Effect of kinetic properties of zeolites on the gas-sensing performance of zeolite-covered SnO₂ sensors

ABSTRACT

Zeolite additional layers coating on metal oxide surfaces to improve the selectivity and response values of the sensors are effective and widely used. The specific adsorption and diffusion of gas molecules in the zeolite are recognised to play an important role in gas sensing improvement. In this work, the adsorption and diffusion behaviours of formaldehyde and acetone in H-Y and H-A zeolites were calculated by Monte Carlo and molecular dynamics simulations. The loading of acetone is greater than formaldehyde in these two kinds of zeolites under the same temperature and pressure, and the water load is lower. The simulation results show that the effects of the nature of the guest molecule and steric hindrance of the diffusing molecule on diffusivity are significant. The diffusivity in H-A zeolite decreases by several orders of magnitude than that in H-Y zeolite However, in H-A zeolite, the internal diffusion dominates, and only the smaller diameter formaldehyde can diffuse between the pores, which is beneficial to improving the sensing properties of formaldehyde. In addition, in the competition diffusion with water molecules, formaldehyde dominates than acetone. The H-Y/SnO₂ and H-A/SnO₂ sensors were prepared to verify the reliability of the molecular simulations.

Research highlights

• The adsorption and diffusion behaviour of formaldehyde and acetone in H-Y and H-A zeolites were investigated using molecular simulation.

• Molecular diameter mainly influences the kinetic behaviour.

• The sensitisation mechanism of H-Y/SnO₂ sensor to acetone and H-A/SnO₂ sensor to formaldehyde was proved.

• Focuses on the relationship between gas-sensing the performance of zeolite-covered SnO₂ sensors and the adsorption.

KEYWORDS:

• Molecular simulation
• Monte Carlo
• molecular dynamics
• zeolite
• gas-sensing

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Fundamental Research Funds for the Central Universities [grant number]; National Natural Science Foundation of China [grant number 61574025]; Natural Science Foundation of Liaoning Province [grant number 20180550624]; Dalian Minzu University Special Project of Serving National Strategy [grant number 2020fwgj008].