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11.
Nanostructured α‐Fe2O3 thin film electrodes were deposited by aerosol‐assisted chemical vapour deposition (AACVD) for photoelectrochemical (PEC) water splitting on conducting glass substrates using 0.1 M methanolic solution of Fe(acac)3. The XRD analysis confirmed that the films are highly crystalline α‐Fe2O3 and free from other iron oxide phases. The highly reproducible electrodes have an optical bandgap of ~2.15 eV and exhibit anodic photocurrent. The current–voltage characterization of the electrodes reveals that the photocurrent density strongly depended on the film morphology and deposition temperature. Scanning electron microscopy (SEM) analysis showed a change in the surface morphology with the change in deposition temperature. The films deposited at 450 °C have nanoporous structures which provide a maximum electrode/electrolyte interface. The maximum photocurrent density of 455 µA/cm2 was achieved at 0.25 V vs. Ag/AgCl/3M KCl (~1.23 V vs. RHE) and the incident photon to electron conversion efficiency (IPCE) was 23.6% at 350 nm for the electrode deposited at 450 °C. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
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We examine the discrete free boundaries arising from a finiteelement discretization of a variational inequality. We giveL error bounds for the Hausdorff distance of the discrete andtrue free boundary, as well as for the normals. The theoreticalresults are confirmed by numerical experiments in two and threedimensions. 相似文献
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The efficiency of dye-sensitised nanocrystalline solar cells is limited in part by the back reaction of photo-injected electrons with tri-iodide ions present in the electrolyte. Competition between this back reaction and the collection of electrons by diffusion to the substrate contact can be described in terms of the electron diffusion length Ln=(Dnτn)1/2, where Dn is the electron diffusion coefficient and τn is the electron lifetime determined by the rate of reaction of electrons with tri-iodide. Dn and τn have been determined over five orders of magnitude of illumination intensity using intensity-modulated photocurrent and intensity-modulated photovoltage spectroscopy. It has been found that τn decreases with light intensity, whereas Dn increases. As a consequence, the electron diffusion coefficient Ln is only weakly intensity dependent, and the incident photon to current conversion efficiency (IPCE) is predicted to be almost independent of intensity. The experimental IPCE agrees well with the predicted values. The results suggest that the kinetics of the back reaction of electrons with tri-iodide couple may be second order in electron density. 相似文献
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Upul Wijayantha KG Saremi-Yarahmadi S Peter LM 《Physical chemistry chemical physics : PCCP》2011,13(12):5264-5270
Photoelectrochemical Impedance Spectroscopy (PEIS) has been used to characterize the kinetics of electron transfer and recombination taking place during oxygen evolution at illuminated polycrystalline α-Fe(2)O(3) electrodes prepared by aerosol-assisted chemical vapour deposition from a ferrocene precursor. The PEIS results were analysed using a phenomenological approach since the mechanism of the oxygen evolution reaction is not known a priori. The results indicate that the photocurrent onset potential is strongly affected by Fermi level pinning since the rate constant for surface recombination is almost constant in this potential region. The phenomenological rate constant for electron transfer was found to increase with potential, suggesting that the potential drop in the Helmholtz layer influences the activation energy for the oxygen evolution process. The PEIS analysis also shows that the limiting factor determining the performance of the α-Fe(2)O(3) photoanode is electron-hole recombination in the bulk of the oxide. 相似文献
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Sultan M Tahir AA Mazhar M Wijayantha KG Zeller M 《Dalton transactions (Cambridge, England : 2003)》2011,40(31):7889-7897
The mixed metal complex [Zn(TFA)(3)(μ-OH)Cu(3)(dmae)(3)Br]·THF (1) and its isostructural analogues ([Zn(TFA)(3)(μ-OH)Cu(3)(dmae)(3)Cl]·THF (2) and [Zn(TFA)(3)(μ-OH)Cu(3)(dmae)(3)Cl/Br]·THF (3)) have been prepared by a simple metal ligand assembly method and were characterized by their melting points, elemental analysis, IR spectroscopy, thermogravimetry and single crystal X-ray structures. The compounds are distinguished only by the nature of the halide ions and are made up of the same [Zn(TFA)(3)(μ-OH)Cu(3)(dmae)(3)X]·THF molecular building block with Cu(3)ZnO(4) cubane moieties as the central core in which the four metal ions and four oxygen atoms are joined together in alternate positions of the cuboid. All the complexes crystallize with similar packing and crystallographically related symmetry settings, distinguished mainly by the degree of disorder within the complexes and the ordering of the complexes in the structures. The triclinic cell of (1) emulates the monoclinic cell of (2) and is pseudomerohedrally twinned by a symmetry operation of the monoclinic cell. The molecules in (2) are 1:1 disordered around a crystallographic mirror plane. The structure of the mixed halogen compound (3) in turn is a superstructure of the less symmetric structures of (1) and (2) formed by ordering of the complexes along the longest axis of (3). Aerosol-assisted chemical vapour deposition (AACVD) experiments showed that they are promising precursors to deposit thin films of crystalline Cu/ZnO composites. The surface morphology, microstructure, chemical composition and crystallinity of the resulting Cu/ZnO composite thin films were analysed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDAX), which suggest that the films are thin, crystalline, uniform, smooth and tightly adherent to the substrates with average crystallite sizes in a range between 40.2 and 80.0 nm. Particle sizes, shapes and film morphology were investigated as a function of precursor and decomposition temperature. 相似文献
17.
Cummings CY Marken F Peter LM Tahir AA Wijayantha KG 《Chemical communications (Cambridge, England)》2012,48(14):2027-2029
Rate constants for recombination and hole transfer during oxygen evolution at illuminated α-Fe(2)O(3) electrodes were measured by intensity-modulated photocurrent spectroscopy and found to be remarkably low. Treatment of the electrode with a Co(II) solution suppressed surface recombination but did not catalyse hole transfer. Intermediates in the reaction were detected spectroscopically. 相似文献