Out-of-equilibrium catalysis of chemical reactions by electronic tunnel currents

TL;DR

This paper develops a theoretical framework using nonequilibrium Green's functions to describe how electronic currents can catalyze chemical reactions by modifying energy barriers and heating molecules, providing a new perspective beyond vibrational pumping.

Contribution

It introduces an out-of-equilibrium escape rate theory for current-induced reactions, incorporating reaction-coordinate-dependent friction, noise, and temperature effects derived from electronic Green's functions.

Findings

Current-induced catalysis involves barrier reduction and molecular heating.

Resonant tunneling regime enhances dissociation via electronic effects.

The mechanism differs from vibrational excitation paradigms.

Abstract

We present an escape rate theory for current-induced chemical reactions. We use Keldysh nonequilibrium Green's functions to derive a Langevin equation for the reaction coordinate. Due to the out of equilibrium electronic degrees of freedom, the friction, noise, and effective temperature in the Langevin equation depend locally on the reaction coordinate. As an example, we consider the dissociation of diatomic molecules induced by the electronic current from a scanning tunnelling microscope tip. In the resonant tunnelling regime, the molecular dissociation involves two processes which are intricately interconnected: a modification of the potential energy barrier and heating of the molecule. The decrease of the molecular barrier (i.e. the current induced catalytic reduction of the barrier) accompanied by the appearance of the effective, reaction-coordinate-dependent temperature is an alternative mechanism for current-induced chemical reactions, which is distinctly different from the usual paradigm of pumping vibrational degrees of freedom.