Perspective—New Perspectives from Classical Transition State Theory: The Hydrogen Evolution Reaction on Metal Electrodes

Abstract

New perspectives derive from classical transition state theory applied to hydrogen evolution reactions (HER). Trasatti found exchange current density j 0 increases exponentially with metal electrode work function Φ. The elementary electron transfer step M ( e ) + H ads + ⇄ M ( 0 ) + H ads • specifies the metal in the transition state and derives rate equations where metal specific physiochemical property Φ is explicit. Linearity of log j 0 with Φ is quantified. Φ raises j 0 because Φ lowers the activation energy for electrocatalysis. Rate expressions that embed material specific physiochemical properties provide opportunities for a priori electrocatalyst design and fundamental insights on electron transfer kinetics. New perspectives derive from revisit of established HER data with classical transition state theory.