Person:
Madero Castro, Rafael María

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First Name
Rafael María
Last Name
Madero Castro
Affiliation
Universidad Pablo de Olavide
Department
Sistemas Físicos, Químicos y Naturales
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Now showing 1 - 2 of 2
  • Publication
    Modelling and molecular simulation of alcohols in porous materials
    (2022) Madero Castro, Rafael María; Calero, Sofia ; Vicent Luna, José Manuel
    This thesis deals with alcohols and water confined in porous materials for applications such as storage, separation or energy transfer. Alcohols can contain one or several hydroxyl groups (-OH simply linked by a covalent bond to a carbon atom. This carbon can be part of a chain of alkanes, alkenes or alkynes, or part of an aromatic ring. Possible configurations of existing alcohols are almost unlimited, which makes systematic studies costly. In this context, advanced simulation techniques can be useful. Monte Carlo simulations, molecular dynamics or energy minimizations provide relevant information on the physicochemical properties of alcohols and their behaviour in the pure state, in mixtures with other alcohols or with water and their interaction with porous materials. Simulation techniques were used in this thesis to evaluate: Storage of alcohols in a highly hydrophobic MOF. In this chapter, the adsorption of methanol, ethanol, propanol and butanol in the porous material MAF-6 has been studied. MAF-6 is a highly hydrophobic and stable adsorbent with high capacity. The results of this work indicate that nucleation by hydrogen bonding is the main mechanism governing the adsorption of alcohols on this hydrophobic adsorbent. This results in steep isotherms reaching high saturation capacity values. Nucleation takes place at values below the saturation pressure of each fluid and involves high energy exchange in the adsorption and desorption regimes. Further analysis revealed the existence of binding sites favouring the nucleation of alcohol molecules and the absence of diffusion limitations for light alcohols through the pores of this MOF. Dehydration of alcohols in equimolar mixtures using membranes composed of pure silica zeolites. In this chapter, the separation of methanol and ethanol with water has been studied using pervaporation membranes composed of MFI zeolite. Liquid mixtures of alcohol and water have been investigated by concentration-guided molecular dynamics finding that the mutual interaction between the alcohol and water molecules makes the membrane unable to completely dehydrate the alcohol samples, although it achieves excellent separation. Use of activated carbons in combination with alcohols for energy storage. This chapter explores the use of linear alcohols (methanol, ethanol, 1-propanol and 1-butanol) in combination with activated carbons derived from the pyrolysis of mineral coke to store thermal energy. The results suggest that the activated carbons studied can store a large amount of thermal energy. This is due to the synergy of the adsorbed molecules and their interaction with the internal surface of the adsorbent. The selected activated carbon (CS1000a) improves the performance for energy storage applications compared to other commercial samples, being a promising alternative for industrial applications. Study of water and alcohol adsorption on zeolites with cations and their use for energy storage. In this chapter, the adsorption of water and methanol on faujasites (FAU) has been studied by varying the cation concentration using quasi-equilibrium temperature programmed desorption and adsorption measurements and Grand Canonical Monte Carlo simulations. In addition, using the methodology proposed in the previous chapter, the energy density that the FAU-alcohol pair can store as a function of the number of cations has been calculated. Use of the alcohol-MOF pairs as heat pumps or refrigerators. In this chapter, the possibility of using alcohols in different MOFs and ZIFs to transport heat from hot to cold environments is explored. By modifying the operating conditions of the adsorption and desorption cycles, a heat pump device can transport heat at convenience. All this is based on the principle that adsorption is an exothermic process. The high heat capacity of alcohols, their versatility and the ability to interact with both hydrophobic and hydrophilic structures make them great candidates for working fluids in devices such as heat pumps or refrigerators.
  • Publication
    Transferable Classical Force Field for Pure and Mixed Metal Halide Perovskites Parameterized from First-Principles
    (American Chemical Society, 2022-05-01) Seijas-Bellido, Juan Antonio; Samanta, Bipasa; Valadez-Villalobos, Karen; Gallardo, Juan Jesús; Navas, Javier; Balestra, Salvador; Madero Castro, Rafael María; Vicent-Luna, Jose Manuel; Tao, Shuxia; Caspary Toroker, Maytal; Anta, Juan A.
    Many key features in photovoltaic perovskites occur in relatively long time scales and involve mixed compositions. This requires realistic but also numerically simple models. In this work we present a transferable classical force field to describe the mixed hybrid perovskite MAxFA1¿xPb(BryI1¿y)3 for variable composition (¿x, y ¿ [0, 1]). The model includes Lennard-Jones and Buckingham potentials to describe the interactions between the atoms of the inorganic lattice and the organic molecule, and the AMBER model to describe intramolecular atomic interactions. Most of the parameters of the force field have been obtained by means of a genetic algorithm previously developed to parametrize the CsPb(BrxI1¿x)3 perovskite (Balestra et al. J. Mater. Chem. A. 2020, DOI: 10.1039/d0ta03200j). The algorithm finds the best parameter set that simultaneously fits the DFT energies obtained for several crystalline structures with moderate degrees of distortion with respect to the equilibrium configuration. The resulting model reproduces correctly the XRD patterns, the expansion of the lattice upon I/Br substitution, and the thermal expansion coefficients. We use the model to run classical molecular dynamics simulations with up to 8600 atoms and simulation times of up to 40 ns. From the simulations we have extracted the ion diffusion coefficient of the pure and mixed perovskites, presenting for the first time these values obtained by a fully dynamical method using a transferable model fitted to first-principles calculations. The values here reported can be considered as the theoretical upper limit, that is, without grain boundaries or other defects, for ion migration dynamics induced by halide vacancies in photovoltaic perovskite devices under operational conditions.