The developement of highly active and earth-abundant bifunctional electrocatalysts is a key for water splitting. Currently, transition metal nickel with low cost and high efficient is extremely promsing as water splitting electrocatalysts. This report shows 3D porous nickel electrodes with different porous structure prepared by high-pressure cold spray as electrocatalysts of water splitting. The post annealing is applied to promote the evolution of NiAl intermetallic compound in situ and the adhesion of layers. The micromorphology and composition of the coatings altered by manipulate the temperature of post annealing, the effect of pore former addition and post annealing temperature on the electrocatalytic activity of the popous electrodes towards HER/OER is analyzed. Scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) are used to evaluate the effect of porosity and post annealing temperature on the micromorphology and element state of the porous electrodes. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) is used to evaluate electrocatalytic performance of the electrodes. Notably, the electrodes shows better electrocatalytic performance compared with the bare perforated Ni sheet (COS) toward HER/OER. Besides, benefitting from loose and porous microstructure, NiO-derived NiOOH makes the sample N30A after 400℃ post annealing (C2+N30A) performs the best electrocatalytic performance with 30 mV overpotential in 10 mA/cm² toward HER and 400 mV overpotential in 30 mA/cm² toward OER. And the electrodes also exhibit the strong long-term electrochemical durability in 1.0 M KOH.
 

Porous nickel electrodes; High pressure cold spray; Post annealing; Alkaline water splitting