Understanding Electron Transfer Reactions Using Constrained Density Functional Theory: Complications Due to Surface Interactions

Arsalan Hashemi; Pekka Peljo; Kari Laasonen

doi:10.1021/acs.jpcc.2c06537

Understanding Electron Transfer Reactions Using Constrained Density Functional Theory: Complications Due to Surface Interactions

J Phys Chem C Nanomater Interfaces. 2023 Feb 9;127(7):3398-3407. doi: 10.1021/acs.jpcc.2c06537. eCollection 2023 Feb 23.

Authors

Arsalan Hashemi¹, Pekka Peljo², Kari Laasonen¹

Affiliations

¹ Research Group of Computational Chemistry, Department of Chemistry and Materials Science, Aalto University, FI-00076 Aalto, Finland.
² Research Group of Battery Materials and Technologies, Department of Mechanical and Materials Engineering, Faculty of Technology, University of Turku, 20014 Turun Yliopisto, Finland.

Abstract

The kinetic rates of electrochemical reactions depend on electrodes and molecules in question. In a flow battery, where the electrolyte molecules are charged and discharged on the electrodes, the efficiency of the electron transfer is of crucial importance for the performance of the device. The purpose of this work is to present a systematic atomic-level computational protocol for studying electron transfer between electrolyte and electrode. The computations are done by using constrained density functional theory (CDFT) to ensure that the electron is either on the electrode or in the electrolyte. The ab initio molecular dynamics (AIMD) is used to simulate the movement of the atoms. We use the Marcus theory to predict electron transfer rates and the combined CDFT-AIMD approach to compute the parameters for the Marcus theory where it is needed. We model the electrode with a single layer of graphene and methylviologen, 4,4'-dimethyldiquat, desalted basic red 5, 2-hydroxy-1,4-naphthaquinone, and 1,1-di(2-ethanol)-4,4-bipyridinium were selected for the electrolyte molecules. All of these molecules undergo consecutive electrochemical reactions with one electron being transferred at each stage. Because of significant electrode-molecule interactions, it is not possible to evaluate outer-sphere ET. This theoretical study contributes toward the development of a realistic-level prediction of electron transfer kinetics suitable for energy storage applications.