The effect of a gradient porous structure on the performance of cold-sprayed electrodes used in alkaline water electrolysis

Transition metal Ni with a low cost and a highly efficient activity is favorable catalyst for alkaline water electrolysis, and often prepared in porous to boost the electrolysis performance, while the mass transportation is inevitable limited. Here, the Ni electrodes with pore-graded structures were obtained from a blend of Ni and Al via high-pressure cold spray. The gradient porosity was realized by varying the addition of Al and applying chemical etching. The obtained electrodes were annealed before the etching to eliminate the residual stress and strengthen the adhesion of layers. The size distribution and connectivity of pores were characterized by scanning electron microscopy (SEM) and industrial Computed Tomography (CT). The effect of gradient porosity on the electrocatalytic activity toward HER/OER was evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results revealed that the prepared pore-graded electrodes exhibited a superior HER/OER performance than normal porous electrodes. Sample N321A with a negative gradient exhibited the best HER/OER performance when tested with an annulus counter electrode of Nickel foam. While sample N123A with a positive gradient exhibited the best HER/OER performance when tested with a carbon rob counter electrode. All prepared electrodes showed an excellent durability after 500 CV cycles.