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

Abstract Electrochemical reaction represents an essential action in fundamental chemistry that fosters wide applications. Although most electrochemical reactions involving bulk substances can be well described by the classical Marcus-Gerischer charge transfer theory, the realistic reaction character and mechanism in atomically confined systems remain unknown. Here, we report the multiparametric survey on the kinetics of lateral photooxidation in WS2 and MoS2 monolayers, where electrochemical reactions occur at the atomically thin flake edges, by quantitatively correlating its reaction rate with various crystallographic and environmental parameters, including density of lattice vacancies, humidity, temperature, and illumination fluence. In particular, we uncover an unusual non-Marcusian charge transfer mechanism in these spatially confined semiconductors due to limit in reactant supplies, where band bending played a crucial role and distinctive reaction barriers (1.4 versus 0.9 eV) are extracted from these analogous materials. These results add important knowledge into the fundamental electrochemical reaction theory.