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 3 halide perovskite nanoplates (NPLs) to boost the photocatalytic CO 2 reduction reaction (CO 2 RR) efficiencies by doping manganese cations (Mn 2+ ) and applying an external magnetic field. Mn-doped CsPbBr 3 (Mn-CsPbBr 3 ) NPLs exhibit an outstanding photocatalytic CO 2 RR compared to pristine CsPbBr 3 NPLs due to creating spin-polarized electrons after Mn doping. Notably, the photocatalytic CO 2 RR of Mn-CsPbBr 3 NPLs is significantly enhanced by applying an external magnetic field. Mn-CsPbBr 3 NPLs exhibit 5.7 times improved performance of photocatalytic CO 2 RR under a magnetic field of 300 mT with a permanent magnet compared to pristine CsPbBr 3 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 CO 2 RR efficiencies of Mn-CsPbBr 3 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 CO 2 RR efficiencies.