Quantum electrocatalysts: theoretical picture, electrochemical kinetic isotope effect analysis, and conjecture to understand microscopic mechanisms
The science of electrode processes is attracting enormous interest. Advancing their principles and elucidating the inherent microscopic mechanisms can have a huge impact on the understanding of the fundamental laws of the universe, as well as the knowledge to improve performances of energy conversion/storage devices. Therefore, it has become one of the most important subjects. Based on the recent advancements in the field of quantum electrochemistry, an electrocatalyst enabling the quantum electrode processes, namely, a quantum electrocatalyst, is the focus of this Perspective Review. In particular, quantum-tunneling-driven multielectron/multiproton transfers, in which several electrons and protons are spontaneously and/or sequentially transferred at the electrode/electrolyte interfaces, are mainly discussed. These reactions emerge from the nontrivial interactions between the electrodes, reactants, and solvents; therefore, they are essentially fairly complicated phenomena. Together with the confirmation of the basic experimental tips to reliably measure the electrochemical properties and discussions on how to practically use the electrochemical kinetic isotope effect to analyze complicated energy conversion reactions, this contribution has formulated conjectures with regard to microscopic mechanisms involving key electrode processes, i.e., oxygen reduction reaction and hydrogen evolution reaction, as well as the potential of quantum electrocatalysts toward the further advancement of energy conversion technologies.