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Article Citation - WoS: 8Citation - Scopus: 9Electronic, Optical and Thermodynamic Characteristics of Bi12sio20 Sillenite: First Principle Calculations(Elsevier Science Sa, 2021) Isik, M.; Surucu, G.; Gencer, A.; Gasanly, N. M.Bi12XO20 (X: Si, Ge, Ti) ternary semiconducting compounds are known as sillenites and take a remarkable attention thanks to their attractive photorefractive properties. The present paper reports electronic, optical and thermodynamic characteristics of Bi12SiO20 by means of density functional theory (DFT) calculations. The crystalline structure of the compound was revealed as cubic with lattice constant of 10.135 angstrom. XRD pattern obtained from DFT calculations were compared with experimental data and there is a good consistency between them. The electronic band structure and density of state plots were presented in detail. The band gap energy of the compound was determined from electronic band structure and spectra of optical constants. The spectral dependencies of real and imaginary components of dielectric function, refractive index, extinction coefficient, absorption coefficient and loss function were plotted in the 0-12 eV spectral range. The revealed structural, electronic and optical characteristics were discussed taking into account the previously reported theoretical and experimental studies on the Bi12SiO20 sillenite.Book Part Hydrogen Production: Electrolysis Methods(Elsevier, 2025) Celebi, C.; Altınışık, H.; Atak, Y.N.; Çolpan, C.; Devrim, Y.Electrolyzers are at the forefront of sustainable energy technologies, which are important in converting electrical energy into storable and transportable chemical energy. Electrolyzers enable the production of environmentally friendly green hydrogen using excess electricity from renewable sources, thereby reducing outage problems and facilitating grid balancing. Furthermore, using hydrogen as an energy carrier has great potential for decarbonizing hard-to-decarbonize sectors such as heavy industry, aviation and shipping. This chapter provides a comprehensive overview of electrolyzers, covering their basic principles, their various types and their significant importance in the transition to a greener energy environment. The chapter first discusses the basic operation of electrolyzers and explains the electrochemical processes involved in decomposing water molecules into hydrogen and oxygen gases. Each type of electrolyzer is discussed in detail, highlighting their unique features, efficiency, scalability, and technological advancements. Comparative analysis between electrolyzer types provides insights into their suitability for various applications and deployment scenarios. In conclusion, this chapter highlights the critical role of electrolyzers in enabling the hydrogen economy and advocates for continued research, development and deployment efforts to harness their full potential in moving towards a sustainable and carbon-neutral future. © 2025 Elsevier Inc. All rights are reserved, including those for text and data mining, AI training, and similar technologies.Book Part Fuel Cell Energy Conversion(Elsevier, 2025) Ercelik, M.; Nalbant, Y.; Çolpan, C.; Ismail, M.S.Fuel cells are electrochemical devices that convert the chemical energy of the fuel into electrical energy directly. There are different types of fuel cells, which can be categorized according to their electrolyte type and fuel used. The performance of these fuel cells mainly depends on the materials of their components and the manufacturing method. In this chapter, an introduction to different fuel cell types, the materials and manufacturing methods that can be used for fuel cells, and characterization techniques are first presented. Then, the basic concepts and equations for the thermodynamics and electrochemistry of fuel cells are given. The principles of fuel cell stack design including the calculations of pressure drop within a flow field are discussed. Energy and exergy analyses of integrated fuel cells systems are also presented. This chapter also covers several illustrative examples and a case study on the mathematical modeling of fuel cells. © 2025 Elsevier Inc. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
