Photoelectrochemical behavior of electrophoretically deposited hematite thin films modified with ti(IV)

: Doping hematite with different elements is a common strategy to improve the electrocatalytic activity towards the water oxidation reaction, although the exact effect of these external agents is not yet clearly understood. Using a feasible electrophoretic procedure, we prepared modified hematite films by introducing in the deposition solution Ti(IV) butoxide. Photoelectrochemical performances of all the modified electrodes were superior to the unmodified one, with a 4-fold increase in the photocurrent at 0.65 V vs. SCE in 0.1 M NaOH (pH 13.3) for the 5% Ti-modified electrode, which was the best performing electrode. Subsequent functionalization with an iron-based catalyst led, at the same potential, to a photocurrent of ca. 1.5 mA?cm-2 , one of the highest achieved with materials based on solution processing in the absence of precious elements. AFM, XPS, TEM and XANES analyses revealed the formation of different Ti(IV) oxide phases on the hematite surface, that can reduce surface state recombination and enhance hole injection through local surface field effects, as confirmed by electrochemical impedance analysis

New Components for Dye-Sensitized Solar Cells

Dye-Sensitized Solar Cells (DSSCs) are among the most promising solar energy conversion devices of new generation, since coupling ease of fabrication and low cost offer the possibility of building integration in photovoltaic windows and facades. Although in their earliest configuration these systems are close to commercialization, fundamental studies are still required for developing new molecules and materials with more desirable properties as well as improving our understanding of the fundamental processes at the basis of the functioning of photoactive heterogeneous interfaces. In this contribution, some recent advances, made in the effort of improving DSSC devices by finding alternative materials and configurations, are reviewed

correction on the stability of manganese tris β diketonate complexes as redox mediators in dsscs

Correction for 'On the stability of manganese tris(β-diketonate) complexes as redox mediators in DSSCs' by Stefano Carli et al., Phys. Chem. Chem. Phys., 2016, 18, 5949–5956

Studio di complessi mononucleari e di sistemi supramolecolari inorganici per la sensibilizzazione spettrale del biossido di titanio: sviluppo di celle fotoelettrochimiche rigenerative per la conversione dell'energia solare

Dottorato di ricerca in scienze chimiche. 6. ciclo. A.a. 1990-94. Relatori C. A. Bignozzi e F. ScandolaConsiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7, Rome; Biblioteca Nazionale Centrale - P.za Cavalleggeri, 1, Florence / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

Sedimentation field flow fractionation and optical absorption spectroscopy for a quantitative size characterization of silver nanoparticles

Many advanced industrial and biomedical applications that use silver nanoparticles (AgNPs), require that particles are not only nano-sized, but also well dispersed, not aggregated and not agglomerated. This study presents two methods able to give rapidly sizes of monodispersed AgNPs suspensions in the dimensional range of 20-100nm. The first method, based on the application of Mie's theory, determines the particle sizes from the values of the surface plasmon resonance wavelength (SPRMAX), read from the optical absorption spectra, recorded between 190nm and 800nm. The computed sizes were compared with those determined by transmission electron microscopy (TEM) and dynamic light scattering (DLS) and resulted in agreement with the nominal values in a range between 13% (for 20nm NPs) and 1% (for 100nm NPs), The second method is based on the masterly combination of the Sedimentation Field Flow Fractionation (SdFFF - now sold as Centrifugal FFF-CFFF) and the Optical Absorption Spectroscopy (OAS) techniques to accomplish sizes and quantitative particle size distributions for monodispersed, non-aggregated AgNPs suspensions. The SdFFF separation abilities, well exploited to size NPs, greatly benefits from the application of Mie's theory to the UV-vis signal elaboration, producing quantitative mass-based particle size distributions, from which trusted number-sized particle size distributions can be derived. The silver mass distributions were verified and supported by detecting off-line the Ag concentration with the graphite furnace atomic absorption spectrometry (GF-AAS)

Electrochromic devices based on wide band-gap nanocrystalline semiconductors functionalized with mononuclear charge transfer compounds

A series of ruthenium and iron mononuclear complexes were prepared and their spectroeletrochemical behavior characterized oil Optically Transparent Thin Layer Electrodes (OTTLE) and on Fluorine Doped SnO2 (FTO) conductive glasses coated with Sb-doped nanocrystalline SnO2. These systems display a reversible electrochemical response and offer potential application in electrochromic devices. On SnO2 films distinct spectral changes are observed in a narrow potential range (-0.5/0.9 V vs SCE) with switching times of the order of 0.8 s

METHOD OF PREPARATION OF MONONUCLEAR RUTHENIUM COMPLEXES

The invention refers to a process for the preparation of inorganic dyes, useful as spectral sensitizers for semiconductors, wherein the intermediate [Ru(dcb)2(C2O4)]4- is used

Solvatochromic Dye Sensitized Nanocrystalline Solar Cells

The coordination compound TBA(4)[Ru(CN)(4)(dcb)], where TBA is tetrabutylammonium and dcb is 4,4'-(CO2-)(2)-2,2'-bipyridine, was synthesized and attached to optically transparent nanocrystalline (anatase) TiO2 films, abbreviated [Ru(CN)(4)(dcb)]/TiO2. The metal-to-ligand-charge-transfer (MLCT) absorption and emission bands were found to shift in wavelength with solvent. The absorption maximum of the low energy MLCT band was observed at 517 nm in acetonitrile and 535 nm in dimethylformamide for TBA(4)[Ru(CN)(4)(dcb)] and at 470 and 500 for [Ru(CN)(4)(dcb)]/TiO2, respectively. Pulsed light excitation of TBA(4)[Ru(CN)(4)(dcb)] in acetonitrile produces a long-lived emissive MLCT excited state, tau = 30 ns. Pulsed light excitation of [Ru(CN)(4)(dcb)]/TiO2 yields an absorption difference spectrum attributed to an interfacial charge separated state, [Ru-III(CN)(4)(dcb)]/TiO2(e(-)). This state forms within 10 ns and returns cleanly to ground-state product within milliseconds. Regenerative solar cells based on [Ru(CN)(4)(dcb)]/TiO2 were prepared whose spectral sensitivity and efficiency were a function of the solvent used with 0.5 M Lil and 0.05 M I-2. The maximum incident photon-to-current efficiency (IPCE) was measured at 480 nm (25%) in acetonitrile and 510 nm (5%) in dimethylformamide. This work reports a new approach for controlling the spectral sensitivity of solar cells and for probing the solvation of molecules anchored to nanocrystalline semiconductor surfaces

Charge Transfer Dynamics at Modified Hematite Photoanodes

The photoelectrochemical behavior of colloidal hematite photoelectrodes, prepared by either hydrothermal or electrophoretic means and modified with Fe(III) based water oxidation catalysts and a compact blocking underlayer is discussed with regard to the electron/hole charge transfer and recombination kinetics. While the presence of an amorphous iron oxide catalyst allows for the trapping of photoholes in reactive states at interface with the electrolyte, the presence of a compact hematitic underlayer between the porous semiconductor and the FTO electron collector improves the selectivity of the back contact to electrons, thus reducing recombination due to accumulation of charge carriers within the film under illumination. A considerable improvement of the photoelectrochemical efficiency follows