One-step synthesis of amorphous nickel iron phosphide hierarchical nanostructures for water electrolysis with superb stability at high current density.

The development of noble-metal-free high-performance bifunctional catalysts for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is essential but challenging for hydrogen production from water electrolysis. Herein, amorphous bimetallic nickel-iron phosphide hierarchical nanostructures enrooted on nickel-iron alloy foam (NiFeP/NFF) are facilely fabricated via direct phosphidation of NFF at low temperature and developed as an efficient self-supporting bifunctional electrocatalyst to catalyze both the OER and HER with high activity, fast kinetics and excellent stability. Moreover, an alkaline water electrolyzer simultaneously utilizing NiFeP/NFF as the cathode and anode only needs a cell voltage of 1.58 V to afford a current density of 10 mA cm-2, overpassing most of the reported bifunctional electrocatalysts and comparable to noble metal-based ones. Impressively, the NiFeP/NFF-based symmetric electrolyzer can work well without appreciable performance degradation at a high current density of 500 mA cm-2 for over 1000 h for continuous hydrogen production with 100% faradaic efficiency, showing superb durability and great promise for industrial application.