# Spontaneous doping of the basal plane of MoS2 single-layers through oxygen substitution under ambient conditions

## TL;DR

This study reveals that oxygen spontaneously substitutes sulfur atoms in MoS2 single-layers under ambient conditions, creating active sites that significantly enhance catalytic activity for hydrogen evolution.

## Contribution

It uncovers the spontaneous oxygen doping process in MoS2 basal planes and links it to increased catalytic performance, a novel insight into MoS2 chemistry.

## Key findings

- Oxygen atoms incorporate into MoS2 basal plane during ambient exposure.
- Oxygen substitution creates active sites for catalysis.
- Enhanced electrochemical H2 evolution activity observed.

## Abstract

The chemical inertness of the defect-free basal plane confers environmental stability to MoS2 single-layers, but it also limits their chemical versatility and catalytic activity. The stability of the pristine MoS2 basal plane against oxidation under ambient conditions is a widely accepted assumption in the interpretation of various studies and applications. However, single-atom level structural investigations reported here reveal that oxygen atoms spontaneously incorporate into the basal plane of MoS2 single layers during ambient exposure. Our scanning tunneling microscopy investigations reveal a slow oxygen substitution reaction, upon which individual sulfur atoms are one by one replaced by oxygen, giving rise to solid solution type 2D MoS2-xOx crystals. O substitution sites present all over the basal plane act as single-atomic active reaction centers, substantially increasing the catalytic activity of the entire MoS2 basal plane for the electrochemical H2 evolution reaction.

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Source: https://tomesphere.com/paper/1904.01411