1,720,976 research outputs found
Impact of air oxygen presence on the stability of the V3+ ions in the vanadium redox flow batteries
Full text linkQuesto lavoro intende definire il ruolo dell'ossigeno sulla stabilità dello ione vanadio V(III) nelle batterie di flusso redox vanadio. La spettrofotometria UV-visibile ha evidenziato che, non solo la presenza di ossigeno nella soluzione anodica limita fortemente la riduzione da V(IV) a V(II) a causa della rapida ossidazione del V(II) da parte dell’ossigeno disciolto. Più importante, la presenza di ossigeno nella stessa soluzione rende anche gli ioni V(III) molto instabili e soggetti ad ossidazione in tempi brevi. Questo effetto, mai precedentemente ben quantificato, mostra che la presenza di O2 deve essere assolutamente esclusa nel serbatoio di accumulo per mantenere stabile la concentrazione di V(III).This work is intended to define the role of oxygen on the stability of vanadium ions V(III) in the vanadium redox flow batteries. The UV-visible spectrophotometry revealed that, not only the oxygen presence in the anolyte solution strongly limits the V(IV) to V(II) reduction in the negative half-cell electrolyte, due to the rapid oxidation of the V(II) by dissolved oxygen. Most important, the oxygen presence in the same solution also makes very unstable the V(III) ions that tend to be oxidized in short time. This effect, never previously well quantified, shows that the presence of O2 must be absolutely excluded in the storage reservoir in order to keep stable the concentration of V(III)
Effect of Low Cobalt Loading on TiO2 Nanotube Arrays for Water-Splitting
Full text linkThis work is intended to define a new possible methodology for the TiO2 doping through the use of an electrochemical deposition of cobalt directly on the titanium nanotubes obtained by a previous galvanostatic anodization treatment in an ethylene glycol solution. This method does not seem to cause any influence on the nanotube structure, showing final products with news and interesting features with respect to the unmodified sample. Together with an unmodified photoconversion efficiency under UV light, the cobalt doped specimen reports an increase of the electrocatalytic efficiency for the oxygen evolution reaction (OER)
Effect of Tantalum doping on TiO2 nanotube arrays for water-splitting
Full text linkThis work is intended to define a new possible methodology for TiO2 doping through the use of electrochemical deposition of tantalum directly on the titanium nanotubes obtained by a previous galvanostatic anodization treatment in an ethylene glycol solution. This method does not seem to cause any influence on the nanotube structure, showing final products with news and interesting features with respect to the unmodified sample. Together with a decrease in the band gap and flat band potential of the TiO2 nanotubes, the tantalum doped specimen reports an increase of the photo conversion efficiency under UV light
Palladium-based hollow cathode electrolysers for hydrogen production.
No full textAbstract : Ultra-pure hydrogen can be obtained through the use of water electrolysers with dense metal cathodes. In this chapter, the theory of hydrogen evolution over Pd-based cathodes and its permeation through dense metal walls is introduced, and the Damköhler − Peclet analysis for these membrane reactors is described. Optimization of the electrolysis
process is considered, based on the relationship of DaPe number with the cell overpotential and the apparent activation energy of permeation. Literature studies on hollow cathode water electrolysers are discussed, as are new prototypes using thin-wall Pd–Ag permeator tubes, and the efficient operation of cell effi ciency and surface activation/deactivation
phenomena. The main applications of cells with Pd-based hollow cathodes are the production of ultra-pure hydrogen at high pressure for small scale laboratory electrolysers and the treatment of tritiated water. The results of tests on prototypes are examined in detail, and attention is given to future trends in material development
Nickel-TiO2 nanotube anode for photo-electrolysers
No full textThis work evaluated a new combined electrode constituted by porous nickel and an array of highly ordered TiO2 nanotubes achieved by a former galvanostatic anodization treatment in an ethylene glycol solution. The photo-electrochemical response of the composite anode was appraised. It showed a mixed behaviour with interesting features with respect to its single components. Based on the characterization of the single electrode, a composite multi-anode has been realized and tested with direct sunlight exposition in a small photo-electrolyser. The system showed good solar conversion efficiency together with a reduction in energy consumption. The results highlighted that a photo-electrolyser, operating with a cell voltage of 2 V and with a correct insulation, guaranteed by an appropriate design and an optimal management of the gas products, could reduce by at least 3.5% its energy demand. Such a combination of materials makes the new system able to work both in dark and under solar light exposure, thus opening new perspectives for industrial-scale applications
Produzione di metano da carbone con l'uso di fonti energetiche rinnovabili
No full textPer coniugare un più ampio sfruttamento del carbone e delle fonti energetiche rinnovabili, è stato studiato un processo che prevede
la produzione di idrogeno da eolico o solare e, quindi, la conversione di carbone in metano attraverso reazioni di idro-gassificazione.
Un’analisi economica preliminare mostra che questo processo potrebbe essere vantaggiosamente applicato all’area del Sulcis
in Sardegna.A process aimed at the exploitation of both coal reserves and renewable energies has been studied. It produces hydrogen from wind or solar and, then,
methane via coal hydro-gasification. A preliminary economic analysis demonstrated the applicability of such a process to the Sulcis coalfield in Sardinia
Realizzazione e prova di celle complete da laboratorio. Test elettrochimici di miscele elettrolitiche miste in semicelle e celle complete
No full textIl presente rapporto descrive la caratterizzazione di miscele elettrolitiche miste, sviluppate nell’ambito dell’Accordo di Programma ENEA-MSE per celle litio-ione destinate ad applicazioni alle reti elettriche, in semicelle catodiche e anodiche. Queste ultime sono state realizzate utilizzando gli elettrodi costituiti dai materiali attivi LiFePO4 e TiO2, selezionati nel corso delle attività svolt
Assessment of the electrostatic field uniformity within an electrospinning device
No full textThe analysis carried out made it possible to evaluate the electrostatic field in an electrospinning device by means of a Comsol finite element model. The study focuses on the main factors affecting the generation of nanofibers and on the uniformity of the electrostatic field over the collector. In particular, the behaviour of the electrostatic field vector close to the needle and along the edges of the collector was assessed. Finally, the electric field at several points on the collector surface was computed in Comsol. The obtained data were processed in Matlab to assess the variation of the electric field along the x; -and y -directions. The model results allow to explain interesting aspects arising from the use of the machine
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