posted on 2017-11-01, 00:00authored bySaad Intikhab, Joshua D. Snyder, Maureen H. Tang
The sluggish kinetics
of the alkaline hydrogen electrode have been
attributed to the need to adsorb both H and OH optimally. In this
work, single-crystal voltammetry and microkinetic modeling show that
an OH-mediated mechanism is not viable on Pt(110). Only a direct Volmer
step can explain observed kinetic trends with OH adsorption strength
in KOH and LiOH electrolytes. Instead, OH behaves as a rapidly equilibrated
spectator species that decreases available surface sites and slows
hydrogen kinetics. These results identify kinetic barriers from interfacial
water structure, not adsorption energies, as key to explaining changes
in hydrogen kinetics with pH.