Showing papers by "Kazuhiko Maeda published in 2005"
TL;DR: This is the first example of achieving overall water splitting by a photocatalyst with a band gap in the visible light region, which opens the possibility of new non-oxide-type photocatalysts for energy conversion.
Abstract: Photocatalytic overall water splitting has been studied extensively from the viewpoint of solar energy conversion Despite numerous attempts, none have yielded satisfactory results for the development of photocatalysts, which work under visible light irradiation to efficiently utilize solar energy We report here the first example of visible-light-driven overall water splitting on a novel oxynitride photocatalyst, a solid solution of GaN and ZnO with a band gap of 258-276 eV, modified with RuO2 nanoparticles In contrast to the conventional non-oxide photocatalysts, such as CdS, the solid solution is stable during the overall water splitting reaction This is the first example of achieving overall water splitting by a photocatalyst with a band gap in the visible light region, which opens the possibility of new non-oxide-type photocatalysts for energy conversion
1,280 citations
TL;DR: The crystallinity of the catalyst is also found to increase with increasing the ratio of ZnO to Ga(2)O(3) in the starting material, resulting in an increase in activity.
Abstract: The physical and photocatalytic properties of a novel solid solution between GaN and ZnO, (Ga1-xZnx)(N1-xOx), are investigated. Nitridation of a mixture of Ga2O3 and ZnO at 1123 K for 5−30 h under NH3 flow results in the formation of a (Ga1-xZnx)(N1-xOx) solid solution with x = 0.05−0.22. With increasing nitridation time, the zinc and oxygen concentrations decrease due to reduction of ZnO and volatilization of zinc, and the crystallinity and band gap energy of the product increase. The highest activity for overall water splitting is obtained for (Ga1-xZnx)(N1-xOx) with x = 0.12 after nitridation for 15 h. The crystallinity of the catalyst is also found to increase with increasing the ratio of ZnO to Ga2O3 in the starting material, resulting in an increase in activity.
380 citations
TL;DR: The enhancement of catalytic activity by Ru loading from Ru(3)(CO)(12) is shown to be dependent on the formation of crystalline RuO(2) nanoparticles with optimal size and coverage.
Abstract: The formation and structural characteristics of Ru species applied as a cocatalyst on (Ga1-xZnx)(N1-xOx) are examined by scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy. RuO2 is an effective cocatalyst that enhances the activity of (Ga1-xZnx)(N1-xOx) for overall water splitting under visible-light irradiation. The highest photocatalytic activity is obtained for a sample loaded with 5.0 wt % RuO2 from an Ru3(CO)12 precursor followed by calcination at 623 K. Calcination is shown to cause the decomposition of initial Ru3(CO)12 on the (Ga1-xZnx)(N1-xOx) surface (373 K) to form Ru(IV) species (423 K). Amorphous RuO2 nanoclusters are then formed by an agglomeration of finer particles (523 K), and the nanoclusters finally crystallize (623 K) to provide the highest catalytic activity. The enhancement of catalytic activity by Ru loading from Ru3(CO)12 is thus shown to be dependent on the formation of crystalline RuO2 nanoparticles with optimal size and coverage.
109 citations
TL;DR: The crystal structure and optical properties of (Ga0.87Zn0.13)(N0.83O0.16) were investigated in this article, showing that oxygen substitutes for nitrogen in the crystal structure, and may be responsible for the desirable optical properties.
79 citations