DFT Path Towards the Characterization of the SnO 2 -CH 4 Gas Sensing Reactions
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.82
DFT Path Towards the Characterization of the SnO2CH4 Gas Sensing Reactions G. Carbajal-Franco1 and M. F. Márquez-Quintana2 1
Division of Graduate Studies and Research, Instituto Tecnológico de Toluca, TecNM-SEP, Avenida Tecnológico, s/n, Colonia Agrícola Buenavista, Metepec, 52149, México
2
Department of Chemistry and Biochemistry, Instituto Tecnológico de Toluca, TecNM-SEP, Avenida Tecnológico, s/n, Colonia Agrícola Buenavista, Metepec, 52149, México
Gas detecting and sensing is a largely studied field of knowledge, but total understanding is not yet achieved and the ideal device is still far in the future. Many experimental efforts have been devoted to find the minimum optimal temperature and operational conditions for SnO 2 to sense hydrocarbons; different methods to build gas-detecting devices keep being developed all around the world, from paste-based bulk devices to nanostructured thick and thin films, but little effort has been aim to characterize the reactions by calculating their related enthalpies. Computational methods have been widely used to characterize, understand and model many physicochemical interactions. In this regard, three main courses can be followed: Ab initio (first principles of quantum mechanics), DFT (Density Functional Theory) and MD (Molecular Dynamics) simulation. In this research, DFT modelling tool is employed to understand and characterize the gas-sensing reactions of Tin Oxide when exposed to an atmosphere with Methane. In CASTEP, a robust DFT module of the Materials Studio suite, one SnO2 (110) crystal plane is exposed to CH4 and the structure is optimized many times for each possible step of the reaction, recording the energies related with each optimization stage, in sum giving us the Transition State (TS) of the reaction. Based on the data, a promising reaction-path is proposed and analyzed for the (110) surface.
INTRODUCTION There are many efforts aimed to the total understanding of the gas-sensing reactions of some metallic oxide-semiconductors. The basic and most followed approach is to model the behaviour based on the experimental results of the material exposed to different gases [1]. As result of this experimentation, Tin Oxide has proved to be one of the most apt materials [1-3]. In this regard, there are already studies that relate the concentration of oxygen species with the reactions occurring in the gas-sensing process [4-7] and a study that characterize the gas sensing reactions of CO on SnO 2 [8] but taking in account the adsorption of oxygen prior to the gas-sensing reactions. Our approach is to make use of the oxygen vacancies that are experimentally proved to be the source of the semiconductor n-type nature of the SnO2 [9-16]. In this work, we focus on the interaction of CH4 on the tin oxide surface. Methane is an important hydrocarbon gas that has been widely used as fuel [17-20], but it also imposes a hazard on the planet climate change [21-22], and even to human health [23]. The st
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