Kiyotaka Asakura

NiO-loaded NaTaO(3) doped with lanthanum showed a high photocatalytic activity for water splitting into H(2) and O(2) in a stoichiometric amount under UV irradiation. The photocatalytic activity of NiO-loaded NaTaO(3) doped with lanthanum was 9 times higher than that of nondoped NiO-loaded NaTaO(3). The maximum apparent quantum yield of the NiO/NaTaO(3):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 NaTaO(3):La crystals (0.1-0.7 microm) were smaller than that of the nondoped NaTaO(3) crystal (2-3 microm) 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 microscope observations and extended X-ray absorption fine structure analyses indicated that NiO cocatalysts were loaded on the edge of the nanostep structure of NaTaO(3):La photocatalysts as ultrafine particles. The H(2) evolution proceeded on the ultrafine NiO particles loaded on the edge while the O(2) evolution occurred at the groove of the nanostep structure. Thus, the reaction sites for H(2) evolution were separated from those of O(2) evolution over the ordered nanostep structure. 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).

Addition of alkali metal ions significantly promotes the activity of the Pt/TiO2 catalyst for the HCHO oxidation reaction by stabilizing an atomically dispersed Pt-O(OH)x alkali metal species and opening a new low-temperature reaction pathway. The atomically dispersed Na-Pt-O(OH)x species can effectively activate H2O and catalyze the facile reaction between surface OH and formate species to total oxidation products.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCatalytic activity and structural analysis of polymer-protected gold-palladium bimetallic clusters prepared by the simultaneous reduction of hydrogen tetrachloroaurate and palladium dichlorideNaoki Toshima, Masafumi Harada, Yoshinao Yamazaki, and Kiyotaka AsakuraCite this: J. Phys. Chem. 1992, 96, 24, 9927–9933Publication Date (Print):November 1, 1992Publication History Published online1 May 2002Published inissue 1 November 1992https://pubs.acs.org/doi/10.1021/j100203a064https://doi.org/10.1021/j100203a064research-articleACS PublicationsRequest reuse permissionsArticle Views1825Altmetric-Citations333LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options Get e-Alerts

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStructural analysis of polymer-protected palladium/platinum bimetallic clusters as dispersed catalysts by using extended x-ray absorption fine structure spectroscopyNaoki Toshima, Masafumi Harada, Tetsu Yonezawa, Kakuta Kushihashi, and Kiyotaka AsakuraCite this: J. Phys. Chem. 1991, 95, 19, 7448–7453Publication Date (Print):September 1, 1991Publication History Published online1 May 2002Published inissue 1 September 1991https://pubs.acs.org/doi/10.1021/j100172a061https://doi.org/10.1021/j100172a061research-articleACS PublicationsRequest reuse permissionsArticle Views1607Altmetric-Citations287LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options Get e-Alerts

Well-dispersed and stable colloidal dispersions of polymer-protected Ni/Pd bimetallic nanoclusters have been obtained over an entire composition range by an improved polyol reduction method, in which nickel(II) sulfate and palladium(II) acetate were reduced at high temperature by ethylene glycol in the presence of poly(N-vinyl-2-pyrrolidone). Transmission electron microscopy indicates that these bimetallic nanocluster particles have definitely monodispersed size-distributions, with each particle containing both nickel and palladium atoms. The alloy structure has also been shown by X-ray diffraction and extended X-ray absorption fine-structure analysis. X-ray absorption near-edge spectroscopic and X-ray photoelectron spectroscopic data have confirmed that the nickel in the bimetallic nanoclusters is in the zero-valence state, as stabilized by the presence of Pd. Dispersions of these bimetallic nanoclusters were used as homogeneous catalysts for hydrogenation of nitrobenzene at 30 °C under an atmospheric pressure of hydrogen. The catalytic activities are demonstrated to be dependent on the metal composition of the particles. The highest activity can be achieved for a bimetallic nanocluster with a molar ratio of Ni:Pd = 2:3, which exhibits 3.5 times greater activity than that of a typical colloidal palladium catalyst.