What question did this study set out to answer?

The study aims to explore how transition metals affect cyanide gas adsorption on CrS2 monolayers.

December 12, 2025

Adsorption and Sensing of Cyanide Gases over Transition Metal (Mn and Fe)-Decorated CrS 2 Monolayers: Insights from DFT and AIMD Simulations

SSSonam SonamGanesh Shankar Vidyarthi Memorial Medical College NGNeetu Goel

Key Points

The study aims to explore how transition metals affect cyanide gas adsorption on CrS2 monolayers.
Investigated adsorption of cyanide gases using density functional theory.
Compared pristine and transition metal-decorated CrS2 monolayers for gas sensing capabilities.
Analyzed changes in band gap and adsorption energy with transition metal decoration.
Transition metals Mn and Fe significantly improve the adsorption capabilities of CrS2 monolayers.
Adsorption energy was highest for CNBr and lowest for HCN in both decorated monolayers.
Mn-CrS2 showed prolonged recovery times, while Fe-CrS2 exhibited faster recovery, indicating usability as sensors.

Abstract

The present study proposes to comprehensively investigate the adsorption of toxic cyanide gases (HCN, CNF, CNCl, CNBr, and NCCN) on pristine and transition-metal (TM)-decorated CrS2 monolayers using van der Waals-corrected density functional theory. The weak adsorption capability of pristine CrS2 renders it unsuitable for use as a gas sensor; therefore, the monolayer was decorated with TMs, Mn, and Fe. Among the plausible decoration sites, TMs prefer to bind on the TCr site of the CrS2. The energetic stability of the modified monolayers is ensured by high negative values of binding energies, i.e., -5.530 eV for Mn and -5.358 eV for Fe-CrS2. The Mn and Fe decoration significantly improves the surface activity of the intrinsic CrS2 by reducing the band gap (0.080 eV for Mn and 0.610 eV for Fe) and work function (4.945 eV for Mn and 5.173 eV for Fe). Compared with pristine CrS2, the gas adsorption energy of the modified monolayers is greatly improved, and the adsorption distance is enormously reduced, indicating that modification of the monolayer with the TMs enhances the gas sensitivity of CrS2 for toxic cyanide gases. The adsorption energy order is CNBr > CNF > NCCN > CNCl > HCN and NCCN > CNBr > CNF > CNCl > HCN for Mn and Fe-CrS2 monolayers, respectively. The adsorption effects of the target gases were compared and analyzed from the perspectives of the change of band gap, charge density difference, energy band structures, and partial density of states plots. The efficacy of the decorated monolayers for gas sensing was assessed in terms of work function, recovery time, and sensitivity measurements. The comparative analysis revealed that the Mn-CrS2 exhibits high adsorption strength and hence prolonged recovery times for the cyanide gases, signifying its potential as an effective adsorbent. On the contrary, the Fe-CrS2 monolayer shows optimum adsorption strength and faster recovery behavior, emerging as a reusable gas sensor. Overall, this study provides a theoretical framework and opens up new avenues for the design and experimental investigation of high-performance CrS2-based gas sensors to detect hazardous cyanide gases.

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