Nanoscale redox mapping at the MoS₂-liquid interface.

Area of Science:

• Materials Science
• Electrochemistry
• Surface Science

Background:

• Layered molybdenum disulfide (MoS2) is a key 2D material for photocatalysis, particularly for hydrogen evolution and water splitting.
• Understanding the electronic structure at the MoS2-liquid interface is critical for optimizing catalytic efficiency.
• The band offset at MoS2 surfaces significantly influences catalytic reaction mechanisms and performance.

Purpose of the Study:

• To investigate the heterogeneous charge transfer behavior of MoS2 flakes with varying layer numbers and sizes.
• To resolve the electronic structure at the MoS2-liquid interface with high spatial resolution.
• To gain detailed insights into local processes like band offset and faradaic current confinement.

Main Methods:

• Utilized near-field scanning electrochemical microscopy (NF-SECM) for high-resolution analysis.
• Employed the ferrocene/ferrocenium (Fc/Fc+) redox couple as a probe in organic solutions.
• Combined NF-SECM with additional characterization techniques.

Main Results:

• Redox mapping demonstrated area- and layer-dependent reactivity of MoS2 flakes.
• Provided detailed insights into local processes, including band offset and confined faradaic current.
• Deduced the band alignment at the liquid-solid interface.

Conclusions:

• The study elucidates the electronic properties of MoS2 at the liquid-solid interface.
• Findings are crucial for understanding and improving MoS2-based photocatalytic systems.
• The developed methodology offers a pathway for detailed interfacial analysis in 2D materials.