Unveiling Hydrogen Coverage on Ru Nanoparticles Through Modeling and Experiments

Understanding metal-hydrogen interactions is essential in catalysis research. Hydrogen activation on metal catalysts is crucial in industrially catalytic processes, and measurements of hydrogen uptake are widely used to estimate the dispersion of supported metal catalysts. Here, advanced computational strategies, including density functional theory (DFT), ab initio phase diagrams, ab initio molecular dynamics (AIMD), and deep potential molecular dynamics (DPMD) simulations, are combined with experiments to quantitatively examine hydrogen uptake by Ru at the atomic scale. The results reveal that small Ru nanoparticles (≈1 nm) can adsorb more than two monolayers (ML) of hydrogen (H/Ru > 2) under ambient conditions, while even for larger particles (≈4.8 nm), hydrogen uptake remains higher than 1.2 ML (H/Ru > 1). This size-dependent behavior, confirmed experimentally using high-resolution electron microscopy and chemisorption, challenges the conventional assumption of a uniform 1 ML saturation coverage on surfaces, and indicates that conventional chemisorption analyses may significantly overestimate Ru dispersion or underestimate particle size. Furthermore, DPMD simulations also qualitatively predict hydrogen uptake on Ru surfaces at ambient and working temperatures. The findings provide a more accurate database of Ru-H interactions, correcting for Ru particle size-dependent hydrogen uptake, and can potentially be applied to both academic research and industrial applications.