Quantum-to-Classical Transition of Proton-Transfer in Electrocatalytic Oxygen Reduction

TL;DR

This study investigates how proton transfer in the oxygen reduction reaction on platinum shifts from quantum tunneling to classical behavior depending on the applied potential, combining experimental isotopic ratios with theoretical analysis.

Contribution

It reveals a potential-dependent quantum-to-classical transition in proton transfer during oxygen reduction, supported by experimental isotopic ratios and theoretical confirmation.

Findings

Proton transfer involves tunneling at low overpotentials.

Isotopic rate ratio (kH/kD) decreases from 32 to 3 with increasing potential.

The transition from quantum to classical transfer is theoretically confirmed.

Abstract

The four-electron oxygen reduction reaction on Pt catalyst in alkaline solution undergoes proton transfer via tunneling mechanism. The hydrogen/deuterium kinetic isotopic rate constant ratio (kH/kD ) = 32 in a low overpotential region, indicating the importance of the quantum-proton-tunneling at the rate-determining step (RDS). However, kH/kD goes down to 3 in a high overpotential region, suggesting the classical proton-transfer (PT) scheme. Therefore, there is a quantum-to-classical transition of PT process as a function of potential, which is confirmed by theoretical study.