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t-Principles Study of the Interaction of H2O2 with the SnO2 (110) Surface M. A. Aghamalyana, *, A. A. Hunanyana, V. M. Aroutiouniana, M. S. Aleksanyana, A. G. Sayuntsa, and H. A. Zakaryana a

Yerevan State University, Yerevan, Armenia *e-mail: [email protected]

Received March 25, 2020; revised April 30, 2020; accepted May 5, 2020

Abstract—The interaction of H2O2 with the stoichiometric surface of (110) SnO2 was studied by first principle methods. Relaxed geometries, adsorption energies, and charge transfer between the molecule and the surface were calculated for several starting configurations of the H2O2 molecule and the SnO2 surface. The most probable adsorption sites and their optimized geometries are presented. Keywords: gas sensors, DFT, tin dioxide, hydrogen peroxide, adsorption, surface, metal oxide DOI: 10.3103/S1068337220030020

1. INTRODUCTION Hydrogen peroxide (H2O2) is a chemical compound that is widely used in fields such as medicine, pharmacology, food processing, and textiles. However, pure H2O2 at high concentrations and certain external conditions is explosive [1]. Concentrated peroxide solutions can cause burns on contact with skin, mucous membranes and respiratory tract [2]. Therefore, the development of sensors for its detection and concentration measurement in the environment is an important task. Measurement of the H2O2 concentration in the exhaled air can also be used to diagnose and monitor certain diseases [3]. It is known that vapors of hydrogen peroxide can be detected using semiconductor gas sensors based on metal oxides [4, 5]. Metal oxides, such as SnO2, ZnO, In2O3, etc., have been studied extensively for their response to oxidizing and reducing gases. Typically, gas-sensitive metal oxide materials are porous thick films. Molecular adsorption or the reaction of molecules with the gas sensor surface leads to a change in electrical conductivity. This change can be easily detected and is often used as a signal for gas adsorption. The basic mechanism that causes the conductivity of the material to change upon adsorption or reaction of molecules at the surface is a consequence of the chemical state of the adsorbed species. Charge transfer from the oxide to the chemi- or ionosorbed molecule causes a net surface charge. Because of this surface charge a space charge region is induced in the surface region of the oxide- semiconductor that balances the charges at the surface [6, 7]. This region of space charge is described by the bending of the energy level zones or by a change in the chemical potential of the charge carriers, i.e., a shift in the Fermi level, and thus causes the accumulation or decrease of charge carriers depending on the sign of the surface charge. Consequently, a change in charge carrier concentration due to adsorbate induced band bending is the cause for the signal in the solid-state gas sensors. Tin dioxide is one of the most commonly used materials in commercial gas sensors [8, 9]. This is a wide-gap semiconductor with a band gap of 3.6 eV [10]. Due to the electro