ABSTRACT
The role of adsorbed atomic H in the electrochemistry of various processes involving hydrogen is reviewed. A brief survey of involvement of H in H2 evolution reaction (HER) mechanisms provides the background for discussion of the role of chemisorbed H in electrocatalysis of the HER at various metals, temperature dependence of Tafel slopes of the HER, thermodynamics and kinetics of underpotential deposition (UPD) of H at single-crystal surfaces in relation to the recent outstanding developments in electrochemical surface science, metal-to-H bonding in UPD of H and the entropy and volume of electrosorbed H, chemisorbed H as the source of H sorbed into transition metals, and participation of electrosorbed H in electrochemical hydrogénation processes. The unique situation of the HER as a model reaction for electrode kinetics and electro-sorption is emphasized.
