One-spot autogenous formation of crystalline-amorphous Ni3S2/NiFeO Hy heterostructure nanosheets array for synergistically boosted oxygen evolution reaction

We proposed a convenient heterostructure engineering strategy to integrate ultra-small Nickel sulfide (Ni3S2) laminar nanocrystallines and amorphous NiFe-(oxy) hydroxides (NiFeOxHy) nanosheets as three-dimensional (3D) freestanding catalyst to regulate electric conductivity and boost mass transport by one-step hydrothermal method. These super-hydrophilic Ni3S2/NiFeOxHy heterostructure nanosheets with large specific surfaces can create strongly synergistic couplings of accessible active sites at the interfaces, expedite the electrolyte penetration and make gas bubbles to rapidly release the surface, significantly facilitating intrinsic the kinetics for oxygen evolution reaction (OER). Intriguingly, the self-supported Ni3S2/NiFeOxHy heterostructure nanosheets array displays remarkable OER activity with ultralow overpotentials of only 209 and 243 mV at 50 and 100 mA cm−2, small Tafel slope of 79.8 mV dec−1, as well as good stability up to 55 h. Also, the Ni3S2/NiFeOxHy heterostructure demonstrates an acceptable activity for hydrogen evolution reaction (HER) delivered 10 mA cm−2 at an overpotential of 172 mV. In addition, the Ni3S2/NiFeOxHy can also be served as bifunctional electrocatalyst assembled in a two-electrode configuration with a perfect voltage of 1.32 V to reach 10 mA cm−2 under industrial condition at 85 °C in 6 M KOH for overall water splitting.