Kavli Affiliate: David T. Limmer
| First 5 Authors: Sonal Maroo, Sonal Maroo, , ,
| Summary:
Electron transfer (ET) reactions underpin energy conversion and chemical
transformations in both biological and abiological systems. The efficiency of
any ET process relies on achieving a desired ET rate within an optimal driving
force range. Marcus theory provides a microscopic framework for understanding
the activation free energy, and thus the rate, of ET in terms of a key
parameter: the reorganization energy. For electrified solid-liquid interfaces,
it has long been conventionally understood that only factors in the electrolyte
phase are responsible for determining the reorganization energy and the
electronic density of states (DOS) of the electrode serves only to dictate the
number of thermally accessible channels for ET. Here we show instead that the
electrode DOS plays a central role in governing the reorganization energy, far
outweighing its conventionally assumed role. Using atomically layered
heterostructures, we tune the DOS of graphene and measure outer-sphere ET
kinetics. We find the ensuing variation in ET rate arises from strong
modulation in a reorganization energy associated with image potential
localization in the electrode. This work redefines the traditional paradigm of
heterogeneous ET kinetics, revealing a deeper role of the electrode electronic
structure in interfacial reactivity.
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