Effect of the thickness of nickel electrode with aligned porous structure on hydrogen evolution reaction

Abstract

Seven nickel electrodes with aligned porous structure of different thicknesses (i.e., 100, 250, 400, 500, 600, 850, and 1100 μm) were fabricated via freeze casting, and the effect of the electrode thickness on hydrogen evolution reaction (HER) was experimentally studied. The polarization curves of the porous electrodes were obtained by linear sweep voltammetry (LSV) in a 1 M KOH solution. The results show that, in the lower current density zone, the overpotential decreases with the increasing thickness of the aligned porous electrode. At higher current density, the overpotential presents a relative complex variation with the electrode thickness. For a thicker porous electrode, its electrochemically active surface area (ECSA) undoubtedly increases. Nevertheless, its bubble removal ability decreases due to deeper porous channels, which adversely affects the HER performance. It is also found that while the aligned pore orientation of the electrode is parallel to gravity direction, the electrode with a thickness of 400 μm has a trade-off between the ECSA and bubble removal ability and shows optimal performance. • Seven nickel electrodes with aligned porous structure of different thicknesses were fabricated by freeze casting. • The thickness of the electrode has little effect on the pore size distribution, but has a significant effect on HER. • The pore orientation of aligned porous electrodes also has effect on HER.