Tunable electrochemistry with moir\'e flat bands and topological defects at twisted bilayer graphene

TL;DR

This study demonstrates how twisting bilayer graphene at specific angles creates moiré flat bands that significantly influence charge transfer kinetics, revealing a new tunable platform for electrochemical applications.

Contribution

It uncovers the angle-dependent electrochemical behavior of twisted bilayer graphene, highlighting the role of moiré flat bands and topological defects in modulating electron transfer.

Findings

Charge transfer is maximized near the magic angle (~1.1°).

Atomic reconstruction and topological defects enhance electrochemical activity.

Moiré flat bands serve as a tunable platform for electrochemical control.

Abstract

Tailoring electron transfer dynamics across solid-liquid interfaces is fundamental to the interconversion of electrical and chemical energy. Stacking atomically thin layers with a very small azimuthal misorientation to produce moir\'e superlattices enables the controlled engineering of electronic band structures and the formation of extremely flat electronic bands. Here, we report a strong twist angle dependence of heterogeneous charge transfer kinetics at twisted bilayer graphene electrodes with the greatest enhancement observed near the 'magic angle' (~1.1 degrees). This effect is driven by the angle-dependent tuning of moir\'e-derived flat bands that modulate electron transfer processes with the solution-phase redox couple. Combined experimental and computational analysis reveals that the variation in electrochemical activity with moir\'e angle is controlled by atomic reconstruction of the moir\'e superlattice at twist angles <2 degrees, and topological defect AA stacking regions produce a large anomalous local electrochemical enhancement that cannot be accounted for by the elevated local density of states alone. Our results introduce moir\'e flat band materials as a distinctively tunable paradigm for mediating electrochemical transformations.