Hierarchical nanoporous Ni(Cu) alloy anchored on amorphous NiFeP as efficient bifunctional electrocatalysts for hydrogen evolution and hydrazine oxidation

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.