Noble-metal-free, efficient and stable bifunctional catalysts capable of catalyzing oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are eagerly desired for the commercialization of water splitting electrolysers. Bimetal iron/nickel hydroxide represents a promising water splitting catalyst for its high intrinsic activity, high stability, low cost and nontoxic. To enhance its conductivity and density of active sits, we proposed a mild corrosion assisted protocol to composite FeNi(OH)_x nano-sheets with coral-like Ni. These nanosheets together with the electrodeposited coral-like Ni skeleton and the supermacroporous Ni foam substrate constituted a binder-free hierarchical electrode architecture, which is beneficial for exposing catalytic active sites, enhancing mass transport and accelerating dissipation of gaseous species. In 1.0 M KOH solution, the rational designed electrode presented not only magnificent OER catalytic performance with a low overpotential to reach 50 mA cm^-2 (η = 254 mV), excellent kinetic (Tafel slop of 45 mV dec^-1) and favorable durability, but also superior HER catalytic capability with high activity (η = 68 mV at 10 mA cm^-2) and stability. In addition, a symmetric alkaline electrolyser constructed with FeNi(OH)x/Ni as both anode and cathode exhibited better activity (cell voltage of 1.52 V at 10 mA cm^-2) than that of the precious metal based couple (i.e. RuO₂ - 20 wt% Pt), making FeNi(OH)x/Ni to be a fascinating candidate for overall water splitting.

Key words: Overall water splitting, Integrate electrode, electro-catalysis