Coupling Joule Heating with Vibration Ball Milling\nfor Synthesizing Carbon-Supported Ni<sub>100–<i>x</i></sub>Fe<sub><i>x</i></sub> Nanoparticles Achieving Efficient\nOxygen Evolution and Alkaline Wate

Rapid\nand cost-effective synthesis of electrocatalysts for oxygen\nevolution reaction (OER) poses a significant technical challenge for\nthe commercialization of water electrolysis. We, herein, report a\nfacile strategy that couples quick Joule heating with mechanical ball\nmilling for synthesizing well-defined Ni<sub>100–<i>x</i></sub>Fe<sub><i>x</i></sub> (0 ≤ <i>x</i> ≤ 100) alloy nanoparticles on carbon substrate toward high-efficiency\nOER and water splitting. This synthetic strategy involves first simply\nmixing the precursors and carbon substrate through ball milling and\nsubsequent Joule heating on an electrical device for fast forming\ncarbon-supported alloy nanoparticles with fine sizes and uniform distribution.\nIn particular, the single-component Ni/C nanoparticles (i.e., <i>x</i> = 0) synthesized by this way include both fcc and hcp\ncrystal phases, with the highest proportion of hcp phase at 370 °C,\nwhich endows the Ni/C nanoparticles with better OER activity than\nthat of Ni/C samples synthesized at other temperatures. In addition,\nthe Ni<sub>100–<i>x</i></sub>Fe<sub><i>x</i></sub>/C nanoparticles at an appropriate Ni/Fe ratio of 72/28 (Ni<sub>72</sub>Fe<sub>28</sub>/C) exhibit the best OER electrocatalysis,\nwith a low overpotential of only 276 mV at a current density of 10\nmA cm<sup>–2</sup>, due to the optimal electronic interaction\nbetween Ni and Fe in the alloys. More importantly, under simulated\nindustrial electrolysis conditions (30 wt % KOH at 60 °C), a\ntwo-electrode alkaline electrolyzer assembled with Ni<sub>72</sub>Fe<sub>28</sub>/C at the anode and commercial Pt/C at the cathode\n(Ni<sub>72</sub>Fe<sub>28</sub>/C||Pt/C) requires only 1.39 V to deliver\nthe current density of 100 mA cm<sup>–2</sup>, along with an\nexcellent 120-h durability at the same current density.