Study of Ceria-based materials and their application in electrochemical and gas-phase catalysis

This thesis is focused on the preparation of nanostructured ceria catalysts with an electrochemical approach and on their use in reactions relevant to environmental issues, like CO2 electrochemical reduction and low temperature catalytic combustion, in the gas phase. Supports with totally different compositions and geometries were used for the preparation of electrocatalysts and gas-phase catalysts, but in all cases ceria was cathodically deposited via an electroprecipitation process triggered by local pH increase. To study CO2 reduction, ceria was cathodically deposited on boron-doped diamond, obtaining control of its morphology and composition, both crucial aspect in ceria catalytic applications. Promising efficiency toward formate production was demonstrated, at very low overpotential. To produce catalysts for low-temperature combustion of methanol and CO oxidation, platinum and ceria were sequentially deposited onto Fecralloy 3D foams, the support currently used in industrial structured catalysts. To extend the scope of the studies on CO2 reduction, copper oxide graphenide materials were investigated and compared to ceria. These materials were shown to effectively reduce CO2 to formate, exhibiting good stability and resistance to poisoning. Their performance matched those of the best catalysts described in the literature

The HER in alkaline media on Pt-modified three-dimensional Ni cathodes

[EN] Electrodeposited porous Ni layers and commercial Ni foams were submitted to spontaneous deposition of Pt, achieved by immersing the Ni substrates in H2PtCl6 solutions, at open circuit, to produce Pt-modified 3D Ni electrodes. When using Ni foams, the immersion was prolonged until the whole amount of H2PtCl6 in the solution had reacted. Such an approach, which granted an easy control of the Pt loading, could not be used for Ni trodeposits, since they underwent significant corrosion. The true Pt surface area was determined by measuring, for each electrode, the hydrogen desorption charge according to methods described in the literature. The ratios between Pt surface area and Pt loading were higher for Ni foam electrodes than for porous Ni electrodeposits. Both kinds of Pt-modified Ni electrodes were used as cathodes for hydrogen evolution in 1 M KOH. Cathodes with Pt loading below 0.5 mg cm(-2) (referred to geometric surface area) evolved hydrogen at -100 mA cm(-2) with a -75 mV overpotential. The better activity of foam electrodes as compared to electrodeposits, especially at low Pt loading, was mainly due to their higher Pt surface area per unit Pt mass. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.The authors from IENI-CNR acknowledge the financial support of the Italian Ministry for Economic Development (MSE) - MSE-CNR Agreement on National Electrical System. I. Herraiz-Cardona is grateful to the Ministerio de Educacion of Spain for a post-graduate grant (Ref. AP2007-03737). The authors are indebted to Dr. Arianna Gambirasi, ICIS CNR, Padova, Italy for recording SEM images and to FILA INDUSTRIA CHIMICA SPA, San Martino di Lupari, Padova, Italy, owner of the Fei-ESem FEI Quanta 200 FEG instrument, for allowing its use for the research work described in this article.Fiameni, S.; Herraiz Cardona, I.; Musiani, M.; Pérez-Herranz, V.; Vázquez-Gómez, L.; Verlato, E. (2012). The HER in alkaline media on Pt-modified three-dimensional Ni cathodes. International Journal of Hydrogen Energy. 37(14):10507-10516. https://doi.org/10.1016/j.ijhydene.2012.04.100S1050710516371

Oxide-oxide galvanic displacement reactions: Effect of the concentration of the ions released by the sacrificial oxide

Abstract Galvanic displacement reactions between a solid oxide and a dissolved metal cation are interesting processes for the preparation of oxide nanoparticles or electrocatalytic layers consisting of secondary mixed oxides. Their mechanism is not yet fully clarified. The composition of the secondary mixed oxides and their growth rate depend on many physical and chemical variables. In the present study, we have focused on the effects of the concentration of the ions released from the sacrificial oxide to the solution, when they are intentionally added to reaction media. We have studied the displacement of sacrificial PbO2 by either Mn2+ or Co2+ cations in acetate solution that contained variable concentrations of Pb2+, using electrochemical methods, SEM-EDS and XPS. The evolution of the open circuit potential of the systems was monitored during the reactions. We have found that, for both divalent cations, increasing concentrations of Pb2+ ions in the acetate solutions caused the formation of mixed oxides richer in Pb. Effects on growth rate and equilibrium potential were different for Mn2+ and Co2+

Incidence and Determinants of Symptomatic and Asymptomatic SARS-CoV-2 Breakthrough Infections After Booster Dose in a Large European Multicentric Cohort of Health Workers-ORCHESTRA Project

Background: SARS-CoV-2 breakthrough infections (BI) after vaccine booster dose are a relevant public health issue. Methods: Multicentric longitudinal cohort study within the ORCHESTRA project, involving 63,516 health workers (HW) from 14 European settings. The study investigated the cumulative incidence of SARS-CoV-2 BI after booster dose and its correlation with age, sex, job title, previous infection, and time since third dose. Results: 13,093 (20.6%) BI were observed. The cumulative incidence of BI was higher in women and in HW aged < 50 years, but nearly halved after 60 years. Nurses experienced the highest BI incidence, and administrative staff experienced the lowest. The BI incidence was higher in immunosuppressed HW (28.6%) vs others (24.9%). When controlling for gender, age, job title and infection before booster, heterologous vaccination reduced BI incidence with respect to the BNT162b2 mRNA vaccine [Odds Ratio (OR) 0.69, 95% CI 0.63-0.76]. Previous infection protected against asymptomatic infection [Relative Risk Ratio (RRR) of recent infection vs no infection 0.53, 95% CI 0.23-1.20] and even more against symptomatic infections [RRR 0.11, 95% CI 0.05-0.25]. Symptomatic infections increased from 70.5% in HW receiving the booster dose since < 64 days to 86.2% when time elapsed was > 130 days. Conclusions: The risk of BI after booster is significantly reduced by previous infection, heterologous vaccination, and older ages. Immunosuppression is relevant for increased BI incidence. Time elapsed from booster affects BI severity, confirming the public health usefulness of booster. Further research should focus on BI trend after 4th dose and its relationship with time variables across the epidemics.BackgroundSARS-CoV-2 breakthrough infections (BI) after vaccine booster dose are a relevant public health issue.MethodsMulticentric longitudinal cohort study within the ORCHESTRA project, involving 63,516 health workers (HW) from 14 European settings. The study investigated the cumulative incidence of SARS-CoV-2 BI after booster dose and its correlation with age, sex, job title, previous infection, and time since third dose.Results13,093 (20.6%) BI were observed. The cumulative incidence of BI was higher in women and in HW aged < 50 years, but nearly halved after 60 years. Nurses experienced the highest BI incidence, and administrative staff experienced the lowest. The BI incidence was higher in immunosuppressed HW (28.6%) vs others (24.9%). When controlling for gender, age, job title and infection before booster, heterologous vaccination reduced BI incidence with respect to the BNT162b2 mRNA vaccine [Odds Ratio (OR) 0.69, 95% CI 0.63-0.76]. Previous infection protected against asymptomatic infection [Relative Risk Ratio (RRR) of recent infection vs no infection 0.53, 95% CI 0.23-1.20] and even more against symptomatic infections [RRR 0.11, 95% CI 0.05-0.25]. Symptomatic infections increased from 70.5% in HW receiving the booster dose since < 64 days to 86.2% when time elapsed was > 130 days.ConclusionsThe risk of BI after booster is significantly reduced by previous infection, heterologous vaccination, and older ages. Immunosuppression is relevant for increased BI incidence. Time elapsed from booster affects BI severity, confirming the public health usefulness of booster. Further research should focus on BI trend after 4th dose and its relationship with time variables across the epidemics

SARS-CoV-2 Breakthrough Infections: Incidence and Risk Factors in a Large European Multicentric Cohort of Health Workers

The research aimed to investigate the incidence of SARS-CoV-2 breakthrough infections and their determinants in a large European cohort of more than 60,000 health workers

Magnetic forces for surface-based bioanalysis in microfluidic devices

Biochemical analysis is a critical part of clinical diagnostics, forensic science and environmental monitoring. Typically, this form of analysis involves the use of bioanalytical procedures which are extremely sensitive and highly specific. However, such assays often involve many different reaction and washing steps, which means that a single analysis could take hours or even days to perform. There is an urgent demand for high through-put analysis systems that are rapid, simple to use and can be utilised in the field or at the point-of-care. Microfluidic technology has gone some way to producing such systems, however many of the current devices still incorporate batch methods of analysis, which are still time consuming or do not integrate all steps of the analysis on one device. Two aspects of particle handling utilising magnetic forces were investigated. 1) The use of single magnetic particles as mobile solid-supports in a continuous flow system for bioanalysis. 2) The use of diamagnetic repulsion forces for label-free on-chip particle handling. For the continuous flow system, a magnetic particle type was selected from eight commercially available brands of particles and characterised using on and off-chip measurements. Dynabead M-270 particles were ultimately used as mobile solidsupports for performing entire bioanalytical processes in continuous flow, for the first time. This was achieved by generating multiple laminar flow streams along the length of a rectangular chamber and applying a magnetic field gradient perpendicular to flow. Each reagent stream contained reagents for a molecular binding assay and functionalised magnetic particles were deflected across the width of the chamber. As the particles were deflected through reagent streams, washing and reaction steps were performed on the surface of the particle in one operation in continuous flow. The system was used to perform a one-step streptavidin - biotin binding assay with an LOD of 20 µg mL-1 , a two-step mouse IgG immunoassay with an LOD of 0.1 µg mL-1 and a qualitative sandwich immunoassay for C-reactive protein (CRP). All three procedures were performed within one minute with no manual intervention. For the diamagnetic repulsion forces for label-free particle handling, 10 µm polystyrene particles were trapped into plugs on a glass capillary by suspending them in a paramagnetic solution and creating an area of high magnetic field gradient between two magnets. Particles were repelled by the field and formed a plug upstream from the magnets. The system was used to simultaneously perform positive and negative controls on a sample of fluorescently labelled biotin using two plugs; one containing streptavidin functionalised polystyrene particles and one containing plain polystyrene particles. In addition, diamagnetic repulsion was used to deflect polystyrene particles from flow inside a square deflection chamber. A particle mixture of 5 µm and 10 µm particles were separated into different exits at a flow rate of 20 µLh-1 based on the difference in their volume, termed free-flow diamagnetophoresis. Potential applications include label-free cell manipulation.EThOS - Electronic Theses Online ServiceUniversity of HullEngineering and Physical Sciences Research CouncilGBUnited Kingdo

Combined IP/OOP parametric non-linear static analysis on RC frame buildings infilled with strengthened thin masonry panels

The use of unreinforced thin clay masonry infills in RC frames as internal partition walls is widespread. Medium and more severe earthquakes are responsible of relevant monetary and human life losses caused by the interaction between the In-Plane and the Out-Of-Plane action that affects these non-structural elements. In order to reduce the Out-Of-Plane vulnerability of these weak panels, three external reinforcing solutions were experimentally investigated at the laboratory of the University of Padova. Such solutions consists of external plaster layers applied both sides of the masonry wall and the additional embedding of a basalt fiber mesh. This paper presents a new macro-model able to predict the combined In-Plane/Out-Of-Plane response of thin masonry infills through two non-linear fiber struts along each diagonal direction. The proposed macro-model was calibrated on the results of combined In-Plane/Out-Of-Plane experimental tests carried out on unreinforced and strengthened thin masonry infills. The aim of the numerical study is the evaluation of the benefits of the proposed reinforcing solutions on the RC infilled frames overall behavior. For this purpose, an extended parametric non-linear static analysis was carried out on RC frames representative of the Italian building stock, both traditionally and seismically designed. Two different incremental In-Plane force patterns were applied on the frame whereas Out-of-Plane equivalent static forces, calculated for three increasing values of Peak Ground Acceleration, were applied directly on the nonstructural elements. The analyses were carried out for both types of panels previously calibrated. The evaluation of the strengthening effectiveness is shown in terms of improvement of the overall structural response, postponement of all infill Limit States and thus different damage distribution along building height. Finally, the new Italian Seismic Classification procedure was implemented to evaluate the reduction of the expected annual seismic losses, as well as of the seismic Risk Class

Direct electrodeposition of metal nanowires on electrode surface

A method for decorating the surface of disk electrodes with metal nanowires is presented. Cu and Ni nanowires with diameters from 1.0 m to 0.2 m are directly deposited on the electrode surface using a polycarbonate membrane filter template maintained in contact with the metal substrate by the soft homogeneous pressure of a sponge soaked with electrolyte. The morphologic and structural properties of the deposit are characterized by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The latter shows that the head of nanowires with diameter of 0.4 m is ordinarily polycrystalline, and that of nanowires with diameter of 0.2 m is almost always monocrystalline for Cu and frequently also for Ni. Cyclic voltammetries and impedance investigations recorded in alkaline solutions at representative Ni electrodes decorated with nanowires provide consistent values of roughness factor, in the range 20–25