Regulating the Spin State of Fe 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 site spin-splitting strategy, wherein the electronic structure and spin states of the Fe sites are effectively induced and optimized by the Jahn-Teller effect of Cu. 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 from OH and improves the OER activity. The Cu-NiFe-LDH catalyst exhibits a low overpotential of 210 mV at 10 mA cm and a low Tafel slope (33.7 mV dec), better than those of the initial Cu-NiFe-LDHs (278 mV, 101.6 mV dec). With the Cu 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-NiFe-LDHs provide an ultralow overpotential of 180 mV at 10 mA cm, 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.