LAUSR

Abstract Replacing kinetically sluggish oxygen evolution reaction (OER) with hydrazine oxidation (HzOR) is an effective strategy for water electrolysis to achieve sustainable hydrogen production. Here we report triple-hierarchical nanoporous Ni(Cu)@NiFeP onto nickel foam (NM) as a bifunctional electrocatalyst for HER and HzOR. The as-prepared catalyst with a 54-fold increased electrochemical active surface area (ECSA) presents remarkable HzOR activity, requiring a potential of 6 mV to achieve 10 mA cm−2 in 1 M KOH, which is comparable to commercial Pt/C. Assembling in an electrolyzer for HER and HzOR, the Ni(Cu)@NiFeP/NM cell requires a cell voltage of 0.491 V to offer 100 mA cm−2, far lower than that of overall water splitting. The superior catalytic performance is ascribed to the synergistic effect from crystalline Ni(Cu) alloy and amorphous NiFe P-derivatives, as well as structural advantages of the unique 3D hierarchical porous nanostructures. The study also presents a strategy for accurate design and construction of multiple hierarchy of nanomaterials for energy storage and conversion devices.