Oxidation kinetics and non-Marcusian charge transfer in dimensionally confined semiconductors

TL;DR

This study investigates the oxidation kinetics of monolayer WS2 and MoS2, revealing a non-Marcusian charge transfer mechanism and how environmental factors influence reaction rates in atomically thin semiconductors.

Contribution

It uncovers a non-Marcusian charge transfer process in 2D semiconductors and correlates oxidation rates with multiple environmental and structural parameters.

Findings

Distinct reaction barriers of 1.4 and 0.9 eV for WS2 and MoS2

Identification of non-Marcusian charge transfer mechanism

Environmental factors significantly influence oxidation kinetics

Abstract

Electrochemical reactions represent essential processes in fundamental chemistry that foster a wide range of applications. Although most electrochemical reactions in bulk substances can be well described by the classical Marcus-Gerischer charge transfer theory, the realistic reaction character and mechanism in dimensionally confined systems remain unknown. Here, we report the multiparametric survey on the kinetics of lateral photooxidation in structurally identical WS2 and MoS2 monolayers, where electrochemical oxidation occurs at the atomically thin monolayer edges. The oxidation rate is correlated quantitatively with various crystallographic and environmental parameters, including the density of reactive sites, humidity, temperature, and illumination fluence. In particular, we observe distinctive reaction barriers of 1.4 and 0.9 eV for the two structurally identical semiconductors and uncover an unusual non-Marcusian charge transfer mechanism in these dimensionally confined monolayers due to the limit in reactant supplies. A scenario of band bending is proposed to explain the discrepancy in reaction barriers. These results add important knowledge into the fundamental electrochemical reaction theory in low-dimensional systems.