Theoretical Analysis of the Nature of Hydrogen at the Electrochemical Interface Between Water and a Ni(111) Single-Crystal Electrode

Abstract

The adsorption, absorption, and diffusion of hydrogen on and into metals are elementary processes that are important to a wide variety of electrochemical and corrosion processes. Ab initio gradient corrected density functional theoretical calculations were carried out in order to probe these processes for hydrogen at the aqueous∕Ni(111) interface under well-defined electrochemical conditions. The binding of hydrogen on Ni(111) in the presence of water is considered using a fully atomistic model of the solution environment. We calculate the changes in hydrogen binding energy due to the presence of water at the interface, as well as due to changes in applied potential and surface charge. Binding energies for hydrogen at the hexagonally close-packed and octahedral sites shifted endothermically as the potential was made more anodic, indicating that reductive partial charge transfer occurs. Conversely, hydrogen binding at the tetrahedral site was found to be partially oxidizing. The calculation of vibrational modes allowed the extrapolation of ab initio results to room temperature conditions. Surface Pourbaix diagrams were constructed to predict the chemical states of hydrogen obtained over a Ni(111) single-crystal surface as a function of pH and potential. These calculations indicate that the Tafel recombination mechanism is not active for Ni(111) at 300K , but rather the hydrogen evolution reaction proceeds by the Heyrovsky mechanism following a very short potential span of underpotential deposited hydrogen as one scans the surface cathodically. These results apply to an ideal (111) single-crystal surface in the absence of surface impurities and adsorbed ions (other than hydrogen).

Ab Initio Electrochemistry: Exploring the Hydrogen Evolution Reaction on Carbon Nanotubes

“…the barrier rises, when going towards more anodic potentials. 16 As demonstrated in Sec. 3.5, the nanotube hydrogen coverage rapidly approaches full monolayer once the electrode potential increases beyond the HER onset potential U = −0.34 V. We can use the calculated BEP relationships from Figures 10 and S9 to estimate how the energetics of the Volmer-Heyrovsky mechanism change in the limit of monolayer coverage.…”

First Principles Analysis of the Electrocatalytic Oxidation of Methanol and Carbon Monoxide

“…The validation of the potential and reaction energies determined with the choice as to the number of metal layers in the slab representation [32] and size of the water layer was performed [38]. Herein, we describe the application of this method to the potential dependence of various different elementary chemical processes occurring at a fuel cell electrode.…”

Electrochemical reactions at the electrode/solution interface: Theory and applications to water electrolysis and oxygen reduction

“…The solvation effects have not been considered. Neurock and coworkers proposed a double-reference method to describe the metal/water interface ( Figure 1 (b)), in which the water layers outside the metal surface are explicitly included [7,[67][68][69][70][71]. The electrode surface is represented by the standard slab model, while several layers of water molecules fill the vacuum gap in between the slabs.…”