Articles publicats en revistes (Ciència dels Materials i Química Física)

URI permanent per a aquesta col·leccióhttps://hdl.handle.net/2445/9243

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Mechanically activated kaolin replacing metakaolin in alkali-activated cement formulation
(Taylor & Francis, 2025-12-01) Marco-Gibert, Josep; Alvarez-Coscojuela, Adrian; Mañosa Bover, Jofre; Formosa Mitjans, Joan; Chimenos Ribera, Josep Ma.
This work provides in-depth research on alkali-activated binder formulations, employing mechanically activatedkaolin (K-MA) as a substitute precursor for metakaolin (MK). The potential of K-MA to replace MK was evaluated byconducting an extensive characterization of the alkali-activated cements (AACs). The structural analysis performedthrough Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA),²⁷Aluminum magic angle spinning nuclear magnetic resonance (²⁷Al MAS NMR), and scanning electron microscopy(SEM) revealed that K-MA enhances the amorphous nature and microstructural homogeneity of cements. The resultsdemonstrated that K-MA-based cements exhibit superior compressive strength than MK-based cements, especiallywhen sodium silicate (waterglass) was added, achieving values up to 42 MPa at 28 days. These findings suggest thatK-MA is a highly effective precursor for AACs formulation, as well as an alternative to replace MK. While thermalactivation (TA) processes for dehydroxylation are associated with significant CO₂ emissions, mechanical activation(MA) offers a more sustainable alternative by utilizing electrical energy, which can be derived from less pollutingrenewable sources.
Interfacial behavior of binary, ternary and quaternary oil/water mixtures described from molecular dynamics simulations
(Elsevier B.V., 2021-02-15) Alonso Benito, Gerard; Gamallo Belmonte, Pablo; Rincón, Cristina; Sayós Ortega, Ramón
The correct description of crude oil/water interfaces is a very complex and an important task, particularly to the oil industry, whosemain difficulty relies on understanding how the interfacial properties (i.e., interfacial tension and interfacial accumulation) of the systemare affected by a very large number of components. To give some additional insight to the oil/water interfacial behavior, eleven oil/water mixtures (i.e., six binary, four ternary and a quaternary mixture) have been modeled through atomistic molecular dynamics simulations at laboratory conditions. All mixtures were built with a model oil based on dodecane, toluene, quinoline and a naphthenic acid, to represent the saturated, aromatic, basic resin and acid resin fractions, respectively. The results from this contribution show that interfacial tensions can be correlated to interfacial accumulation, which can be used as good starting point in predicting interfacial properties of oil mixtures. Additionally, the interfacial properties of mixtures behave similarly to the most polar pure oil/water interface, while all other compounds stay in the oil bulk as spectators. This behavior raises the question of whether using common n-alkane oils is a good enough approximation for modeling the interfacial properties of crude oils.
Limitations of free energy diagrams to predict the catalytic activity: the reverse water gas shift reaction catalyzed by Ni/TiC
(Academic Press, Elsevier, 2023) Lozano-Reis, Pablo; Prats Garcia, Hèctor; Sayós Ortega, Ramón; Illas i Riera, Francesc
The temporal evolution at the catalyst surface is a result of an intricate interplay between all involved microscopic events such as adsorption, desorption, diffusion, and bond breaking/formation steps, and the interaction with the surrounding environment. By properly including these effects, kinetic Monte Carlo (kMC) simulations can accurately describe the complexity of real catalysts, unravel the dominant reaction mechanisms and provide fundamental understanding towards the rational design of novel catalysts. In this work, we combine density functional theory (DFT) calculations, statistical thermodynamics and kMC simulations to study the reverse water–gas shift (RWGS) reaction on Ni/TiC, a bifunctional catalyst. The predictions from DFT energy profiles do not coincide with the outcome of the kMC simulations, evidencing the limitations of the former, especially in including the effect of coverage of surface species, which plays a crucial role. The kMC simulations results are in remarkable agreement with the experimental data, proving that the kMC simulations are able to describe the complex chemistry of the RWGS reaction on a bifunctional catalyst.
Multiscale study of the mechanism of catalytic CO₂ hydrogenation: role of the Ni(111) facets
(American Chemical Society, 2020-06-18) Lozano-Reis, Pablo; Prats Garcia, Hèctor; Gamallo Belmonte, Pablo; Illas i Riera, Francesc; Sayós Ortega, Ramón
The molecular mechanism of CO2 hydrogenation on a Ni(111) surface has been thoroughly investigated by means of periodic density functional theory calculations, including dispersion interactions, along with accurate kinetic Monte Carlo simulations, including lateral interactions between the adsorbates. The present reaction model involves 25 different species and a total of 86 elementary processes, including adsorptions, desorptions, surface chemical steps, and diffusions. The reaction network accounts for three different mechanisms for the reverse water-gas shift reaction and three different mechanisms for methanation. The kinetic Monte Carlo simulations reveal that the reverse water-gas shift reaction dominates the CO2 hydrogenation on Ni(111) with no evidence of methane formation. The reaction proceeds mainly through the redox route, with the carboxyl pathway also being active but to a lesser extent. Methane production is hindered by the H + CO → HCO endothermicity and the prohibitive energy barrier for CO dissociation, implying CO desorption rather than evolution through the Sabatier reaction. A detailed comparison to earlier theoretical studies supporting the methanation reaction shows that some unreliable assumptions along with limited theoretical approaches biased the former conclusion.
Highly Efficient Air Sterilization via Low-Temperature Interfacial Evaporation in Inductively Heated Superhydrophilic Ferromagnetic Filters
(Wiley-VCH Verlag, 2025-11-27) López-Ortega, A.; Garaio, E.; Esplandiu, María J.; Nogues, Josep; Sepúlveda, Borja; Fons, Arnau; Vaca, Cristina; Franco-Trepat, E.; Lafuente, Aritz; Tajada, J.L.; Serrà i Ramos, Albert; Diaz Pedroza, J.; Franco, S.; Boreika, R.; Erkizia, I.; Izquierdo Useros, Nuria
The scientific evidence supporting airborne transmission of pathogens in closed spaces highlights the inefficiency of current air circulation and filtration technologies (e.g., HEPA filters, UV, ozone, ionization) in preventing the spread of airborne pathogens. This underscores the urgent need for new air disinfection devices. Here, the first air sterilization technology is presented based on low-temperature interfacial evaporation. This novel approach integrates superhydrophilic micro/nano-structured stainless-steel filters and ultra-efficient magnetic inductive heating to enable complete evaporation of water from the contaminated aerosols and the precipitation of all the organic and inorganic residues within the filter at temperatures in the range of 60–80 °C. The technology is validated through experiments with contaminated aerosols with different active viruses, including SARS-CoV-2 and respiratory syncytial virus (RSV), demonstrating the elimination of 99.6% or more of the nebulized viruses, at filter temperatures of 60–80 °C and airflow rates of 15 L min⁻¹. The filters also support pyrolytic self-cleaning and reuse, ensuring extended service time and minimal maintenance. This air sterilization technology represents a significant advancement over existing state-of-the-art filtering technology, offering unmatched versatility, low energy consumption, and cost-effective sterilization, without generating harmful radicals, dangerous high voltages, or high temperatures.
Ion mobility–mass spectrometry of palytoxin-like compounds produced by Ostreopsis cf. ovata
(Springer Verlag, 2025-10-16) Medina Pérez, Noemí-Inmaculada; Peralta Moreno, María Nuria; Rubio Martínez, Jaime; Bechtella, Leïla; Polewski, Lukasz; Szekeres, Gergo Peter; Berdalet, Elisa; Moyano Morcillo, Encarnación; Pagel, Kevin
Palytoxin (PLTX) and its analogues from Ostreopsis cf. ovata are significant health concerns. They show potent vasoconstrictive properties, often causing seafood poisoning. PLTX analogues have chiral centers, resulting in many isomers, making their separation by liquid chromatography and identification/characterization by mass spectrometry challenging. This study explores for the first time the ion mobility spectrometry (IMS) behavior of these compounds to address these analytical challenges. Drift tube ion mobility spectrometry (DTIMS) and traveling wave ion mobility spectrometry (TWIMS) were used and compared. Additionally, trapped ion mobility spectrometry (TIMS) and molecular dynamics simulation were employed to explain unexpected results. TIMS provided higher resolution, distinguishing isomeric ions generated in the electrospray source by losing water molecules from different toxin sites. Computational studies offered theoretical insights into the ion mobility of triply charged calcium and sodium adduct ions, suggesting a folded conformation. DTCCSN2 (collisional cross section using DTIMS and nitrogen as buffer gas) values were obtained for PLTX (standard), ovatoxin-a, and ovatoxin-b from microalgae samples in Sant Andreu de Llavaneres (Barcelona, Spain). These values were comparable (ΔCCSs < 2%) to those measured with TWIMS calibrated using PLTX (standard). The study provides 102 CCS values from DTIMS and TWIMS data for adducts and fragment ions of PLTX analogues, which can be used as reference values in databases for toxin screening in complex samples.
On the role of dynamic electron correlation in non-orthogonal configuration interaction with fragments
(Royal Society of Chemistry, 2022) Sanchez-Mansilla, Aitor; Sousa Romero, Carmen; Kathir, R. K.; Broer, Ria; Straatsma, T. P.; de Graaf, Coen
Two different approaches have been implemented to include the effect of dynamic electron correlation in the Non-Orthogonal Configuration Interaction for Fragments (NOCI-F) method. The first is based on shifting the diagonal matrix elements of the NOCI matrix, while the second incorporates the dynamic correlation explicitly in the fragment wave functions used to construct the many-electron basis functions of the NOCI. The two approaches are illustrated for the calculation of the electronic coupling relevant in singlet fission and the coupling of spin moments in organic radicals. Comparison of the calculated diabatic couplings, the NOCI energies and wave functions shows that dynamic electron correlation is not only efficiently but also effectively incorporated by the shifting approach and can largely affect the coupling between electronic states. Also, it brings the NOCI coupling of the spin moments in close agreement with benchmark calculations.
Tuning MXenes Towards Their Use in Photocatalytic Water Splitting
(2024-06-27) Ontiveros Cruz, Diego; Vela Llausí, Sergi; Viñes Solana, Francesc; Sousa Romero, Carmen
Finding appropriate photocatalysts for solar-driven water (H2O) splitting to generate hydrogen (H2) fuel is a challenging task, particularly when guided by conventional trial-and-error experimental methods. Here, density functional theory (DFT) is used to explore the MXenes photocatalytic properties, an emerging family of two-dimensional (2D) transition metal carbides and nitrides with chemical formula Mn+1XnTx, known to be semiconductors when having Tx terminations. More than 4,000 MXene structures have been screened, considering different compositional (M, X, Tx, and n) and structural (stacking and termination position) factors, to find suitable MXenes with a bandgap in the visible region and band edges that align with the water-splitting half-reaction potentials. Results from bandgap analysis show how, in general, MXenes with n = 1 and transition metals from group III present the most cases with bandgap and promising sizes, with C-MXenes being superior to N-MXenes. From band alignment calculations of candidate systems with a bandgap larger than 1.23 eV, the minimum required for a water-splitting process, Sc2CT2, Y2CT2 (Tx = Cl, Br, S, and Se) and Y2CI2 are highlighted as adequate photocatalysts.
Exploring the photoactive properties of promising MXenes for water splitting
(Royal Society of Chemistry, 2024-11-19) Ontiveros Cruz, Diego; Viñes Solana, Francesc; Sousa Romero, Carmen
The photoactive properties and effectiveness of a selected group of ten terminated MXenes—Sc2CT2, Y2CT2 (T = Cl, Br, S, and Se), Y2CI2 and Zr2CO2—has been deeply studied by means of density functional theory (DFT). Here it is demonstrated that the studied MXenes exhibit robust energetic and dynamical stability, having all an indirect bandgap, while most of them with values within the visible spectrum, and also exhibiting suitable band alignment for the water splitting reaction. The charge density distribution of the valence band maximum (VBM) and conduction band minimum (CBM) is found to be separated across different layers with low overlaps, below 30%. Most MXenes present high charge carrier mobilities with favourable electron–hole disparities, with Sc2CBr2 also presenting directional charge carrier transport. Additionally, these materials show strong optical absorption (∼105 cm−1) in the visible spectrum, translating to promising solar-to-hydrogen (STH) efficiency theoretical limits, up to 23%. Overall, the combination of all these features positions MXenes among the optimal materials for efficient photocatalytic water splitting.
GronOR: Scalable and Accelerated Non-Orthogonal Configuration Interaction for Molecular Fragment Wave Functions
(American Chemical Society, 2022) Straatsma, T. P.; Broer, Ria; Sanchez-Mansilla, Aitor; Sousa Romero, Carmen; de Graaf, Coen
GronOR is a program package for nonorthogonalconfiguration interaction calculations. Electronic wave functions are constructed in terms of antisymmetrized products of multiconfiguration molecular fragment wave functions. The computational complexity of the nonorthogonal methodologies implemented in GronOR applied to large molecular assemblies requires a design that takes full advantage of massively parallel supercomputer architectures and accelerator technologies. This work describes the implementation strategy and resulting performance characteristics. In addition to parallelization and acceleration, the software development strategy includes aspects of fault resiliency and heterogeneous computing. The program was designed for large-scale supercomputers but also runs eﬀectively on small clusters and workstations for small molecular systems. GronOR is available as open source to the scientific community.
Understanding Kinetically Controlled Spin Transitions in Bistable Spin Crossover Materials
(Royal Society of Chemistry, 2023) Vela Llausí, Sergi; Fumanal Quintana, María; Sousa Romero, Carmen
Spin crossover (SCO) materials can be kinetically trapped in a photo-excited metastable state in the so-called LIESST and reverse-LIESST processes. Under these conditions, SCO molecules are excellent light-responsive bistable molecular switches. However, above a certain temperature (TLIESST and Tr-LIESST, respectively), the relaxation to the ground state becomes favorable and their bistability is suppressed. Understanding the mechanism of these processes, and being able to predict their kinetics, is key to designing SCO switches that are able to operate at room temperature. Herein, we reveal the mechanism of thermally induced spin transitions of the [FeII(1-bpp)2]2+ SCO complex, and we predict its TLIESST (as well as its T1/2) with unprecedented accuracy. This is possible here thanks to the efficient reconstruction of the low-spin (LS, S = 0), high-spin (HS, S = 2) and intermediate (IS, S = 1) state Free energy surfaces (FESs) with ab initio and machine-learning methods, and the characterization of the minimum energy crossing points (MECPs) connecting those FESs. This approach paves the way for the systematic investigation of molecular features determining the mechanism of kinetically controlled transitions in SCO materials, as well as their temperature-dependent rate constants.
A Lab-Scale Evaluation of Parameters Influencing the Mechanical Activation of Kaolin Using the Design of Experiments
(MDPI, 2024-09-01) Mañosa Bover, Jofre; Alvarez-Coscojuela, Adrian; Maldonado Alameda, Alex; Chimenos Ribera, Josep Ma.
This research investigates the mechanical activation of kaolin as a supplementary cementitious material at the laboratory scale, aiming to optimize milling parameters using the response surface methodology. The study evaluated the effects of rotation speed and milling time on the amorphous phase content, the reduction in crystalline kaolinite, and impurity incorporation into the activated clay through the Rietveld method. The results demonstrated that adjusting milling parameters effectively enhanced clay activation, which is crucial for its use in low-carbon cements. High rotation speeds (300/350 rpm) and prolonged grinding times (90/120 min) in a planetary ball mill increased the pozzolanic activity by boosting the formation of amorphous phases from kaolinite and illite and reducing the particle size. However, the results evidenced that intermediate milling parameters are sufficient for reaching substantial degrees of amorphization and pozzolanic activity, avoiding the need for intensive grinding. Exceedingly aggressive milling introduced impurities like ZrO2 from the milling equipment wear, underscoring the need for a balanced approach to optimizing reactivity while minimizing impurities, energy consumption, and equipment wear. Achieving this balance is essential for efficient mechanical activation, ensuring the prepared clay’s suitability as supplementary cementitious materials without excessive costs or compromised equipment integrity.
Light- and Redox-Dependent Force Spectroscopy Reveals that the Interaction between Plastocyanin and Plant Photosystem I Is Favored when One Partner Is Ready for Electron Transfer
(American Chemical Society, 2022-09-06) Zamora, Ricardo A.; López Ortiz, Manuel; Sales Mateo, Montserrat; Hu, Chen; Croce, Roberta; Abraham; Maniyara, Rinu Abraham; Rinu; Pruneri, Valerio; Giannotti, Marina Inés; Gorostiza, Pau
Charge exchange is the fundamental process that sustains cellular respiration and photosynthesis by shuttling electrons in a cascade of electron transfer (ET) steps between redox cofactors. While intraprotein charge exchange is well characterized in protein complexes bearing multiple redox sites, interprotein processes are less understood due to the lack of suitable experimental approaches and the dynamic nature of the interactions. Proteins constrained between electrodes are known to support electron transport (ETp) through the protein matrix even without redox cofactors, as the charges housed by redox sites in ET are furnished by the electrodes. However, it is unknown whether protein ETp mechanisms apply to the interprotein medium present in physiological conditions. We study interprotein charge exchange between plant photosystem I (PSI) and its soluble redox partner plastocyanin (Pc) and address the role of the Pc copper center. Using electrochemical scanning tunnelling spectroscopy (ECSTS) current-distance and blinking measurements, we respectively quantify the spatial span of charge exchange between individual Pc/PSI pairs and ETp through transient Pc/PSI complexes. Pc devoid of the redox center (Pcapo) can exchange charge with PSI at longer distances than with the copper ion (Pcholo). Conductance bursts associated to Pcapo/PSI complex formation are higher than in Pcholo/PSI. Thus, copper ions are not required for long distance Pc/PSI ETp but regulate its spatial span and conductance. Our results suggest that the redox center that carries the charge in Pc is not necessary to exchange it in interprotein ET through the aqueous solution, and question the canonical view of tight complex binding between redox protein partners.
MXgap: A MXene Learning Tool for Bandgap Prediction
(American Chemical Society, 2025-08-05) Ontiveros Cruz, Diego; Vela Llausí, Sergi; Viñes Solana, Francesc; Sousa Romero, Carmen
The increasing demand for clean and renewable energy has intensified the exploration of advanced materials for efficient photocatalysis, particularly for water splitting applications. Among these materials, MXenes, a family of two-dimensional (2D) transition metal carbides and nitrides, have shown great promise. This study leverages machine learning (ML) to address the resource-intensive process of predicting the bandgap of MXenes, which is critical for their photocatalytic performance. Using an extensive data set of 4356 MXene structures, we trained multiple ML models and developed a robust classifier-regressor pipeline that achieves a classification accuracy of 92% and a mean absolute error (MAE) of 0.17 eV for bandgap prediction. This framework, implemented in an open-source Python package, MXgap, has been applied to screen 396 La-based MXenes, identifying six promising candidates with suitable band alignments for water splitting whose optical properties were further explored via optical absorption and solar to-hydrogen (STH) efficiency. These findings demonstrate the potential of ML to accelerate MXene discovery and optimization for energy applications.
Thermal evaluation of polymorphic transitions in layered hybrid organic-inorganic perovskites for energy storage applications
(Elsevier, 2024-10-15) Salgado Pizarro, Rebeca; Navarro-Rivero, M. E.; Ding, Y.; Barreneche, Camila; Fernández Renna, Ana Inés
Layered hybrid organic-inorganic perovskites (LHOIPs) have gained specific attention in applications such as optoelectronics. However, from the thermal perspective, these materials present a high potential for thermal energy storage applications in solid-state due to their heat storage capacity during their phase transitions. Here, we evaluate the first-order transition of these materials from the molecular point of view and make a relation with organic size, which is responsible for the ordering-disordering transition. Six LHOIPs have been synthesised, (C12H25N)2CuCl4, (C14H29N)2CuCl4, (C16H33N)2CuCl4, (C12H24N)2MnCl4, (C14H29N)2MnCl4 and (C16H33N)2MnCl4, where the crystal transformation has been evaluated under X-ray diffraction and Raman, and thermal conductivity as well as the thermal expansion have been studied. This work provides a comprehensive evaluation of the disordering phenomenon that is produced during phase transitions
Reused and recycled. Archeometallurgical study of historical nails found in Guam, Mariana Islands, Western Pacific
(Elsevier, 2023-02-01) Salgado Pizarro, Rebeca; Camacho, Sara; Montón Subías, Sandra; Moragas Segura, Natàlia; Fernández Renna, Ana Inés
This article presents the results of the archaeometallurgical analyses (chemical, compositional, and mechanical) conducted on historic iron nails from the Marianas archipelago, in the western Pacific. The nails were recovered at the archaeological excavations of San Dionisio’s church and cemetery (Humåtak, Guam). They all came from abroad and were incorporated by the native communities through exchange, trade, or through the reuse of materials found in shipwrecks, although it is not possible at the moment to locate their exact origin. However, we know that all the analyzed samples had different metallographic and mechanical characteristics. This is the first study of these characteristics on Micronesia.
Enhancing reactivity in muscovitic clays: Mechanical activation as a sustainable alternative to thermal activation for cement production
(Elsevier B.V., 2024-01-24) Mañosa Bover, Jofre; Alvarez-Coscojuela, Adrian; Marco-Gibert, Josep; Maldonado Alameda, Alex; Chimenos Ribera, Josep Ma.
The use of calcined clays in the construction industry is thriving. However, muscovitic or illitic clays, which constitute a large portion of the available clay resources, are hardly activated by thermal processes. This work aims to enhance the reactivity of raw muscovitic clay through mechanical activation. Various combinations of milling time and rotation speed were evaluated. The results confirmed that a highly amorphous material was obtained through mechanical activation, while thermal activation led to muscovite dehydroxylation without inducing amorphisation, resulting in the formation of crystalline dehydroxylated muscovite. The reactivity of the activated clays as a potential precursor for cement production was assessed through pozzolanic activity measurements and Si and Al potential availability. Both confirmed that mechanically activated muscovitic clay presented significantly higher reactivity than calcined muscovitic clay, obtaining an excellent pozzolanic material or an alternative cement precursor. Accordingly, mechanical activation of muscovitic clays could effectively introduce these types of clay in the cement industry.
Life cycle assessment of the climate change impact of magnesium phosphate cements formulated with tundish deskulling waste compared to conventional cement
(Elsevier B.V., 2024-12-01) Alfocea Roig, Anna; Müller, Amelie; Steubing, Bernhard; Huete-Hernández, Sergio; Giró Paloma, Jessica; Formosa Mitjans, Joan
Ordinary Portland cement (OPC) production significantly contributes to greenhouse gas emissions due to high resource consumption and CO2 output. It is therefore imperative to investigate alternative cements, such as magnesium phosphate cement (MPC), as a potential solution. This study is based on Life Cycle Assessment (LCA) methodology, comparing OPC with alternative magnesium phosphate cements (MPC) developed at the laboratory scale. The novelty of this study considers two types of alternative cements that use two different sources of MgO: MPC-MgO, developed with pure MgO, and MPC-TUN, formulated using tundish deskulling waste from steelmaking industry. The evaluated functional units are 1 tonne of cement, 1 m3 of cement paste, and 1 m3 of mortar, all of them are designed for the same function, which is as non-structural precast elements. The study assesses climate change impacts under two future scenarios: 1) electricity decarbonisation in the background economy using projections from Integrated Assessment Models and 2) electricity decarbonisation and a fuel switch in the cement kilns. The results indicate that MPC-TUN exhibits a lower impact of climate change in terms of CO2 emissions across all functional units and scenarios compared to the other materials. In the most ambitious climate scenario, MPC-TUN mortar exhibits 42% and 56% lower climate change impacts than OPC-CEM I and MPC-MgO mortars, respectively, demonstrating its potential as a more sustainable construction material. Although further research is needed on the applicability of MPC-TUN in construction, regulatory frameworks are advised to simplify barriers to expedite the adoption of sustainable alternative cements.
New database of sustainable solid particle materials to perform a material-based design for a thermal energy storage in concentrating solar power
(Elsevier B.V., 2024-11-25) Majó, Marc; Calderón Díaz, Alejandro; Svobodova Sedlackova, Adela; Segarra Rubí, Mercè; Fernández Renna, Ana Inés; Barreneche, Camila
Renewable energies have surged worldwide, aiming to mitigate greenhouse gas emissions and reduce dependence on fossil fuels. Concentrated solar power (CSP) with thermal energy storage (TES) emerges as a viable alternative to bridge the gap between renewable energy generation and consumption. However, existing CSP plants face a significant challenge in optimizing performance due to the operational temperature limitations of solar salt. While alternative materials, such as solid particles for sensible heat storage in solar towers exceeding 600 °C, have been proposed, the crucial aspect revolves around selecting a new alternative sustainable low-cost material for use as a TES media. This article investigates the optimization of CSP-TES systems by evaluating alternative sustainable low-cost materials sourced from several sectors such as the mining or metallurgical industry, municipal solid wastes, or demolition wastes. The materials, either used in their original form or formulated into aggregates for mortars, underwent thorough a property comparison focused on thermal, physical properties, and cost. With this data, a database was created using the Constructor software from ANSYS and integrated with the Selector software from the same company that provides instrumental for the creation of a comprehensive repository of sustainable materials, providing a database that serves as a practical reference guide for optimizing the selection of sustainable materials as TES in CSP plants. Then, a baseline could be established for selecting a sustainable material for a specific design, considering the properties of the materials. This methodology consists of redesigning and adapting the system according to the material, and it is known as the Materials-Based Design (MBD) process.
Tuning electronic levels in photoactive hydroxylated titania nanosystems: combining the ligand dipole effect and quantum confinement
(Royal Society of Chemistry, 2024-12-01) Recio-Poo, Miguel; Morales García, Ángel; Illas i Riera, Francesc; Bromley, Stefan Thomas
Reducing the size of titania (TiO2) to the nanoscale promotes the photoactive anatase phase for use in a range of applications from industrial catalysis to environment remediation. The nanoscale dimensions of these systems affect the magnitude of the electronic energy gap by quantum confinement. Upon interaction with aqueous environments or water vapour, the surfaces of these systems will also be hydroxylated to some degree. In turn, this affects the electronic energy levels due to the cumulative electrostatic effect of the dipolar hydroxyl (–OH) ligands (i.e. the ligand dipole effect). Using accurate density functional calculations, we investigate the combined effects of quantum confinement and the hydration-induced ligand dipole effect on a set of realistic titania nanosystems over a wide range of hydroxylation. Our detailed investigation reveals that, contrary to previous models, the ligand dipole effect does not-linearly depend on the ligand coverage due to the formation of inter-ligand OH⋯OH hydrogen bonds. To account for the resulting effects, we propose a refined model, which describes the ligand dipole effect more accurately in our systems. We show that both hydroxylation (by the ligand dipole effect) and size (by quantum confinement) have significant but distinct impacts on the electronic energy levels in nanotitania. As an example, we discuss how variations in these effects can be used to tune the highest unoccupied energy level in nanotitania for enhancing the efficiency of the hydrogen evolution reaction. Overall, we show that any specific energy shift can be achieved by a range of different combinations of nanosystem size and degree of hydroxylation, thus providing options for energy-level tuning while also allowing consideration of practical constraints (e.g. synthetic limitations, operating conditions) for photochemical applications.

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