Spontaneous‐Spin‐Polarized 2D π‐d Conjugated Frameworks Towards Enhanced Oxygen Evolution Kinetics

Abstract Alternative strategies to design sustainable‐element‐based electrocatalysts enhancing oxygen evolution reaction (OER) kinetics are demanded to develop affordable yet high‐performance water‐electrolyzers for green hydrogen production. Here, it is demonstrated that the spontaneous‐spin‐polarized 2D π‐d conjugated framework comprising abundant elements of nickel and iron with a ratio of Ni:Fe = 1:4 with benzenehexathiol linker (BHT) can improve OER kinetics by its unique electronic property. Among the bimetallic NiFe _x:y ‐BHTs with various ratios with Ni:Fe = x:y, the NiFe _1:4 ‐BHT exhibits the highest OER activity. The NiFe _1:4 ‐BHT shows a specific current density of 140 A g ⁻¹ at the overpotential of 350 mV. This performance is one of the best activities among state‐of‐the‐art non‐precious OER electrocatalysts and even comparable to that of the platinum‐group‐metals of RuO ₂ and IrO ₂ . The density functional theory calculations uncover that introducing Ni into the homometallic Fe‐BHT (e.g., Ni:Fe = 0:1) can emerge a spontaneous‐spin‐polarized state. Thus, this material can achieve improved OER kinetics with spin‐polarization which previously required external magnetic fields. This work shows that a rational design of 2D π‐d conjugated frameworks can be a powerful strategy to synthesize promising electrocatalysts with abundant elements for a wide spectrum of next‐generation energy devices.