| 1. |
- Chavez-Caiza, J., et al.
(författare)
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Unveiling the effect of sacrificial agent amount in the CO2 photoreduction performed in a flow reactor
- 2024
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Ingår i: Journal of CO2 Utilization. - : Elsevier BV. - 2212-9820 .- 2212-9839. ; 83
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Tidskriftsartikel (refereegranskat)abstract
- The use of sacrificial agents in photocatalysis is a powerful resource to enhance the performance of photoactive materials. Despite its importance, the effect of the amount of sacrificial agent is not properly described in the literature. In this paper, we have focused on the role of EtOH in the photoreduction of CO2 to CH4 using Cu-P25 photocatalysts in a flow reactor. We found that the production of CH4 increased with the concentration of EtOH, achieving an outstanding CH4 production yield of 235 mu mol/(g & sdot;h) for a flow of 0.25 mu mol/min of EtOH in the gas stream, hinting at the important role of the sacrificial agent in the reaction. The catalytic results together with the characterization of the materials highlight the need to achieve a minimum surface coverage of EtOH on the surface of the catalyst to control the reaction pathway. The adsorption of EtOH is a key factor in boosting the catalytic activity of the best-performing catalyst and producing CH4 from CO2 photoreduction and C2H4O from the photooxidation of EtOH, obtaining two easily separable interesting products for industrial applications in one reaction.
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| 2. |
- Lousada, Cláudio M., 1978-, et al.
(författare)
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Experimental and Molecular Dynamics Simulation Study of the Sublimation and Vaporization Energetics of Iron Metalocenes. Crystal Structures of Fe(η5-C5H4CH3)2 andFe[(η5-(C5H5)(η5-C5H4CHO)]
- 2008
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 112, s. 2977-2987
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Tidskriftsartikel (refereegranskat)abstract
- The standard molar enthalpies of sublimation of ferrocene, 1,1'-dimethylferrocene, decamethylferrocene, ferrocenecarboxaldehyde and R-methylferrocenemethanol, and the enthalpy of vaporization of N,N-dimethyl-(aminomethyl)ferrocene, at 298.15 K, were determined by Calvet-drop microcalorimetry and/or the Knudsen effusion method. The obtained values were used to assess and refine our previously developed force field for metallocenes. The modified force field was able to reproduce the ΔsubH°m and ΔvapH°m values of the test-set with an accuracy better than 5 kJ·mol-1, except for decamethylferrocene, in which case the deviation between the calculated and experimental ΔsubH°m values was 16.1 kJ·mol-1. The origin of the larger error found in the prediction of the sublimation energetics of decamethylferrocene, and which was also observed in the estimation of structural properties (e.g., density and unit cell dimensions), is discussed. Finally, the crystal structures of Fe(η5-C5H4CH3)2 and Fe[(η5-(C5H5)(η5-C5H4CHO)] at 293 and 150 K, respectively, are reported.
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| 3. |
- Lousada, Cláudio M., et al.
(författare)
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Synthesis of copper hydride (CuH) from CuCO3·Cu(OH)2 – a path to electrically conductive thin films of Cu
- 2017
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 46:20, s. 6533-6543
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Tidskriftsartikel (refereegranskat)abstract
- The most common synthesis methods for copper hydride (CuH) employ hard ligands that lead to the formation of considerable amounts of metallic Cu as side-product. Here we explore a synthesis method for CuH(s) through the reaction of CuCO3 center dot Cu(OH)(2)(s) with hypophosphorous acid (H3PO2) in solution, via the formation of the intermediate Cu(H2PO2)(2)(aq) complex. The reaction products were characterized with XRD, FTIR and SEM at different reaction times, and the kinetics of the transformation of Cu(H2PO2)(2)(aq) to CuH(s) were followed with NMR and are discussed. We show that our synthesis method provides a simple way for obtaining large amounts of CuH(s) even when the synthesis is performed in air. Compared to the classic Wurtz method, where CuSO4 is used as an initial source of Cu2+, our synthesis produces CuH particles with less metallic Cu side-product. We attribute this to the fact that our reaction medium is free from the hard SO42- ligand that can disproportionate Cu(I). We discuss a mechanism for the reaction based on the known reactivity of the reagents and intermediates involved. We explored the possibility of using CuH(s) for making electrically conductive films. Tests that employed water-dispersed CuH particles show that this compound can be reduced with H3PO2 leading to electrically conductive thin films of Cu. These films were made on regular office paper and were found to be Ohmic conductors even after several weeks of exposure to ambient conditions. The fact that the synthesis reported here produces large amounts of CuH particles in aqueous media, with very little impurities, and the fact that these can then be converted to a stable electrically conductive film can open up new applications for CuH such as for printing electrically conductive films or manufacturing surface coatings.
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| 4. |
- Gertz, Morie, et al.
(författare)
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Avoiding misdiagnosis : expert consensus recommendations for the suspicion and diagnosis of transthyretin amyloidosis for the general practitioner
- 2020
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Ingår i: BMC Family Practice. - : BMC. - 1471-2296. ; 21:1
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Tidskriftsartikel (refereegranskat)abstract
- Background Transthyretin amyloidosis (also known as ATTR amyloidosis) is a systemic, life-threatening disease characterized by transthyretin (TTR) fibril deposition in organs and tissue. A definitive diagnosis of ATTR amyloidosis is often a challenge, in large part because of its heterogeneous presentation. Although ATTR amyloidosis was previously considered untreatable, disease-modifying therapies for the treatment of this disease have recently become available. This article aims to raise awareness of the initial symptoms of ATTR amyloidosis among general practitioners to facilitate identification of a patient with suspicious signs and symptoms. Methods These consensus recommendations for the suspicion and diagnosis of ATTR amyloidosis were developed through a series of development and review cycles by an international working group comprising key amyloidosis specialists. This working group met to discuss the barriers to early and accurate diagnosis of ATTR amyloidosis and develop a consensus recommendation through a thorough search of the literature performed using PubMed Central. Results The cardiac and peripheral nervous systems are most frequently involved in ATTR amyloidosis; however, many patients often also experience gastrointestinal and other systemic manifestations. Given the multisystemic nature of symptoms, ATTR amyloidosis is often misdiagnosed as a more common disorder, leading to significant delays in the initiation of treatment. Although histologic evaluation has been the gold standard to confirm ATTR amyloidosis, a range of tools are available that can facilitate early and accurate diagnosis. Of importance, genetic testing should be considered early in the evaluation of a patient with unexplained peripheral neuropathy. Conclusions A diagnostic algorithm based on initial red flag symptoms and manifestations of cardiac or neurologic involvement will facilitate identification by the general practitioner of a patient with clinically suspicious symptoms, enabling subsequent referral of the patient to a multidisciplinary specialized medical center.
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| 5. |
- Ghadami Yazdi, Milad, et al.
(författare)
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Structure dependent effect of silicon on the oxidation of Al(111) and Al(100)
- 2019
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Ingår i: Surface Science. - : Elsevier. - 0039-6028 .- 1879-2758. ; 684, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- The effect of sub-monolayer silicon on the oxidation of Al(111) and Al(100) surfaces was investigated using X-ray Photoelectron Spectroscopy (XPS) and density functional theory (DFT) calculations. On both surfaces the adatom site is preferred over substituting Si into the Al-lattice; on Al(100) the four fold hollow site is vastly favored whereas on Al(111) bridge and hollow sites are almost equal in energy. Upon O 2 exposure, Si is not oxidized but buried at the metal/oxide interface under the growing aluminum oxide. On Al(111), Si has a catalytic effect on both the initial oxidation by aiding in creating a higher local oxygen coverage in the early stages of oxidation and, in particular, at higher oxide coverages by facilitating lifting Al from the metal into the oxide. The final oxide, as measured from the Al2p intensity, is 25–30% thicker with Si than without. This observation is valid for both 0.1 monolayer (ML) and 0.3 ML Si coverage. On Al(100), on the other hand, at 0.16 ML Si coverage, the initial oxidation is faster than for the bare surface due to Si island edges being active in the oxide growth. At 0.5 ML Si coverage the oxidation is slower, as the islands coalesce and he amount of edges reduces. Upon oxide formation the effect of Si vanishes as it is overgrown by Al 2 O 3 , and the oxide thickness is only 6% higher than on bare Al(100), for both Si coverages studied. Our findings indicate that, in addition to a vanishing oxygen adsorption energy and Mott potential, a detailed picture of atom exchange and transport at the metal/oxide interface has to be taken into account to explain the limiting oxide thickness.
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| 6. |
- Korzhavyi, Pavel A., 1966-, et al.
(författare)
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Exploring configurational degrees of freedom in disordered solids
- 2018
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Ingår i: International Conference of Computational Methods in Sciences and Engineering 2018 (ICCMSE 2018). - : American Institute of Physics (AIP). - 9780735417663
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Konferensbidrag (refereegranskat)abstract
- Recent computational modeling studies of configurational degrees of freedom in oxide-hydroxides of aluminum and copper are reviewed. Density functional theory calculations are employed to investigate the effect of hydrogen on the structural stability of gamma-alumina and to explore the configurational space of cuprous hydroxide CuOH. Free energy modeling, taking into account configurational and vibrational degrees of freedom, shows that the studied hydrogenated oxides of aluminum and copper are metastable compounds, whereas the respective oxides are thermodynamically stable phases. Selected structural and optical properties of the studied compounds, evaluated using a hybrid functional approach, are reported and compared with available experimental data.
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| 7. |
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| 8. |
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| 9. |
- Lousada, Claudio M., et al.
(författare)
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Adsorption of Hydrogen Sulfide, Hydrosulfide and Sulfide at Cu(110) - Polarizability and Cooperativity Effects. First Stages of Formation of a Sulfide Layer
- 2018
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Ingår i: ChemPhysChem. - : Wiley-VCH Verlag. - 1439-4235 .- 1439-7641. ; 19:17, s. 2159-2168
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the surface site preference for single adsorbates, the interactions between adsorbates, how these interactions affect surface site specificity in adsorption and perturb the electronic states of surfaces is important for rationalizing the structure of interfaces and the growth of surface products. Herein, using density functional theory (DFT) calculations, we investigated the adsorption of H2S, HS and, S onto Cu(110). The surface site specificity observed for single adsorbates can be largely affected by the presence of other adsorbates, especially S that can affect the adsorption of other species even at distances of 13 Å. The large supercell employed with a surface periodicity of (6×6) allowed us to safely use the Helmholtz method for the determination of the dipole of the surface-adsorbate complex at low adsorbate coverages. We found that the surface perturbation induced by S can be explained by the charge transfer model, H2S leads to a perturbation of the surface that arises mostly from Pauli exclusion effects, whereas HS shows a mix of charge transfer and Pauli exclusion effects. These effects have a large contribution to the long range adsorbate-adsorbate interactions observed. Further support for the long range adsorbate-adsorbate interactions are the values of the adsorption energies of adsorbate pairs that are larger than the sum of the adsorption energies of the single adsorbates that constitute the pair. This happens even for large distances and thus goes beyond the H-bond contribution for the H-bond capable adsorbate pairs. Exploiting this knowledge we investigated two models for describing the first stages of growth of a layer of S-atoms at the surface: the formation of islands versus the formation of more homogeneous surface distributions of S-atoms. We found that for coverages lower than 0.5 ML the S-atoms prefer to cluster as islands that evolve to stripes along the [1 (Formula presented.) 0] direction with increasing coverage. At 0.5 ML a homogeneous distribution of S-atoms becomes more stable than the formation of stripes. For the coverage equivalent to 1 ML, the formation of two half-monolayers of S-atoms that disrupt the Cu−Cu bonds between the first and second layer is more favorable than the formation of 1 ML homogeneous coverage of S-atoms. Here the S−Cu bond distances and geometries are reminiscent of pyrite, covellite, and to some extent chalcocite. The small energy difference of ≈0.1 eV that exists between this structure and the formation of 1 ML suggests that in a real system at finite temperature both structures may coexist leading to a structure with even lower symmetry.
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| 10. |
- Lousada, Claudio M., et al.
(författare)
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Application of reactivity descriptors to the catalytic decomposition of hydrogen peroxide at oxide surfaces
- 2015
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Ingår i: Computational and Theoretical Chemistry. - : Elsevier. - 2210-271X .- 2210-2728. ; 1070, s. 108-116
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Tidskriftsartikel (refereegranskat)abstract
- We have employed density functional theory (DFT) calculations using the PBE0 functional to study the reaction of decomposition of H2O2 on clusters of: ZrO2, TiO2, Y2O3, Fe2O3, CeO2, CuO, Al2O3, NiO2, PdO2 and Gd2O3. The formation of the products of decomposition of H2O2 and their binding onto these oxides are discussed. The obtained energy barriers for H2O2 decomposition deviate from experimental data in absolute average by 4 kJ mol(-1). The only exceptions are CeO2 and Fe2O3 for which the deviations are very large. The adsorption of HO radicals onto the clusters was also studied. Reactivity descriptors obtained with DFT calculations are correlated with experimental data from literature. We found a direct correlation between the adsorption energy of HO radicals and the change in Mulliken charge of the cation present in the oxide, upon adsorption of these radicals. Other DFT and experimentally obtained reactivity descriptors based on properties of the cations present in the oxides, such as the ionization potential and electronegativity are plotted against experimental and DFT computed properties, respectively. Following the Bronsted-Evans Polanyi principle, there is a correlation between the adsorption energy of the product HO radical and the energy barrier for decomposition of H2O2. The good correlations between experimental data and the data obtained with DFF using minimalistic cluster models of the oxides surfaces indicates that on the real systems the processes that determine the reactivity of H2O2 are very dependent on localized properties of the surfaces.
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