Efficient Alkaline Hydrogen Evolution Reaction Using Superaerophobic Ni Nanoarrays with Accelerated H2 Bubble Release

Despite the adverse effects of H-2 bubbles adhering to catalyst's surface on the performance of water electrolysis, the mechanisms by which H-2 bubbles are effectively released during the alkaline hydrogen evolution reaction (HER) remain elusive. In this study, a systematic investigation on the effect of nanoscale surface morphologies on H-2 bubble release behaviors and HER performance by employing earth-abundant Ni catalysts consisting of an array of Ni nanorods (NRs) with controlled surface porosities is performed. Both aerophobicity and hydrophilicity of the catalyst's surface vary according to the surface porosity of catalysts. The Ni catalyst with the highest porosity of approximate to 52% exhibits superaerophobic nature as well as the best HER performance among the Ni catalysts. It is found that the Ni catalyst's superaerophobicity combined with the effective open pore channels enables the accelerated release of H-2 bubbles from the surface, leading to a significant improvement in geometric activities, particularly at high current densities, as well as intrinsic activities including both specific and mass activities. It is also demonstrated that the superaerophobicity enabled by highly porous Ni NRs can be combined with Pt and Cr having optimal binding abilities to further optimize electrocatalytic performance.