Heat-Induced Magnetic Transition for Water Electrolysis on NiFeN@NiFeOOH Core–Shell Assembly

The overpotentials of electrochemical oxygen evolution reaction (OER) inherently originate from high electron transfer barriers of the redox couple driven water oxidation. Here, we propose a heat-induced magnetic transition strategy to reduce the spin-related electron transfer barriers. Coupling heat into electrochemical OER on a ferro-antiferromagnetic core–shell NiFeN@NiFeOOH, the heat-induced ferro-to-paramagnetic transition for NiFeN core at 55 °C and antiferro-to-paramagnetic transition for NiFeOOH shell at 70 °C significantly accelerate and accordingly achieve a cascaded Ni2+/Ni3+ driven water oxidation reaction. In addition, paramagnetic Niδ+ (δ ≥ 3) in NiFeN@NiFeOOH can thermochemically react with water to produce oxygen. The heat-induced magnetic transition concomitantly triggers the electrochemical redox couple driven water oxidation and the thermochemical water oxidation due to that heat-induced paramagnetic spin reduces the barriers of electricity driving the spin flipping. Our findings offer new insights into constructing the heat-electricity coupling water splitting.