# First-Principles Calculation of Electronic Energy Level Alignment at Electrochemical Interfaces

## TL;DR

This paper uses first-principles DFT calculations to analyze how solvent molecules influence the electronic energy level alignment at semiconductor-electrolyte interfaces, revealing solvent-induced level shifts and the importance of partial surface coverage.

## Contribution

It introduces a method to quantify solvent-induced energy level shifts at electrochemical interfaces using DFT and potential difference calculations, considering partial surface coverage.

## Key findings

- Solvent molecules cause an up-shift in energy levels, varying with coverage.
- Density of states shape remains largely unchanged near the gap.
- Partial surface coverage affects energy level alignment, as shown by molecular dynamics simulations.

## Abstract

Energy level alignment at solid-solvent interfaces is an important step in determining the properties of electrochemical systems. The positions of conduction and valence band edges of a semiconductor are affected by its environment. In this study, using first-principles DFT calculation, we have determined the level shifts of the semiconductors TiO$_2$ and ZnO at the interfaces with MeCN and DMF solvent molecules. The level shifts of semiconductor is obtained using the potential difference between the clean and exposed surfaces of asymmetric slabs. In this work, neglecting the effects of present ions in the electrolyte solution, we have shown that the solvent molecules give rise to an up-shift for the levels, and the amount of this shift varies with coverage. It is also shown that the shapes of density of states do not change sensibly near the gap. Molecular dynamics simulations of the interface have shown that at room temperatures the semiconductor surface is not fully covered by the solvent molecules, and one must use intermediate values in an static calculations.