Photoelectrochemical generation of hydrogen using 100 Mev Si8+ ion irradiated electrodeposited iron oxide thin films (original) (raw)
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Japanese Journal of Applied Physics, 2011
Surface modifications using platinum (Pt) particles and iron oxides (FeO x) were found to lead to a significant improvement in the current-potential (J-E) properties for hydrogen evolution from water in p-type silicon (p-Si) electrodes. The onset potential and cathodic photocurrent for hydrogen evolution from the Pt/p-Si(100) electrode were, respectively, 0.50 V RHE and 0.28 mA/cm 2 at 0 V RHE (RHE: reversible hydrogen electrode). When the p-Si(100) electrode was coated with iron oxide followed by Pt particles [Pt/FeO x /p-Si(100)], it showed an onset potential and photocurrent of 0.85 V RHE and 2.45 mA/cm 2 at 0 V RHE , respectively. A detailed study of surface morphology and a comparative study between (100) plane and (111) plane p-Si electrodes revealed that the dramatic improvement in J-E properties was the result of a change in the surface structure and tailing of FeO x in p-Si.
Solid-state photoelectrochemical H2 generation with gaseous reactants
Electrochimica Acta, 2013
Photocurrent and H 2 production were demonstrated in an all solid-state photoelectrochemical cell employing gaseous methanol and water vapour at the photoanode. Open circuit photovoltage of around −0.4 V and short circuit photocurrent of up to 250 A/cm 2 were obtained. At positive bias, photocurrent generation was limited by the irradiance, i.e., the amount of photogenerated charge carriers at the anode. Time constants and impedance spectra showed an electrochemical capacitance of the cell of about 15 F/cm 2 in the dark, which increased with increasing irradiance. With only water vapour at the anode, the short circuit photocurrent was about 6% of the value with gaseous methanol and water vapour. The photoanode and electrocatalyst on carbon paper support were affixed to the proton conducting membrane using Nafion ® as adhesive, an approach that yielded photocurrents up to 15 times better than that of a cell assembled by hot-pressing, in spite of the overall cell resistance of the latter being up to five times less than that of the former. This is attributed, at least partially, to reactants being more readily available at the photoanode of the better performing cell.
Iron doped nanostructured TiO 2 for photoelectrochemical generation of hydrogen
International Journal of Hydrogen Energy, 2008
Iron doping TiO 2 Sol-gel a b s t r a c t This paper describes the photoelectrochemical studies on nanostructured iron doped titanium dioxide (TiO 2 ) thin films prepared by sol-gel spin coating method. Thin films were characterized by X-ray diffraction, Raman spectroscopy, spectral absorbance, atomic force microscopy and photoelectrochemical (PEC) measurements. XRD study shows that the films were polycrystalline with the photoactive anatase phase of TiO 2 . Doping of Fe in TiO 2 resulted in a shift of absorption edge towards the visible region of solar spectrum. The observed bandgap energy decreased from 3.3 to 2.89 eV on increasing the doping concentration upto 0.2 at.% Fe. 0.2 at.% Fe doped TiO 2 exhibited the highest photocurrent density, w0.92 mA/cm 2 at zero external bias. Flatband potential and donor density determined from the Mott-Schottky plots were found to vary with doping concentration from À0.54 to À0.
Hydrogen is considered to be an ideal energy carrier, which produces only water when combined with oxygen and thus has no detrimental effect on the environment. While the catalytic decomposition of hydrous hydrazine for the production of hydrogen is well explored, little is known about its photocatalytic decomposition. The present paper describes a highly efficient photochemical methodology for the production of hydrogen through the decomposition of aqueous hydrazine using titanium dioxide nanoparticles modified with a Rh(I) coordinated catechol phosphane ligand (TiO 2 –Rh) as a photocatalyst under visible light irradiation. After 12 h of visible light irradiation, the hydrogen yield was 413 μmol g −1 cat with a hydrogen evolution rate of 34.4 μmol g −1 cat h −1. Unmodified TiO 2 nanoparticles offered a hydrogen yield of 83 μmol g −1 cat and a hydrogen evolution rate of only 6.9 μmol g −1 cat h −1. The developed photocatalyst was robust under the experimental conditions and could be efficiently reused for five subsequent runs without any significant change in its activity. The higher stability of the photocatalyst is attributed to the covalent attachment of the Rh complex, whereas the higher activity is believed to be due to the synergistic mechanism that resulted in better electron transfer from the Rh complex to the conduction band of TiO 2 .
Photoelectrochemical hydrogen production using nanostructured α-Fe2O3 electrodes
Proceedings of SPIE - The International Society for Optical Engineering, 2006
This work involves development of coaxial tubular annular photoelectrochemical reactor for hydrogen production from treatment of industrial sulfide effluent. The use of SnS as photocatalyst in a slurry reactor has been investigated. Effects of concentrations of sodium sulfide and sulfite and photocatalyst(SnS) loading on hydrogen production have been studied. For each reaction slurry there is optimum amount of catalyst loading. For instance , volume of hydrogen produced will be maximum at the catalyst loading of 0.33 g/l in reaction slurry of 0.25M sodium sulfide concentration and 0.25M sodium sulfite concentration. Further increase in the catalyst loading decreases the volume of hydrogen produced due to screening effect.
Photo-catalytic hydrogen production over Fe2O3 based catalysts
International Journal of Hydrogen Energy, 2010
The hydrogen photo-evolution was successfully achieved in aqueous (Fe 1Àx Cr x) 2 O 3 suspensions (0 x 1). The solid solution has been prepared by incipient wetness impregnation and characterized by X-ray diffraction, BET, transport properties and photo-electrochemistry. The oxides crystallize in the corundum structure, they exhibit ntype conductivity with activation energy of w0.1 eV and the conduction occurs via adiabatic polaron hops. The characterization of the band edges has been studied by the Mott Schottky plots. The onset potential of the photo-current is w0.2 V cathodic with respect to the flat band potential, implying a small existence of surface states within the gap region. The absorption of visible light promotes electrons into (Fe 1Àx Cr x) 2 O 3-CB with a potential (wÀ0.5 V SCE) sufficient to reduce water into hydrogen. As expected, the quantum yield increases with decreasing the electro affinity through the substitution of iron by the more electropositive chromium which increases the band bending at the interface and favours the charge separation. The generated photo-voltage was sufficient to promote simultaneously H 2 O reduction and SO 3 2À oxidation in the energetically downhill reaction (H 2 O þ SO 3 2À / H 2 þ SO 4 2À , DG ¼ À17.68 kJ mol À1). The best activity occurs over Fe 1.2 Cr 0.8 O 3 in SO 3 2À (0.1 M) solution with H 2 liberation rate of 21.7 mmol g À1 min À1 and a quantum yield 0.06% under polychromatic light. Over time, a pronounced deceleration occurs, due to the competitive reduction of the end product S 2 O 6 2À .
We report the development of a cobalt phosphide nanoarray as an efficient and stable catalyst for the hydrazine oxidation reaction (HzOR) in alkaline media. Its high hydrogen evolution reaction (HER) activity enables it to be used as a bifunctional catalyst for less energy-intensive electrolytic hydrogen generation by replacing the sluggish oxygen evolution reaction with HzOR. The corresponding two-electrode electrolyzer using such a nanoarray as both the anode for HzOR and the cathode for HER only needs a cell voltage of 0.2 V to drive 10 mA cm À2 in 1.0 M KOH with 100 mM hydrazine, which is 1.45 V less than that for pure water splitting. This electrolyzer also shows strong long-term electrochemical durability with nearly 100 % faradic efficiency for hydrogen evolution.