Spin Magnetic Effect Activate Dual Site Intramolecular O─O Bridging for Nickel-Iron Hydroxide Enhanced Oxygen...

The oxygen evolution reaction (OER) involves the recombination of diamagnetic hydroxyl (OH) or water (H₂O) into the paramagnetic triplet state of oxygen (O₂). The spin conservation of oxygen intermediates plays a crucial role in OER, however, research on spin dynamics during the catalytic process remains in its early stages. Herein, β-Ni(OH)₂ and Fe-doped β-Ni(OH)₂ (Ni₅Fe₁(OH)₂) are utilized as model catalysts to understand the mechanism of spin magnetic effects at iron (III) sites during OER. Combined with magnetic characterization, it is founded that the introduction of Fe transforms the antiferromagnetic Ni(OH)₂ into a ferromagnetic material. Testing the magnetic response of the catalyst under an external magnetic field, the OER activity of Ni₅Fe₁(OH)₂ is significantly enhanced in comparison to Ni(OH)₂. This improvement is likely due to the introduction of iron sites, which promote spin magnetic effects and enhance reaction kinetics, thereby increasing catalytic efficiency. Combining experimental and theoretical characterization, it is discovered that the iron sites accelerate the formation of heterogeneous dual-site O─O bridging, represented as ─Ni─O─O─Fe─, thereby effectively enhancing the kinetics of the OER reaction. This study provides a magnetic perspective on the structure-function relationship of magnetic iron-based catalysts and has significant implications for the design of new catalysts.