Regulating the Spin State of Fe III Enhances the Magnetic Effect of the Molecular Catalysis Mechanism.

Aqueous-phase oxygen evolution reaction (OER) is the bottleneck of water splitting. The formation of the O-O bond involves the generation of paramagnetic oxygen molecules from the diamagnetic hydroxides. The spin configurations might play an important role in aqueous-phase molecular electrocatalysis. However, spintronic electrocatalysis is almost an uncultivated land for the exploration of the oxygen molecular catalysis process. Herein, we present a novel magnetic Fe ^III site spin-splitting strategy, wherein the electronic structure and spin states of the Fe ^III sites are effectively induced and optimized by the Jahn-Teller effect of Cu ²⁺ . The theoretical calculations and operando attenuated total reflectance-infrared Fourier transform infrared (ATR FT-IR) reveal the facilitation for the O-O bond formation, which accelerates the production of O ₂ from OH ^- and improves the OER activity. The Cu ₁ -Ni ₆ Fe ₂ -LDH catalyst exhibits a low overpotential of 210 mV at 10 mA cm ^-2 and a low Tafel slope (33.7 mV dec ^-1 ), better than those of the initial Cu ₀ -Ni ₆ Fe ₂ -LDHs (278 mV, 101.6 mV dec ^-1 ). With the Cu ²⁺ regulation, we have realized the transformation of NiFe-LDHs from ferrimagnets to ferromagnets and showcase that the OER performance of Cu-NiFe-LDHs significantly increases compared with that of NiFe-LDHs under the effect of a magnetic field for the first time. The magnetic-field-assisted Cu ₁ -Ni ₆ Fe ₂ -LDHs provide an ultralow overpotential of 180 mV at 10 mA cm ^-2 , which is currently one of the best OER performances. The combination of the magnetic field and spin configuration provides new principles for the development of high-performance catalysts and understandings of the catalytic mechanism from the spintronic level.