Carbon modified (CM)-n-TiO2 thin films for efficient water splitting to H2 and O2 under xenon lamp light and natural sunlight illuminations

Visible light-active carbon modified n-type titanium oxide (CM-n-TiO₂) thin films were synthesized by both flame oxidation and a combination of spray pyrolysis and flame oxidation. An undoped reference sample was also synthesized in an electric oven for comparison. Photoresponse of CM-n-TiO₂ and n-TiO₂ was evaluated by measuring the rates of water splitting to hydrogen and oxygen, in terms of observed photocurrent densities. Under monochromatic illumination from a xenon lamp, the integrated photocurrent densities from 300 nm to wavelengths corresponding to band gaps were found to be 1.12, 7.7, and 12.7 mA cm⁻² for optimized oven-made n-TiO₂ (sample 1), flame-made (sample 2), and spray pyrolysis flame-made CM-n-TiO₂ (sample 3) thin films at 0.48, 0.24, and 0.215 V biases, respectively. The corresponding maximum photoconversion efficiencies for these thin films were 0.84%, 7.62%, and 12.89%, respectively. Under actual natural global AM 1.5 sunlight illumination of 1 sun, the photocurrent densities for water splitting were 0.85, 5.89, and 12.27 mA cm⁻² for samples 1, 2, and 3, respectively. These photocurrent densities generated the maximum photoconversion efficiencies of 0.67%, 5.63%, and 12.26% for samples 1, 2, and 3, respectively, under global sunlight illuminations. These values compared well with those found under monochromatic light illumination from the xenon lamp. The increasing efficiencies were found to be consistent with lowering of main band gap from 3.0 eV to 2.65 eV and the generation of mid-gap bands at 1.6 eV and 1.4 eV above the valence band for samples 2 and 3, respectively. Carbon contents were found to be 0.0, 17.60, and 23.23 atom% for samples 1, 2, and 3, respectively. Dedicated to the 85th birthday of John O’ M. Bockris.     

The capacity of thin passive films

The capacity of thin passive films on metal electrodes is investigated. Two contributions are reported: one from the space charge in the film and one from the surface charge on the underlying metal. In the usual Schottky-Mott plot such films also exhibit a linear region, but this cannot ordinarily be used to obtain the carrier concentration and the flat-band potential. These calculations agree well with experimental data.     

Potassium ferro-cyanide trihydrate complex catalyzed one-pot synthesis of 2-phenylimidazo[4,5-f][1,10] phenanthroline

Various 2-phenylimidazo[4,5-f][1,10]phenanthrolines were synthesized from potassium ferro-cyanide trihydrate(KFCT) complex catalyzed three component reaction of 1,10-phenanthroiine-5,6-dione,aromatic aldehydes and ammonium acetate at room temperature in excellent isolated yield.This is a simple and straight forward,high yielding,not involving any hazardous or expensive catalyst method.     

Simultaneous separation and extraction of Ag(I), Pb(II) and Pd(II) ions by solid phase method and determination of these ions by flame atomic absorption spectrometry

A simultaneous preconcentration and separation method for determination of trace amount of dissolved Ag⁺, Pb²⁺ and Pd²⁺ ions by modified octadecyl silica membrane disks with DBzDA18C6 was developed. The adsorbed metal complexes were eluted from disk with 10?mL of 4?M KCl and determined by flame atomic absorption spectroscopy. Several parameters such as anion effect, pH of sample solution, type of eluent, amount of ligand, sample and elution flow rate were evaluated. The effect of diverse ions on preconcentration was also investigated. A precocentration factor of 110 can easily be achieved depending on the volume of the sample. For 100?mL of the solution the linear dynamic rang were found to be 30–1000, 140–6000, 60–900?μg?l^?1 for Ag⁺, Pb²⁺ and Pd²⁺, respectively. Based on three standard deviation of the blank the detection limit was obtained as 1.8, 8.0 and 4.2?μg?L^?1 for Ag⁺, Pb²⁺, Pd²⁺, respectively. The formation constants of Ag⁺ and Pb²⁺ ions with DBzDA18C6 at 25?°C were determined from the molar conductance–mole ratio data. This method was applied for the determination of Ag⁺, Pb²⁺ and Pd²⁺ in environmental water, tea and soil samples.