Microscopic origin of twist-dependent electron transfer rate in bilayer graphene

TL;DR

This study investigates how the twist angle in bilayer graphene influences electron transfer rates by affecting screening length, density of states, and reorganization energy, providing a microscopic understanding aligned with experimental data.

Contribution

It introduces a molecular simulation and continuum theory framework to connect twist angle with electrochemical kinetics in bilayer graphene electrodes, revealing the microscopic mechanisms involved.

Findings

Electron transfer activation energy increases with screening length.

Twist angle modulates density of states and electron transfer channels.

Theoretical predictions align with experimental observations.

Abstract

Using molecular simulation and continuum dielectric theory, we consider how electrochemical kinetics are modulated by twist angle in bilayer graphene electrodes. By establishing a connection between twist angle and the screening length of charge carriers within the electrode, we investigate how tunable metallicity modifies the statistics of the electron transfer energy gap. Constant potential molecular simulations show that the activation free energy for electron transfer increases with screening length, leading to a non-monotonic dependence on the twist angle. The twist angle alters the density of states, tuning the number of thermally-accessible channels for electron transfer and the reorganization energy by affecting the stability of the vertically excited state through attenuated image charge interactions. Understanding these effects allows us to express the Marcus rate of interfacial electron transfer as a function of twist angle, consistent with a growing body of experimental observations.