Abstract
Alkaline water electrolysis is currently the most promising approach to produce hydrogen. However, a main limitation for large-scale application originates from the significant energy loss caused by the coverage of bubbles on the electrode surface. Here, pore-graded Ni electrodes with a positive and negative gradient porous structure that boosts the desorption and release of gas bubble are reported, resulting in a greatly advanced mass transference. The electrodes are obtained from a blend of Ni and Al via high-pressure cold spray. The gradient porosity is realized by varying the addition of Al and chemical etching. As-sprayed electrodes are annealed to eliminate the residual stress and strengthen the adhesion of layers, hence improving their durability. As a result, the electrode with a positive pore-graded structure exhibits a better HER/OER performance when tested with a carbon rob counter electrode. Notably, when tested with an annulus counter electrode of Nickel foam, the electrode with a negative pore-graded structure achieves minimal HER/OER overpotential, outperforming other porous electrodes. This is benefited from improved bubble removal and mass transference capability. All prepared electrodes showed an excellent stability that after 500 cycles of HER/OER test without a large potential fluctuation.
