Uncovering Hydrogen Adsorption: A DFT Forecast on Transition Metal Surfaces

The hydrogen evolution reaction (HER) has been widely studied due to the increasing demand for hydrogen as fuel. However, the lack of efficient storage methods restricts the broad adoption of hydrogen-powered devices. Understanding transition metals' hydrogen adsorption capacity is essential for the better design of these devices because they are frequently used as catalysts for many kinds of hydrogen evolution reactions.

The first-principle DFT calculation was carried out using the VASP package to obtain the optimized geometries of hydrogen adsorption on metal surfaces. Two sets of surfaces—a) coinage metals (Ag, Au, and Cu) and b) non-coinage metals (Pt, Pd, Ni, and Co)—are considered. On each metal surface, the hydrogen adsorption energies are obtained at varying surface coverage ratios until the hydrogen evolution is kinetically and thermodynamically spontaneous.

The hydrogen adsorption energies decreased on all metal surfaces with increased hydrogen atoms on the surface. Later, the Tafel hydrogen evolution mechanism is used to define the spontaneous hydrogen evolution from the surfaces. The hydrogen evolution is quicker on the Au surface, and non-coinage metals, namely Ni, Co and Pd, have slower hydrogen evolution. Due to the strong adsorption of hydrogen atoms on metal surfaces, hydrogen atoms are found on the surface even after the HER, which experimental studies have also validated.