  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.
