Tunable angle-dependent electrochemistry at twisted bilayer graphene with moiré flat bands

Area of Science:

• Materials Science
• Electrochemistry
• Condensed Matter Physics

Background:

• Electron transfer at solid-liquid interfaces is crucial for energy conversion.
• Moiré superlattices in twisted 2D materials allow for engineered electronic properties.
• Flat electronic bands in moiré systems can significantly impact charge transfer.

Purpose of the Study:

• To investigate the twist-angle dependence of heterogeneous charge transfer kinetics in twisted bilayer graphene.
• To understand the role of moiré-derived flat bands in modulating electron transfer.
• To explore the impact of structural relaxation and topological defects on electrochemical activity.

Main Methods:

• Fabrication of twisted bilayer graphene with controlled azimuthal misorientation.
• Electrochemical measurements of charge transfer kinetics using a solution-phase redox couple.
• Experimental and computational analysis, including structural relaxation studies.
• Investigation of moiré superlattice properties and electronic band structures.

Main Results:

• A strong twist-angle dependence of charge transfer kinetics was observed.
• The greatest enhancement in charge transfer occurred near the magic angle (~1.1°).
• Angle-dependent tuning of moiré-derived flat bands was identified as the key driver.
• Structural relaxation and localized flat bands in 'topological defect' AA stacking regions showed anomalous electrochemical enhancement.

Conclusions:

• Twisted bilayer graphene's electrochemical activity is highly sensitive to moiré superlattice structure and twist angle.
• Moiré engineering provides a route to tailor interfacial electron transfer for energy applications.
• The observed enhancement is linked to localized flat bands and structural relaxation, exceeding simple density of states effects.