Spin-polarization and crystal structure engineering enhanced photocatalytic H2 production and photoluminescence properties in cobalt-doped CsPbBr3

In this study, the effect of Co doping in CsPbBr3 perovskite on phase transition and photocatalytic hydrogen production under a magnetic field was studied. Square CsPbBr3 nanoparticles with a dimension of 30–40 nm have been synthesized by the hot injection method. Rietveld refinement on the XRD pattern revealed the phase transition from cubic to orthorhombic after Co doping. The addition of 3%Co to CsPbBr3 resulted in a significant hydrogen production capacity of 3500 μmol/g in 4 h, with the maximum hydrogen production rate of 1042.11 μmol/g·h in the first hour, which was 1.80 times the maximum hydrogen production rate of bare CsPbBr3 (581.66 μmol/g·h). Notably, the photocatalytic H2 production of 3%Co: CsPbBr3 perovskite is significantly enhanced by applying an external magnetic field. Under the magnetic field of 2 T, the hydrogen production capacity of Co: CsPbBr3 increased to 5300 μmol/g in 4 h, with the maximum hydrogen production rate of 1828.36 μmol/g·h in the first hour, being 3.14 times the maximum hydrogen production rate of CsPbBr3 without magnetic field. The corresponding mechanism is systematically investigated by a vibrating-sample magnetometer, Electron paramagnetic resonance, UV–visible absorption, and photoluminescence spectra. The photocurrent and EIS were applied to investigate the charge-transfer kinetics of Co–CsPbBr3. The excellent photocatalytic H2 production efficiencies are because the doping of magnetic Co into highly polarized orthorhombic CsPbBr3 increased the number of spin-polarized photo-generated carriers while applying magnetic field provided spin polarization and more electron transport channels, suppressing the recombination efficiency of electrons and holes. Manipulating spin-polarized electrons in highly polarized orthorhombic photocatalytic semiconductors provides an effective strategy to boost photocatalytic H2 production efficiencies.