Periodic Corrosion Turns Bulk Ni into Zr-Incorporated Polycrystalline Ni(OH)₂ Nanoarrays for Overall Water Decomposition

To promote the scaled-up production efficiency of low-cost electrocatalysts, a periodic oxygen-assisted corrosion method was proposed to turn bulk Ni foam into Zr-incorporated polycrystalline Ni(OH)2 nanosheets (Zr-Ni(OH)2) at room temperature. The uniform nanoarray morphology was formed in situ on the surface through natural oxygen uptake corrosion in air within 40 min. The Zr element induced rich lattice distortion and changed the electronic structure of the Ni(OH)2 nanosheet surface. The electrons would accumulate around the interspace between Zr and neighboring O atoms, which increased the total density of states (DOS) near the Fermi level. Thus, the charge transfer was obviously accelerated, resulting in catalytic activity improvements. As a result, as-prepared Zr-Ni(OH)2 nanosheets exhibited overpotentials of 263 mV at 500 mA/cm2 and 274 mV at 1000 mA/cm2 for the HER, as well as 310 mV at 500 mA/cm2 and 328 mV at 1000 mA/cm2 for the OER. While serving as bifunctional water decomposition electrodes, current Zr-Ni(OH)2 exhibited a cell voltage of 1.595 V at 10 mA/cm2 and a relatively low voltage below 2 V at a large current density of 1000 mA/cm2.