Tunable electrochemistry with moiré flat bands and topological defects at twisted bilayer graphene

Yun Yu, Kaidi Zhang, Holden Parks, Mohammad Babar, Stephen Carr, Isabel Craig, Madeline Van Winkle, Artur Lyssenko, Takashi Taniguchi, Kenji Watanabe, Venkatasubramanian Viswanathan, D. Kwabena Bediako

Published 2021-08-15Version 1

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.