Pristine and Doped MoS2 Monolayers as Potential HCN Gas Sensors: A DFT Study

TL;DR

This study uses DFT to analyze how pristine and doped MoS2 monolayers can detect HCN gas, identifying promising doped systems with fast response times and notable electronic and optical property changes for sensor applications.

Contribution

It provides a comprehensive DFT analysis of HCN adsorption on various doped MoS2 monolayers, highlighting the effects of different dopants and doping levels on sensing performance.

Findings

Al-MoS2 shows the strongest chemisorption of HCN.

Si-MoS2 exhibits an ultrafast response in microseconds.

2P-MoS2 and 3Al-MoS2 are promising for HCN sensing applications.

Abstract

Two-dimensional transition metal dichalcogenides (TMDCs) have been extensively investigated due to their tunable properties. In this work, density functional theory (DFT) is employed to investigate the adsorption behavior and sensing characteristics of HCN on pristine and doped MoS2 monolayers (X-MoS2, where X = P, N, Si, Al, B, Cl). The structural, electronic, and optical characteristics of all systems are examined to study the sensing properties of various doped MoS2 monolayers. In particular, the Al-MoS2 system demonstrates the strongest adsorption characterized by chemisorption, while the remaining systems show interactions of physisorption type. Recovery time and changes in electronic and optical properties reveal that Si-MoS2 possesses an ultrafast response of the order of microseconds, while Al-MoS2 exhibits a significantly longer recovery time, making it unsuitable for reusable sensors. P-MoS2, Si-MoS2, and Al-MoS2 monolayers show pronounced changes in their properties after HCN adsorption. To explore tunability in adsorption strength and recovery behavior, systems with two and three dopant atoms are further studied for P, Si, and Al doping. The results indicate that double doping enhances adsorption strength, whereas triple symmetric doping weakens it. Based on adsorption energy, recovery time, and electronic response, 2P-MoS2 and 3Al-MoS2 are identified as promising candidates for electrochemical and chemiresistive sensing of HCN. Additionally, the observed optical response in the ultraviolet region highlights their potential in UV-range optical sensor design.