Theoretical and computational studies of semiconductor materials with photocatalytic potential

Abstract

Currently, several environmental problems arising from the rapid progress in urbanization, industrialization and large population growth have been faced by modern society, such as the contamination of air, soil and water. In particular, the main contaminants in effluents and oceans are organic compounds from industrial sedimentation and other compounds extensively present in the daily life of mankind, such as drugs, steroids and hormones, personal care products (fragrances, sunscreen agents, insect repellents ), antiseptics, metabolic surfactants, flame retardants and gasoline additives.In this context, the main methods for water remediation currently employed are adsorption, membrane separations and biological treatment. However, the use of such forms of treatment is not viable, either due to the operational cost, the formation of secondary contaminants in the process or the growth of bacteria whose elimination is even more complex. On the other hand, researchers around the world have been dedicated to the development of new methods for treating effluents. In recent years, heterogeneous photocatalysis has stood out as a promising technology and a high potential alternative for treating effluents contaminated with the most diverse chemical compounds. The interest in this type of process can be justified by the low economic cost, high efficiency, simplified operating conditions and mainly by the use of sustainable and extremely abundant energy: solar radiation. For this reason, the development of new materials for photocatalysis has played a fundamental role in improving the efficiency of photocatalytic degradation processes of the most diverse contaminants. In the present project, the structural, thermodynamic and electronic properties of MnMoO4 will be investigated by means of computational simulations based on the Density Functional Theory. Such material is a semiconductor widely used in the development of energy storage devices, supercapacitors and application in several electrochemical processes. MnMoO4 presents a band gap of approximately 2 eV, indicating the possibility of application in optical processes related to radiation in the visible region. However, to date, the photocatalytic potential of this material has not been reported. Therefore, from the results obtained for the electronic structure, mobility and rate of recombination of the charge carriers (electron-hole pair) it will be possible to determine their photocatalytic potential aiming at its application in photocatalytic processes for effluent treatment, as well as the possibility of production of O2 and H2 through the photocatalytic breakdown of water catalyzed by MnMoO4. In addition, the morphological properties of this material will be investigated in order to determine the relationship between morphology and photocatalytic potential of such material, making it possible to understand which crystalline morphologies are preferred for application as a catalyst in photocatalytic processes. (AU)