Electron transfer across a thermal gradient

TL;DR

This paper develops a theoretical framework for electron transfer and heat transport between donor-acceptor pairs at different temperatures, integrating charge and heat flow at the nanoscale with a generalized transition state theory.

Contribution

It introduces a bithermal transition state theory for electron transfer, accounting for temperature differences and heat flow, advancing understanding of nanoscale charge and heat transport.

Findings

Enhanced heat transport occurs via open electron transfer channels at equilibrium.

The theory unifies charge transfer and heat conduction across thermal gradients.

Relations between heat exchange rate and temperature difference are established.

Abstract

Charge transfer is a fundamental process that underlies a multitude of phenomena in chemistry and biology. Recent advances in observing and manipulating charge and heat transport at the nanoscale, and recently developed techniques for monitoring temperature at high temporal and spatial resolution, imply the need for considering electron transfer across thermal gradients. Here, a theory is developed for the rate of electron transfer and the associated heat transport between donor-acceptor pairs located at sites of different temperatures. To this end, through application of a generalized multidimensional transition state theory, the traditional Arrhenius picture of activation energy as a single point on a free energy surface is replaced with a bithermal property that is derived from statistical weighting over all configurations where the reactant and product states are equienergetic. The flow of energy associated with the electron transfer process is also examined, leading to relations between the rate of heat exchange among the donor and acceptor sites as functions of the temperature difference and the electronic driving bias. In particular, we find that an open electron transfer channel contributes to enhanced heat transport between sites even when they are in electronic equilibrium. The presented results provide a unified theory for charge transport and the associated heat conduction between sites at different temperatures.