Spin-Polarized Photocatalytic CO 2 Reduction of Mn-Doped Perovskite Nanoplates.

"Spin" has been recently reported as an important degree of electronic freedom to improve the performance of electrocatalysts and photocatalysts. This work demonstrates the manipulations of spin-polarized electrons in CsPbBr halide perovskite nanoplates (NPLs) to boost the photocatalytic CO reduction reaction (CORR) efficiencies by doping manganese cations (Mn) and applying an external magnetic field. Mn-doped CsPbBr (Mn-CsPbBr) NPLs exhibit an outstanding photocatalytic CORR compared to pristine CsPbBr NPLs due to creating spin-polarized electrons after Mn doping. Notably, the photocatalytic CORR of Mn-CsPbBr NPLs is significantly enhanced by applying an external magnetic field. Mn-CsPbBr NPLs exhibit 5.7 times improved performance of photocatalytic CORR under a magnetic field of 300 mT with a permanent magnet compared to pristine CsPbBr NPLs. The corresponding mechanism is systematically investigated by magnetic circular dichroism spectroscopy, ultrafast transient absorption spectroscopy, and density functional theory simulation. The origin of enhanced photocatalytic CORR efficiencies of Mn-CsPbBr NPLs is due to the increased number of spin-polarized photoexcited carriers by synergistic doping of the magnetic elements and applying a magnetic field, resulting in prolonged carrier lifetime and suppressed charge recombination. Our result shows that manipulating spin-polarized electrons in photocatalytic semiconductors provides an effective strategy to boost photocatalytic CORR efficiencies.