Quantum-to-Classical Transition of Proton Transfer in Potential-Induced Dioxygen Reduction.

We report an observation of a quantum tunneling effect in a proton-transfer (PT) during potential-induced transformation of dioxygen on a platinum electrode in a low overpotential (η) region at 298 K. However, this quantum process is converted to the classical PT scheme in the high η region. Therefore, there is a quantum-to-classical transition of the PT (QCT-PT) process as a function of the potential, which is confirmed by theoretical analysis. This observation indicates that the quantum tunneling governs the multistep electron-proton-driven transformation of dioxygen in the low η condition.