On the surface orientation effects of hydrogen mobility on Pt and Ni using atomistic modelling

Green hydrogen offers a sustainable solution for decarbonising industry, transport, and energy storage, yet water electrolysis remains limited by the efficiency and cost of current catalysts. Platinum (111) surface is one of the most effective materials for the hydrogen evolution reaction (HER), but the origins of its superior performance remain unclear. Considering surface diffusion being a key HER step, this study investigated hydrogen adsorption and mobility on (111), (100), and (110) surfaces of platinum and nickel using density functional theory and molecular dynamics. Surface topography influenced adsorption site preference and determined primary hydrogen pathways. Top-site adsorption was material dependent with Pt showing stronger binding than Ni. Pt(111) exhibited the highest hydrogen mobility followed by Ni(100), suggesting a new descriptor for catalyst materials. Hydrogen on (110) surfaces exhibited directional movement, which could enhance catalytic performance. These findings highlight how surface structure can tune hydrogen kinetics, aiding the design of efficient HER catalysts and other surface-mediated reactions. • Platinum (111) exhibited the highest hydrogen mobility, followed by Nickel (100), suggesting a new descriptor for catalyst materials. • Surface topography (crystal orientation) dictates the energy ordering of non-top adsorption sites, thereby controlling the primary pathways of hydrogen motion across materials. • Top-site adsorption stability is strongly material-dependent, being the strongest adsorbing site on Pt surfaces but the weakest on Ni surfaces, which influences hydrogen mobility at higher temperatures. • Hydrogen on (110) surfaces exhibited highly directional movement; this anisotropy could potentially enhance catalytic performance by concentrating adsorbed species despite lower overall diffusivity. • These findings emphasise that surface structure and associated smooth energy landscapes can tune hydrogen kinetics, which is vital for designing efficient HER catalysts.