Photocatalytic reduction of nitrate ions over tantalate photocatalysts
29 May 2002-Physical Chemistry Chemical Physics (The Royal Society of Chemistry)-Vol. 4, Iss: 12, pp 2833-2838
TL;DR: Tantalate photocatalysts reduced nitrate ions to nitrite ions, dinitrogen, and ammonia under UV irradiation even without co-catalysts or reducing reagents such as organic compounds as discussed by the authors.
Abstract: Tantalate photocatalysts reduced nitrate ions to nitrite ions, dinitrogen, and ammonia under UV irradiation even without co-catalysts or reducing reagents such as organic compounds. The photocatalytic activities of tantalate photocatalysts were larger than those of TiO2 photocatalysts. The selectivity for the photocatalytic reduction of nitrate ions was affected by the addition of co-catalysts. In particular, the efficiencies of dinitrogen and ammonia formation increased by one to two orders of magnitude when a Ni co-catalyst was loaded. The selectivity was also affected by the amount of loaded Ni and the loading method. 44% and 39% of nitrate ions in an aqueous KNO3 solution (0.010 mol L−1, 400 mL) were reduced to dinitrogen and ammonia, respectively, over the Ni(1 wt.%)/KTaO3 photocatalyst after 25 h irradiation.
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TL;DR: This critical review shows the basis of photocatalytic water splitting and experimental points, and surveys heterogeneous photocatalyst materials for water splitting into H2 and O2, and H2 or O2 evolution from an aqueous solution containing a sacrificial reagent.
Abstract: This critical review shows the basis of photocatalytic water splitting and experimental points, and surveys heterogeneous photocatalyst materials for water splitting into H2 and O2, and H2 or O2 evolution from an aqueous solution containing a sacrificial reagent Many oxides consisting of metal cations with d0 and d10 configurations, metal (oxy)sulfide and metal (oxy)nitride photocatalysts have been reported, especially during the latest decade The fruitful photocatalyst library gives important information on factors affecting photocatalytic performances and design of new materials Photocatalytic water splitting and H2 evolution using abundant compounds as electron donors are expected to contribute to construction of a clean and simple system for solar hydrogen production, and a solution of global energy and environmental issues in the future (361 references)
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TL;DR: The small particle size and the ordered surface nanostep structure of the NiO/NaTaO(3):La photocatalyst powder contributed to the highly efficient water splitting into H(2) and O(2).
Abstract: NiO-loaded NaTaO3 doped with lanthanum showed a high photocatalytic activity for water splitting into H2 and O2 in a stoichiometric amount under UV irradiation. The photocatalytic activity of NiO-loaded NaTaO3 doped with lanthanum was 9 times higher than that of nondoped NiO-loaded NaTaO3. The maximum apparent quantum yield of the NiO/NaTaO3:La photocatalyst was 56% at 270 nm. The factors affecting the highly efficient photocatalytic water splitting were examined by using various characterization techniques. Electron microscope observations revealed that the particle sizes of NaTaO3:La crystals (0.1−0.7 μm) were smaller than that of the nondoped NaTaO3 crystal (2−3 μm) and that the ordered surface nanostructure with many characteristic steps was created by the lanthanum doping. The small particle size with a high crystallinity was advantageous to an increase in the probability of the reaction of photogenerated electrons and holes with water molecules toward the recombination. Transmission electron microsc...
1,548 citations
TL;DR: In this paper, a NiO (0.2 wt %)/NaTaO3:La (2%) photocatalyst with a 4.1-eV band gap showed high activity for water splitting.
Abstract: Photocatalysts for water splitting developed by the present authors are reviewed. A NiO (0.2 wt %)/NaTaO3:La (2%) photocatalyst with a 4.1-eV band gap showed high activity for water splitting into ...
378 citations
TL;DR: In this paper, the ABO3-based photocatalysts for water splitting were systematically reviewed in detail and divided into four groups based on the employed modification strategies, i.e., chemical component adjustment, micro-/nano-structure adjustment, local lattice structure adjustment, and application of the modification strategy of ABO 3 in designing AxByOz photocatalyst.
223 citations
01 Jan 2012
TL;DR: In this paper, the ABO3-based photocatalysts for water splitting were systematically reviewed in detail and divided into four groups based on the employed modification strategies, i.e., chemical component adjustment, micro-/nano-structure adjustment, local lattice structure adjustment, and application of the modification strategy of ABO 3 photocatalyst in designing AxByOz photocatylsts.
Abstract: Abstract ABO3-based photocatalysts for water splitting were systematically reviewed in this manuscript. Crystal structure and chemical composition characteristics of ABO3 materials were briefly introduced to guide the modification of ABO3-based photocatalysts. The ABO3-based photocatalysts were then reviewed in detail and divided into four groups based on the employed modification strategies, i.e., chemical component adjustment, micro-/nano-structure adjustment, local lattice structure adjustment, and application of the modification strategy of ABO3 photocatalysts in designing AxByOz photocatalysts. In this section, the recent research works on ABO3-based photocatalysts in our group were presented. Finally, application of ABO3 photocatalysts in Z-scheme systems for overall water splitting was introduced. This review summarized the development of ABO3-based photocatalysts and showed the values and possible direction of future research, thereby offering a guide for photocatalytic water splitting.
174 citations
Additional excerpts
...1 M KNO3 1 wt% Ni/300 1 wt% Ni/480 – [47] (2002) AgTaO3 (0....
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References
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TL;DR: In this paper, the perovskite-like structure of ATaO3 photocatalysts was investigated for water splitting into H2 and O2 under UV irradiation, and it was shown that the excess alkali in the preparation increased the crystal size of NaTaO3 formed and prevented formation of alkali defects in the powder by volatilization.
Abstract: Alkali tantalate ATaO3 (A = Li, Na, and K) photocatalysts with perovskite-like structure showed activities for water splitting into H2 and O2 under UV irradiation. When the alkali tantalates were prepared in the presence of excess alkali, their activities were increased by 1 to 2 orders of magnitude. Scanning electron microscopy and photoluminescence measurements indicated that the excess alkali in the preparation increased the crystal size of NaTaO3 formed and prevented formation of alkali defects in NaTaO3 powder by volatilization, resulting in an increase in the photocatalytic activity. A LiTaO3 photocatalyst showed the highest activity among the naked alkali tantalate photocatalysts prepared in the presence of excess alkali. On the other hand, the activity of a NaTaO3 photocatalyst was increased by 1 order of magnitude when a NiO cocatalyst was loaded. The NiO(0.05 wt %)/NaTaO3 photocatalyst produced H2 and O2 from pure water with rates of 3.39 and 1.58 mmol h-1, respectively. The apparent quantum yie...
592 citations
TL;DR: In this article, the photocatalytic properties of various tantalates were investigated for the decomposition of distilled water into H2 and O2 without co-catalysts.
367 citations
TL;DR: The structure of NiO-SrTiO/sub 3/ powder has been studied by spectroscopic methods such as SEM, TEM, EXAFS, XANES, and XPS as mentioned in this paper.
Abstract: The structure of NiO-SrTiO/sub 3/ powder, which is a photocatalyst for the decomposition of water into H/sub 2/ and O/sub 2/, has been studied by spectroscopic methods such as SEM, TEM, EXAFS, XANES, and XPS. It has been clearly shown that the active catalyst has a peculiar structure; that is, nickel metal exists at the interface of NiO and SrTiO/sub 3/. The surface of NiO changes further into Ni(OH)/sub 2/ during the photocatalytic reaction in water. 31 references, 7 figures, 2 tables.
343 citations
TL;DR: In this article, the authors showed that the performance of NiO/NaTaOO3 photocatalysts was improved by doping of lanthanides, La, Pr, Nd, Sm, Gd, Tb and Dy into NaTaO3.
287 citations
TL;DR: Using oxalic acid as a hole scavenger, the photocatalytic reduction of nitrate in aqueous dispersions of TiO 2 has been investigated in this article, where the effects of concentrations of nitrates, of oxalate, and of pH were studied.
Abstract: Using oxalic acid as a hole scavenger, the photocatalytic reduction of nitrate in aqueous dispersions of TiO 2 has been investigated. Oxalic acid accelerates the reaction considerably compared to the reaction in the absence of oxalic acid. In the presence of nitrate, the oxidation of oxalate is also accelerated. The reduction product of the nitrate is mainly ammonia. The effects of concentrations of nitrate, of oxalate, and of pH were studied. The adsorption of the reactants on TiO 2 is an important factor for accelerating the reaction.
107 citations