Remarkably Enhanced Hydrogen Generation of Organolead Halide Perovskites via Piezocatalysis and Photocatalysis

To alleviate photoinduced charge recombination in semiconducting nanomaterials represents an important endeavor toward high-efficiency photocatalysis. Here a judicious integration of piezoelectric and photocatalytic properties of organolead halide perovskite CH₃NH₃PbI₃ (MAPbI₃) to enable a piezophotocatalytic activity under simultaneous ultrasonication and visible light illumination for markedly enhanced photocatalytic hydrogen generation of MAPbI₃ is reported. The conduction band minimum of MAPbI₃ is higher than hydrogen generation potential (0.046 V vs normal hydrogen electrode), thereby rendering efficient hydrogen evolution. In addition, the noncentrosymmetric crystal structure of MAPbI₃ enables its piezoelectric properties. Thus, MAPbI₃ readily responds to external mechanical force, creating a built-in electric field for collective piezophotocatalysis as a result of effective separation of photogenerated charge carriers. The experimental results show that MAPbI₃ powders exhibit superior piezophotocatalytic hydrogen generation rate (23.30 µmol h⁻¹) in hydroiodic acid (HI) solution upon concurrent light and mechanical stimulations, much higher than that of piezocatalytic (i.e., 2.21 µmol h⁻¹) and photocatalytic (i.e., 3.42 µmol h⁻¹) hydrogen evolution rate as well as their sum (i.e., 5.63 µmol h⁻¹). The piezophotocatalytic strategy provides a new way to control the recombination of photoinduced charge carriers by cooperatively capitalizing on piezocatalysis and photocatalysis of organolead halide perovskites to yield highly efficient piezophotocatalysis.