Enhanced Electrochemical Activity Volcanoes in Flat-Band Twisted Trilayer Graphene

Abstract

Electrochemical reactions at electrode-electrolyte interfaces are often controlled by modifying the substrate and thereby tuning the adsorption energy to reach peaks of activity volcanoes. In this work, we attempt to enhance interfacial charge transfer kinetics through modifying the electronic density of states of an electrode which offers highly tunable flat bands such as the twisted graphene system, allowing greater overlap with the redox couple states. Correspondingly, we develop a twist-dependent electrochemical activity map, combining a tight-binding electronic structure model with modified Marcus-Hush-Chidsey kinetics in trilayer graphene. We identify a counterintuitive rate enhancement region spanning the magic angle curve and incommensurate twists of the system geometry. At room temperature, we find a broad activity peak with a ruthenium hexamine redox couple in regions corresponding to both magic angles and incommensurate angles, a result qualitatively distinct from the twisted bilayer case. Flat bands and incommensurability offer new avenues for reaction rate enhancements in electrochemical transformations.