Ab initio study of water dissociation on a charged Pd(111) surface

TL;DR

This study uses ab initio calculations to explore how electric fields influence water dissociation on a charged Pd(111) surface, revealing the role of surface charge and zero-point energy in reaction barriers.

Contribution

It provides new insights into the effect of electric fields and surface charge on water dissociation barriers using advanced density-functional theory methods.

Findings

Lowest dissociation barrier occurs at a specific electric field strength.

Zero-point energy remains nearly constant across various electric fields.

Negative surface charge enhances nuclear tunneling effects.

Abstract

Interactions between molecules and electrode surfaces play a key role in electrochemical processes and are a subject of extensive research, both experimental and theoretical. In this manuscript, we address the water dissociation reaction on a Pd(111) electrode surface, modelled as a slab embedded in an external electric field. We aim at unraveling the relationship between surface charge and zero-point-energy in aiding or hindering this reaction. We calculate energy barriers with dispersion-corrected density-functional theory and an efficient parallel implementation of the nudged-elastic-band method. We show that the lowest dissociation barrier, and consequently highest reaction rate, takes place when the field reaches a strength where two different geometries of the water molecule in the reactant state are equally stable. Zero-point energy contributions to this reaction, on the other hand, remain nearly constant across a wide range of electric field strengths, despite significant changes in the reactant state. Interestingly, we show that the application of electric fields that induce a negative charge on the surface can make nuclear tunneling more significant for these reactions.