Thermoneutrality Is Not Necessary to Maximize Oxygen Evolution Reaction Rates

Optimizing the binding energy of reaction intermediates is a central concept toward enhancing electrocatalytic activity. It is widely accepted that the overpotential to initiate the reaction can be minimized when all reaction intermediates have equal energies. Furthermore, the difficulty of achieving such thermoneutral landscapes due to scaling relationships between binding energies has been used as the basis to consider theoretical limits on the activity of oxygen evolution reaction catalysts. However, while thermoneutral landscapes may allow the reaction to be initiated at small overpotentials, its influence on catalytic rates is still unclear. Here, we demonstrate that thermoneutrality is not necessary to maximize rates of the oxygen evolution reaction using a microkinetic model containing both acid-base and direct-coupling mechanisms. Our numerical simulations show that a nonthermoneutral catalyst can exhibit reaction rates comparable to a thermoneutral one if binding energies are tuned such that additional driving force is applied to kinetically unfavorable elementary steps. The drawback to this approach is that the rate of the reverse reaction is significantly diminished. Therefore, while thermoneutrality is necessary to maximize rates for both oxidative and reductive directions, it is not necessary to maximize rates in one direction.