Photocatalytic reaction over iron hydroxides: A novel visible-light-responsive photocatalyst

Photocatalytic properties of iron hydroxide (FeOOH) particles prepared by a hydrothermal method were estimated under visible-light irradiation. Hydrothermal treatment in the presence of ethanol induced α-FeOOH (goethite) formation even under an acidic condition, while the presence of chloride ion led to preferential formation of β-FeOOH (akaganeite). α-FeOOH particles with largest specific surface area showed the highest photocatalytic activity among commercial and prepared FeOOH samples and exhibited total decomposition of acetaldehyde even under visible-light irradiation. The progress of photocatalytic reaction may be due to multi-electron reduction of oxygen over FeOOH particles

Solution-processed amorphous niobium oxide as a novel electron collection layer for inverted polymer solar cells

Amorphous niobium oxide (NbOx) as an electron collection layer in inverted polymer solar cells was prepared by a solution process. The power conversion efficiency of inverted polymer solar cells based on a blend of poly(3-hexylthiophene) and [6,6]-phenyl C61 butyric acid methyl ester was improved to 2.22% by inserting an NbOx layer between the active layer and indium tin oxide electrode. An energy level diagram of component materials in the inverted polymer solar cell indicated that the NbOx layer works as both an electron collection layer and hole blocking layer in polymer solar cells

Photoelectrochemical CO2 reduction by a p-type boron-doped g-C3N4 electrode under visible light

Graphitic carbon nitride (g-C3N4) has attracted much attention as a metal-free semiconductor having visible light absorption and relatively high chemical stability under visible light irradiation. Graphitic carbon nitride (g-C3N4) and boron-doped g-C3N4 (B-doped g-C3N4, BCNx) were prepared by heating melamine and a mixture of dicyanodiamide and BH3NH3, respectively. X-ray diffraction, a Brunauer, Emmett and Teller (BET) apparatus, and UV–vis spectra were used to analyze the physical properties of the prepared samples. Electrodes of these samples were prepared by using the electrophoresis method. X-ray photoelectron spectroscopy analyses confirmed the incorporation of boron atoms in the g-C3N4 framework as well as the amount of boron atoms.Au, Ag or Rh as a co-catalyst was coated on the surface of g-C3N4 and B-doped g-C3N4 by using the magnetron sputtering method. The photocurrent response was observed using a solar simulator as a light source. The photocurrent response of B-doped g-C3N4 was about 5-times larger than that of pure g-C3N4. B-doped g-C3N4 coated with Rh as a co-catalyst showed the highest photocurrent response under solar light irradiation, its photocurrent being about 10-times larger than that of original g-C3N4. Under photoelectrochemical conditions, we also observed the products in gas phase and aqueous phase. C2H5OH was observed as a main product, while small amounts of CO and H2 were observed in gas phase. We also discuss the relationship between co-catalysts and photocurrent responses and the carbon source of C2H5OH as a main product. The source of carbon of C2H5OH obtained by CO2 reduction is discussed on the basis of results of a labeling experiment using 13CO2

Photocatalytic partial oxidation of methylpyridine isomers on TiO2 particles under an anaerobic condition

Photocatalytic oxidation of methylpyridine isomers (2-methylpyridine, 3-methylpyridine, and 4-methylpyridine) was investigated in a mixed solution of acetonitrile and water or acetonitrile using various kinds of TiO2 powders as photocatalysts. The main products from methylpyridine isomers were pyridinecarboxaldehyde isomers (2-pyridinecarboxaldehyde, 3-pyridinecarboxaldehyde, and 4-pyridinecarboxaldehyde). Rutile large TiO2 particles showed the highest level of activity for oxidation of 2-methylpyridine probably because band bending was necessary for the oxidation of 2-methylpyridine. On the other hand, a fine particle having an anatase or rutile phase showed a higher level of activity than large TiO2 particles for oxidation of 3-methylpyridine. A rutile fine particle showed the highest level of activity for the reaction. It was found that pure rutile or pure anatase particles were inactive for oxidation of 4-mathylpyridine. If the particles are not extremely small, pure rutile and pure anatase powders show fairly high levels of activity, and those containing both anatase and rutile phases show the highest level of activity. The activity of pure rutile particles was also enhanced by physically mixing them with a small amount of small anatase particles, which were inactive for this reaction. These results can be explained by the synergism between rutile and anatase particles. All of these reactions effectively proceeded even under anaerobic conditions. Photocatalytic reduction of methylpyridine isomers concomitantly proceeded on TiO2 particles under the conditions used. These results suggest that the activities of TiO2 photocatalysts for oxidation of methylpyridine isomers are dominated by the oxidation potential of alkylpiridine and band bending of TiO2 particles

Oxidation of Aldehydes on TiO2 Photocatalysts Modified with Alkylsilyl Group

Surfaces of SiO2-covered TiO2 photocatalysts were modified with alkylsilyl groups. Oxidation of hexanal on surface-modified TiO2 proceeded more efficiently than that on photocatalysts without surface modification. The improvement of the photocatalytic activities of surface-modified TiO2 photocatalysts is due to the hydrophobic interaction between hexanal and alkylsilyl groups modified on TiO2 photocatalysts

Selective Oxidation of Benzaldehyde Derivatives on TiO2 Photocatalysts Modified with Fluorocarbon Group

Fluorocarbon groups were introduced onto surfaces of SiO2-covered TiO2 particles (SiO2–TiO2). Oxidation of pentafuluorobenzaldehyde on the surface modified TiO2 powders proceeded much efficiently than that on SiO2-covered TiO2 particles without surface modification. In addition, no enhancement of activity level of surface-modified SiO2–TiO2 for oxidation of benzaldehyde was observed. The enhancement of the surface-modified SiO2–TiO2 is due to the interaction of F atoms between the substrate and fluorocarbon groups introduced on SiO2–TiO2