Protons crossing triple phase boundaries based on a metal catalyst, Pd or Ni, and barium zirconate.

Density functional theory calculations are used to investigate the energetics of protons crossing triple phase boundaries based on a metal catalyst, Pd or Ni, and barium zirconate. Our calculations show that the proton transfer reaction at these interfaces is controlled by the terminal layer of the electrolyte in contact with the metallic and gas phases. The hydrogen spilling process onto the electrolyte surface is energetically favored at peripheral sites of the metal-electrolyte interface, and proton incorporation into the sub-surface region of the electrolyte involves energies of the order of 1 eV. At the triple phase boundary, the energy cost associated with the proton transfer reaction is controlled by both the nature of chemical contact and the Schottky barrier at the metal-electrolyte interface.