Regulating the Spin State of Fe<sup>III</sup> Enhances the Magnetic Effect of the Molecular Catalysis Mechanism
Zemin Sun, Liu Lin, Jinlu He, Dajie Ding, Tongyue Wang, Jie Li, Mingxuan Li, Yicheng Liu, Yayin Li, Mengwei Yuan, Binbin Huang, Huifeng Li, Genban Sun
Abstract
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 FeIII site spin-splitting strategy, wherein the electronic structure and spin states of the FeIII sites are effectively induced and optimized by the Jahn–Teller effect of Cu2+. 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 O2 from OH– and improves the OER activity. The Cu1–Ni6Fe2–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 Cu0–Ni6Fe2–LDHs (278 mV, 101.6 mV dec–1). With the Cu2+ 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 Cu1–Ni6Fe2–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.