Energy-efficient hydrogen production over a high-performance bifunctional NiMo-based nanorods electrode

Electrochemical water splitting to hydrogen fuel is highly desirable yet challenging mainly limited by sluggish cathodic oxygen evolution reaction (OER). Urea electrolysis can produce hydrogen more energy-savingly by replacing OER process with urea oxidation reaction (UOR) due to favorable thermodynamic potential, however lacking efficient UOR catalysts restricts the industrial application. Here we reported novel NiMo-based nanorods, Ni/Ni_0.2Mo_0.8N/MoO₃, by thermal ammonolysis of NiMo-based precursor as excellent catalyst for OER and hydrogen evolution reaction (HER) with small overpotentials of 252 mV, and 103 mV to achieve a current density of 10 mA cm^-2 in 1.0 M KOH. Moreover, the Ni/Ni_0.2Mo_0.8N/MoO₃ shows fabulous catalytic UOR activity with a low potential of 1.349 V at 10 mA cm^-2, outperforming most recently reported non-noble metal catalysts and commercial RuO₂. More importantly, the cell voltage of urea electrolysis using Ni/Ni_0.2Mo_0.8N/MoO₃ as cathode for HER and anode for UOR is significantly reduced from 1.52 V of traditional water electrolysis to 1.356 V to deliver 10 mA cm^-2 with excellent stability for over 400 h, superior to almost recently reported catalysts. The high performances result from the synergistic effect between highly active and conductive metal nickel and nitride, and nanorods arrays grown on 3D substrate. This work demonstrates that this material holds encouraging potential in large-scale energy-saving H₂ production and urea-related wastewater treatment.