Scalable oxygen-assisted-Fe2+ etching approach towards amorphous/crystalline structure Fe-Ni2P nanoarray for efficient water splitting

Developing cheap, stable, and efficient overall water-splitting catalysts for practical applications is desirable. At present, most reported bifunctional catalysts are unsatisfactory in terms of their complicated synthetic procedures. Herein, a low-cost superior water-splitting catalyst, Fe doped nickel phosphide (Fe-Ni2P) nanoflower array has been constructed by a novel and facile synthetic approach that using Fe2+ oxidize into Fe3+ in air to slowly etch Ni foam (NF) and then phosphatizing. The optimized Fe-Ni2P @ NF exhibited a uniform chrysanthemum-like morphology to achieve high exposure active sites, and the amorphous/crystalline homogeneous structure and Fe species doping can modulate the active-site electron state to enhance the intrinsic activity of catalyst. Eventually, this catalyst shows excellent bifunctional catalytic activity, requiring small overpotentials of 71 mV to reach 10 mA cm–2 for hydrogen evolution reaction and 254 mV to reach 50 mA cm–2 for oxygen evolution reaction in 1.0 M KOH. An electrolyzer employed Fe-Ni2P @ NF as both cathode and anode deliver 10 mA cm–2 at a low cell voltage of 1.44 V for overall water splitting. The Fe-Ni2P @ NF also exhibits excellent stability in long-time alkaline water splitting. Additionally, Fe-Ni2P @ NF expanded sample with a 25 × 20 cm2 area was prepared and showed good uniformity of electrocatalytic performance, the assembled two-electrode cell achieves an industrially relevant current density of 500 mA cm−2 requires only 2.7 V voltage.