1,291 research outputs found
Among old materials and different approaches to enhance stability and electrochemical activity of Solid Oxide Cells
No full textPerovskite materials are widely studied as cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFC) for their relevant properties regarding electrocatalytic activity or stability. Nevertheless, a material that combines both it is not yet available. Among them, La1-XSrxMnO3 (LSM), La1-xSrxCo1-yFeyO3 (LSCF), Ba1-xSrxCo1-yFeyO3 (BSCF), La1-xSrxFeO3 (LSF), La1-xBaxCoO3 (LBC), were deeply investigated but their properties are not completely exploited or optimized.
In this PhD project all the reported electrode materials are investigated using different approaches. The study starts from LSM – based electrodes, which show a change in kinetic mechanism under particular operating conditions. These results open new horizons about the employment of this material, up today considered not suitable for IT-SOFC temperature range. A first application, with promising results, is proposed here with a LSM infiltration in LSCF and BSCF scaffold. The presence of infiltrated-phase enhance stability and electrochemical activity of electrodes.
Promising results are obtained also by mixing BSCF and LSCF powders. Three different BSCF:LSCF ratio are considered to produce three different cathodes. All the new compositions show an improvement of activity for oxygen reduction reaction, with very competitive values of polarization resistance. Moreover, one of these new electrodes has also a lowering of degradation rate compared with reference materials
In the last year of this project, other two materials are combined and their interactions investigate. LSF, providing a high stability, is coupled with LBC, which has a really high surface electrocatalytic activity. The two materials are tested in different thin film systems. When they are mixed before the sintering stage react forming a new perovskite phase (Ba0.099Sr0.297La0.594Fe0.8Co0.2O3), with a higher activity. The reaction is avoided producing a bilayer system, and the presence of LBC top layer over a LSF dense thin film drastically reduces polarization resistance, highlighting promising results
Microstructural and electrochemical properties of Ni-impregnated GDC10 and 8YSZ freeze tape cast scaffolds as fuel electrodes for solid oxide cells
No full textElectrochemical technologies for wastewater treatment at pilot plant scale
No full textProcess scale-up is a critical, but essential, step in the development of real electrochemical system for
oxidation of organic compound. This mini review wants critically analyze the research efforts carried out in the last years about pre-pilot and pilot scale plants, to support the implementation of such
technologies in industrial environmental. In the first section are presented the potentiality and the
issues related to the anodic oxidation. The second part is dedicated to the electro-Fenton process,
while the last is focused on the coupling of the two previous methods. The analysis highlights key
factors which are involved in the scaling-up, which are concerning not only the plant size, but
involved also their efficiency and economic feasibility
Tra vecchi materiali e diversi approcci per migliorare la stabilità e l’attività elettrochimica delle cella ad ossido solido
No full textLe celle ad ossidi solidi (SOC), siano esse celle combustibili (SOFC) o elettrolizzatori (SOEC), sono una tecnologia in grado di fornire risposte concrete alla rivoluzione energetica attualmente in corso. Tuttavia perché i loro indiscussi vantaggi, quali il ridotto impatto ambientale, la flessibilità al carico e la modularità, diventino competitivi con le tecnologie maggiormente consolidate sul mercato, è ancora necessario un ulteriore sforzo riguardo la loro durata nel tempo. Infatti alle alte temperature d’esercizio (~ 800 °C) di questi sistemi corrisponde un degrado del materiale e una perdita in performance. La via maestra per limitare questo effetto indesiderato è la riduzione della temperatura (500-700 °C); questo approccio ha come possibile conseguenza la perdita di prestazione da parte dei materiali maggiormente impiegati a temperature superiori. In particolar modo le performance e la stabilità del catodo, sede della reazione di riduzione dell’ossigeno, sono molto sensibili a questo parametro, influenzando il comportamento globale della cella. Questo scenario richiede quindi lo sviluppo di materiali stabili in grado di fornire un’attività elettrochimica performante alle temperature target della ricerca attuale. Negli ultimi anni le perovskiti (ABO3) sono una classe di materiali che si è dimostrata promettente per raggiungere questo obiettivo. Tra questi, i materiali più studiati sono La0.8Sr0.2MnO3 (LSM), La0.6Sr0.4Co0.2Fe0.8O3-δ(LSCF), Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF). I risultati riportati in letteratura hanno dimostrato come sia difficile combinare prestazione elettrochimica e durata nel tempo, e come questi soffrano o di scarse performance (LSM) o problemi di degrado non trascurabili (LSCF, BSCF). Questa tesi è nata quindi nel tentativo di investigare se mediante diversi approcci disponibili per la preparazione dell’elettrodo (infiltrazione, elettrodo composito), fosse possibile migliorare le caratteristiche richieste per un materiale catodico.
Lo studio è partito investigando il comportamento elettrochimico di elettrodi a base di LSM, un materiale considerato principalmente come conduttore elettronico. I risultati ottenuti hanno mostrato un cambiamento nel meccanismo cinetico, in funzione del sovrapotenziale applicato alla cella. Tali risultati, aprono nuovi orizzonti riguardo lo sfruttamento di questo materiale, fino ad oggi considerato non adatto per l’impiego in sistemi SOFC a temperature intermedie (IT-SOFC). Una prima applicazione, con promettenti risultati, è stata fornita eseguendo l’infiltrazione di nanoparticelle di LSM su scaffold di altri due materiali perovskitici, quali LSCF e BSCF. La presenza di queste particelle sulla superficie elettrodica ha avuto come conseguenza quella di incrementare sia stabilità che performance elettrochimica dei due materiali di partenza. Il secondo step del progetto ha considerato un elettrodo composito, costituito da un mixing di due materiali, LSCF e BSCF. Entrambi i materiali forniscono eccellenti proprietà elettrocatalitiche, ma soffrono di una certa instabilità ed elevato degrado. Con l’idea di sfruttare i punti di forza e di ottenere una mutua stabilizzazione dei due materiali, tre differenti elettrodi con differenti rapporti volumetrici BSCF:LSCF sono stati analizzati. Tutte e tre le nuove formulazioni hanno evidenziato un incremento dell’attività catalitica per la riduzione dell’ossigeno rispetto ai materiali di partenza, con valori di resistenza di polarizzazione competitivi con quelli di riferimento riportati in letteratura. Inoltre l’elettrodo con rapporto BSCF:LSCF=70:30 oltre ad avere il miglior comportamento elettrochimico, è caratterizzato da una diminuzione della velocità di degrado. Nell’ultimo anno del progetto, in collaborazione con la Technische Universitat Wien, altri due materiali sono stati accoppiati e le loro interazioni investigate. Il La0.6Sr0.4FeO3-δ (LSF), materiale molto stabile ma poco attivo, è stato combinato con il La0.6Ba0.4CoO3-δ (LBC), che fornisce un’elevatissima attività elettrocatalitica, ma soffre di instabilità. I due materiali sono stati testati in differenti sistemi a film sottile ottenuti mediante pulse laser deposition. Se mescolati prima dello step di sintering i due materiali reagiscono formando una nuova fase perovskitica attiva (Ba0.099Sr0.297La0.594Fe0.8Co0.2O3). La reazione è evitata producendo un sistema bilayer, e la presenza di un top layer di LBC sopra un film denso di LSF produce una drastica riduzione della resistenza di polarizzazione. Durante tutta la tesi particolare attenzione è stata dedicata all’integrazione di differenti approcci disponibili per analizzare i risultati sperimentali ottenuti mediante impedenza a spettroscopia elettrochimica. Hanno assunto particolare rilievo la distribuzione dei tempi di rilassamento, la simulazione con circuiti equivalenti e la modellazione basata su modelli fisici
Electrochemical oxidation of a synthetic dye using a BDD anode with a solid polymer electrolyte
No full textIn this study the performance of an electrochemical cell with a solid polymer electrolyte (SPE) has been investigated using Safranin T, a synthetic dye, as a model compound. The cell consists of a Nafion membrane sandwiched between a BDD mesh anode and a Ti/RuO2 mesh cathode operating at constant current. The effects of operating conditions such as applied current, stirring rate and electrolyte conductivity were studied. The experimental results showed that Safranin T was completely removed by reaction with [rad]OH radicals generated by water electrolysis and that the oxidation was under charge-transfer control. Furthermore, it was observed that addition of Na2SO4 to the solution decreased the removal rate but also decreased the specific energy required for the process
Electrochemical treatment of poorly biodegradable DPC cationic surfactant
No full textThe electrochemical oxidation of the cationic surfactant dodecylpyridinium chloride (DPC) was investigated using an electrolytic flow cell operating in batch recycle mode under galvanostatic conditions. The cell was equipped with a boron-doped diamond anode and a stainless steel cathode. The effects of some operating parameters, such as current density, recirculation flow-rate, and DPC concentration were investigated. DPC removal and mineralization were monitored by HPLC analyses and TOC measurements. The results show that DPC can be successfully removed and that degradation is under mass-transport control. The oxidation rate was well described by pseudo-first-order kinetics, and while the apparent rate constant increased with flow-rate, it was unaffected by DPC concentration and current density. Under optimum 5 mA cm-2 and 300 dm3 h-1 conditions, the apparent rate constant was 3.13 × 10-4 s-1. DPC solution with 75 mg dm-3 of surfactant (54 mgdm-3 of initial TOC) was completely mineralized in 330 min, achieving maximum 33% efficiency. Anodic oxidation of the cationic DPC was compared with anionic sodium dodecyl benzene sulfonate (SDBS) degradation and DPC oxidation was demonstrated to be faster and requiring less energy due to the presence of chloride ions in the DPC molecules that are oxidized to active chlorine which acts as redox mediator increasing the removal rate
Coupling a Boron Doped Diamond Anode with a Solid Polymer Electrolyte to Avoid the Addition of Supporting Electrolyte in Electrochemical Advanced Oxidation Processes
No full textThe application of electrochemical technologies to wastewater treatment is limited by solution conductivity. In this paper, a solid polymer electrolyte Nafion® membrane has been used sandwiched between a boron doped diamond (BDD) anode and Ti/RuO2 cathode meshes to treat Bismarck Brown Y (BBY) solutions with very low conductivity. BBY has been chosen as model compound to the system, and the influence of several process parameters has been investigated. During the experiments the evolution of chemical oxygen demand (COD), color removal and nitrogen compounds have been monitored. The performances were strongly related with applied current and stirring rate, changed in a range of 0.5–2 A and 200 and 850 rpm, respectively. Their increment leads to a decrease of oxidation time required to remove BBY completely. The effect of the presence of Na2SO4 (2 and 7 mM) as supporting electrolyte has been also evaluated. Results were compared with a removal treatment carried out with a conventional batch system, using a flow cell containing liquid supporting electrolyte (Na2SO4). This comparison highlighted that the new cell setup is performing better in removing organic compounds, and thus, can be considered as effective process for the treatment of solutions with a low conductivity
A high-performance Co-free electrode for solid oxide cells: La0.7Sr0.3Cu0.15Fe0.85O3-δ synthesis and characterisation
No full textA Co-free perovskite material, La0.7Sr0.3Cu0.15Fe0.85O3-δ, is synthesized and electrochemically characterized to evaluate its potential application as electrocatalyst in the air electrode of solid oxide cells. The powder was firstly synthesized by the sol-gel method and subsequently morphologically and structurally characterized by scanning electron microscope and X-ray diffraction. Symmetrical circular button cells featuring Sm-doped ceria (20% Sm) as supporting electrolyte and La0.7Sr0.3Cu0.15Fe0.85O3-δ as electrocatalyst were manufactured to carry out electrochemical investigations. Two different electrode morphologies are analyzed. In the first structure, the La0.7Sr0.3Cu0.15Fe0.85O3-δ calcined powders are directly deposited by slurry coating on a dense sintered supporting pellet of Sm-doped ceria. In the second electrode configuration, the precursor solution of La0.7Sr0.3Cu0.15Fe0.85O3-δ impregnates a porous scaffold of Sm-doped ceria, previously deposited and co-sintered with the supporting electrolyte. The performance of the samples was studied by means of electrochemical impedance spectroscopy, measuring polarization resistances of 0.0153 Ω∙cm2 at 700 °C and 0.052 Ω∙cm2 at 600 °C for the slurry coated and infiltrated electrodes, respectively. These values, according to the authors knowledge, are amongst the lowest ever obtained for Co-free solid oxides electrodes. However, the very high electrocatalytic activity obtained at intermediate temperatures is not accompanied by chemical stability over time.Fil: Cademartori, Davide. Università degli Studi di Genova; ItaliaFil: Maria Asensio, Antonio. Università degli Studi di Genova; ItaliaFil: Clematis, Davide. Università degli Studi di Genova; ItaliaFil: Basbus, Juan Felipe. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche | Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche; Argentina. Consiglio Nazionale delle Ricerche; ItaliaFil: Viviani, Massimo. Consiglio Nazionale delle Ricerche; ItaliaFil: Presto, Sabrina. Consiglio Nazionale delle Ricerche; ItaliaFil: Barbucci, Antonio. Consiglio Nazionale delle Ricerche; Italia. Università degli Studi di Genova; ItaliaFil: Carpanese, M. Paola. Consiglio Nazionale delle Ricerche; Italia. Università degli Studi di Genova; Itali
Machine Learning to Optimize Electrochemical Advanced Oxidation Processes for Low Conductive Solution – Performance and Economical Analysis
No full textApplication of boron-doped diamond electrodes for electrochemical oxidation of real wastewaters
No full textRecently, the synthesis of boron-doped diamond electrodes on different substrates and shapes have reached a promising development stage. Now, these electrodes can also be effectively used to destroy toxic or biorefractory organics in real effluents, such as municipal wastewaters effluents, hospital wastewaters, groundwater, petrochemical effluent, wastewaters from agri-food activities, and so on. The results of this mini-review show that BDD is effectively even for such real effluents, allowing the removal of pollutants under several different conditions. Nevertheless, further efforts are necessary to reach a wider market; in particular, the next stages must face the optimization of cell design and the integration of the electrochemical system with other water treatment and renewable energy sources
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