of the prepared CsPbBr 3 can reach as high as 90.93%, suggesting the effective reduction of surface defects by the IL ligand. Importantly, the CsPbBr 3 nanocrystals show high stability under the ambient stimuli of light, heat, and humidity. The subsequent FT-IR and XPS characterizations indicate that the presence of [Omim]Br on the surface of CsPbBr 3 increases the Br-rich state, which accounts for the excellent optical property and stability of the CsPbBr 3 nanocrystals. Finally, with the assistance of IL as the activator of CO 2, the CsPbBr 3 photocatalysts provide a high evolution rate of 24.56 and 6.66 μmol g –1 h –1 for CO and CH 4, respectively. Multifunctional ILs as passivation ligands, reaction precursors, and CO 2 activators provide an efficient pathway to fabricate stable metal halide perovskites for photocatalytic CO 2 conversion.