# Defect-Engineered Al2CO/Al2Se3 Heterostructure for Enhanced Photocatalytic Water Splitting

## TL;DR

This study explores how defects in a specific material structure improve its ability to split water using light, making it a better photocatalyst.

## Contribution

The paper introduces defect engineering in Al2CO/Al2Se3 heterostructures to enhance photocatalytic water splitting.

## Key findings

- Oxygen and carbon vacancies increase the electronic bandgap, while aluminum vacancies cause a semiconductor-to-metal transition.
- Oxygen vacancies enable the heterojunction to trigger water reduction by modifying the band diagram and creating gap states.
- The heterostructure with oxygen vacancies supports both hydrogen and oxygen evolution reactions with favorable thermodynamic properties.

## Abstract

In this study, we investigate the influence of intrinsic
defects
on the photocatalytic properties of the Al2CO/Al2Se3 heterostructure using first-principles calculations.
The intrinsic defects in the form of oxygen and carbon vacancies in
Al2CO monolayer and interface Al2CO/Al2Se3 appeared to increase the electronic bandgap; however,
aluminum vacancy caused a semiconductor-to-metal transition in the
material. The introduction of oxygen vacancies caused charge transfer
from Al2Se3 to Al2CO, causing electronic
stabilization and revealing the van der Waals interaction in the heterojunction.
The band edge alignment of the pristine Al2CO monolayer
indicated unsuitability for hydrogen evolution, but for the heterojunction,
the appearance of oxygen vacancies modified the band diagram and the
origin of gap states enabling the heterojunction to trigger water
reduction. The modeling of photocatalytic water splitting revealed
that the heterostructure containing oxygen vacancies supports hydrogen
evolution reaction (HER) and oxygen evolution reaction (OER). The
HER is found to be thermodynamically promising on Al and Se sites,
indicating ΔG of −0.091 eV and −0.144
eV, respectively, whereas the OER presented an overpotential of 1.08
V.