Nitrogen doped carbon encapsulated hierarchical NiMoN as highly active and durable HER electrode for repeated ON/OFF water electrolysis

Water electrolysis powered by tidal, wind and solar energies is an ideal green hydrogen production path. However, intermittent power supply and unpredictable power cut by renewable energy resources inevitably compel the electrode materials to suffer from the fluctuant working conditions or repeated start/stop operation, which always leads the deterioration of electrocatalyst. Herein, a novel hydrogen evolution reaction (HER) electrode with hierarchical NiMoN microrod arrays encapsulated by nitrogen doped ultra-thin carbon layer and in-situ grown on nickel foam (labelled NF) was reported. The prepared NiMoN@NC/NF electrode exhibits extremely low overpotentials less than 10 mV at 10 mA cm-2 for HER in both KOH and H2SO4 electrolytes. Importantly, it exhibits not only high stability during the 100 h repeated ON/OFF test, but also high oxidation resistance and corrosion resistance in acid electrolyte. The water electrolysis cell, using 100 cm2 NiMoN@NC/NF cathode and NiFe based anode, supplies a high current density of 100 mA cm-2 with a low cell voltage of 1.53 V at 88 degrees C. The appropriate nitrogen doping, carbon encapsulation, and the well-designed hierarchical structure of the NiMoN@NC/NF endow its optimized Gibbs free energy of H*, excellent activity and outstanding adaptability to harsh conditions, demonstrating its great prospect in the repeated ON/OFF electrolysis associated with changeful renewable electricity.