Optical Imaging of Chemically and Geometrically Controlled Interfacial Diffusion and Redox in 2D van der Waals Space

TL;DR

This study uses optical imaging to investigate how geometric and chemical modifications influence interfacial oxygen diffusion and redox reactions in 2D materials, revealing key factors affecting charge transfer kinetics.

Contribution

It introduces a method to manipulate and visualize interfacial diffusion and redox processes in 2D TMDs, advancing understanding of their reaction dynamics.

Findings

Interfacial gap size and defects significantly affect O2 diffusion and charge transfer.

Charge transfer kinetics vary with hydration levels across different TMDs.

Real-time photoluminescence imaging effectively captures spatiotemporal reaction dynamics.

Abstract

Molecular motions and chemical reactions occurring in constrained space play key roles in many catalysis and energy storage applications. However, its understanding has been impeded by difficulty in detection and lack of reliable model systems. In this work, we report geometric and chemical manipulation of O2 diffusion and ensuing O2-mediated charge transfer (CT) that occur in the 2D space between single-layer transition metal dichalcogenides (TMDs) and dielectric substrates. As a sensitive real-time wide-field imaging signal, charge-density-dependent photoluminescence (PL) from TMDs was used. The two sequential processes inducing spatiotemporal PL change could be drastically accelerated by increasing the interfacial gap size or introducing artificial defects serving as CT reaction centers. We also show that widely varying CT kinetics of four TMDs are rate-determined by the degree of hydration required for the reactions. The reported findings will be instrumental in designing novel functional nanostructures and devices.