In situ rapid and deep self-reconstruction of Fe-doped hydrate NiMoO4 for stable water oxidation at high current densities

The rational design of efficient electrodes that can withstand high current densities is urgent for electrolytic hydrogen generation, but it is a significant challenge to develop high activity and stability electrocatalysts with simple methods. Herein, we report an electrocatalyst that is obtained by in situ rapid depth self-reconstruction of Fe-doped hydrate NiMoO4 (denoted as NiFeMoO). Experimental and theoretical calculations show that the coleaching of crystal water and MoO42- from the original structure induces the structure crack and electrolyte penetration, as well as synergistic Fe incorporation, leading to the generation of active catalyst phase of Fe doped gamma-NiOOH (denoted as SR-NiFeMoO) during electro-oxidation. In 1 M KOH, the resulting SR-NiFeMoO, with unique poly-/low-crystalline features, possesses ultralow overpotential of 168 mV at 10 mA cm(-2) and 226 mV at 100 mA cm(-2), and performs stable catalysis for over 106 h at a high current density of 1000 mA cm(-2). In addition, the presence of dissolved Mo leads to the change of electrolyte properties over time, which leads to the continuous reduction of potential for water oxidation. The discovery of deep self-reconstruction may provide a new methodology for the development of robust and efficient electrocatalysts for electrolytic hydrogen generation.