synthesis-catalytic-performance-gold-intercalated-walls-mesoporous

Synthesis and Catalytic Performance of Gold Intercalated in the Walls of Mesoporous Silica

As a promising catalytically active nano reactor, gold nanoparticles intercalated in mesoporous silica (GMS) were successfully synthesized and properties ...

A technique based on the back scattering phenomenon of dynamic light scattering has been employed to monitor the kinetics of gold and platinum metal nanoparticle growth and silver nanoparticle oxidation as well as in the determination of particle sizes ranging from 1 to 200 nm in diameter. The systems were chosen to examine the applicability of dynamic light scattering to nanoresearch over a broad range of sizes as well as both metallic and nonmetallic systems. The advantages of this instrumentation over traditional instruments such as X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) have been highlighted.

In situ approaches to establish colloidal growth kinetics.

In-situ-Ans&#xE4;tze festzustellen kolloidalen Wachstumskinetik.

The tetrairon(III)-substituted polytungstates [Fe(4)(H(2)O)(10)(beta-XW(9)O(33))(2)](n-) (n = 6, X = As(III), Sb(III); n = 4, X = Se(IV), Te(IV)) were immobilized on (3-aminopropyl)triethoxysilane-modified SBA-15 and showed an excellent catalytic performance for solvent-free aerobic oxidation of long-chain n-alkanes using air as the oxidant under ambient conditions through a classical free-radical chain autoxidation mechanism.

Solvent-free aerobic oxidation of n-alkane by iron(III)-substituted polyoxotungstates immobilized on SBA-15.

Die Tetrairon (III)-ersetzt Polytungstates [Fe(4)(H(2)O)(10)(beta-XW(9)O(33))(2)](n-) (n = 6, X = As(III), Sb(III); n = 4, X = Se(IV), Te(IV)) waren auf (3-Aminopropyl-) Triethoxysilane-&Auml;nderungsdatum SBA-15 stillgestellt und zeigten eine hervorragende katalytische Leistung f&uuml;r l&ouml;semittelfreie aerobe Oxidation von langkettigen n-Alkane mit Luft als Oxidationsmittel unter Umgebungsbedingungen durch einen klassischen freie Radikale Kette Autoxidation Mechanismus.

L&ouml;semittelfreie aerobe Oxidation von n-Alkan von Eisen (III)-Polyoxotungstates immobilisiert auf SBA-15 ersetzt.

Nanoscale iron-doped zirconia solid-solution aerogels are prepared via a simple ethanol thermal route using zirconyl nitrate and iron nitrate as starting materials, followed by a supercritical fluid drying process. Structural characteristics are investigated by means of powder X-ray diffraction (XRD), thermal analyses (TG/DTA), N(2) adsorption measurements and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The results show that the resulting iron-doped solid solutions are metastable tetragonal zirconia which exhibit excellent dispersibility and high solubility of iron oxide. Further, when the Fe:(Fe+Zr) ratio x is lower than 0.10, all of the Fe(3+) ions can be incorporated into ZrO(2) by substituting Zr(4+) to form Zr(1-) (x)Fe(x)O(y) solid solutions. Moreover, for the first time, an additional hydroxyl group band that is not present in pure ZrO(2) is observed by DRIFTS for the Zr(Fe)O(2) solid solution. This is direct evidence of Fe(3+) ions incorporated into ZrO(2). These Zr(1-) (x)Fe(x)O(y) solid solutions are excellent catalysts for the solvent-free aerobic oxidation of n-hexadecane using air as the oxidant under ambient conditions. The Zr(0.8)Fe(0.2)O(y) solid-solution catalyst demonstrates the best catalytic properties, with the conversion of n-hexadecane reaching 36.2 % with 48 % selectivity for ketones and 24 % selectivity for alcohols and it can be recycled five times without significant loss of activity.

Catalytic properties of nanoscale iron-doped zirconia solid-solution aerogels.

Nanoskalige Eisen-dotiertes Zirkonoxid Feste-L&ouml;sung Aerogele sind &uuml;ber eine einfache &Auml;thanol-thermische-Route, die mithilfe von Zirconyl Nitrat und Eisen Nitrat als Ausgangsstoffe, gefolgt von einer &uuml;berkritischen Fl&uuml;ssigkeit Trocknung bereit. Strukturelle Merkmale werden mittels Pulver R&ouml;ntgendiffraktometrie (XRD), thermische Analysen (TG/DTA), f&ouml;rmlich Adsorption Messungen untersucht und diffuse Reflexion Fourier Transform Infrarotspektroskopie (DRIFTS). Die Ergebnisse zeigen, dass die resultierende Eisen-dotiertes Feste L&ouml;sungen metastabile Tetragonale Zirkonoxid sind die weisen ausgezeichnete Dispergierbarkeit und hohe L&ouml;slichkeit von Eisenoxid. Weitere, wann das Fe:(Fe+Zr) Verh&auml;ltnis X ist weniger als 0,10, aller Fe(3+) Ionen k&ouml;nnen in ZrO(2) integriert werden, mit der Ma&szlig;gabe Zr(4+) Form Zr(1-) (x)Fe(x)O(y) Solid Solutions. Dar&uuml;ber hinaus wird zum ersten Mal eine zus&auml;tzliche Hydroxyl-Gruppe-Band, die nicht im reinen ZrO(2) ist von DRIFTS f&uuml;r die Zr(Fe)O(2) feste L&ouml;sung beobachtet. Dies ist ein direkter Beweis Fe(3+) Ionen in ZrO(2) integriert. Diese Zr(1-) (x)Fe(x)O(y) Feste L&ouml;sungen sind hervorragende Katalysatoren f&uuml;r l&ouml;semittelfreie aerobe Oxidation von n-Hexadecan mit Luft als Oxidationsmittel unter Umgebungsbedingungen. Der Zr(0.8)Fe(0.2)O(y)-feste-L&ouml;sung-Katalysator zeigt die besten katalytischen Eigenschaften, mit der Umwandlung von n-Hexadecan reichende 36,2 % mit 48 % Selektivit&auml;t f&uuml;r Ketone und 24 % Selektivit&auml;t f&uuml;r Alkohole, und es kann f&uuml;nf Mal ohne einen erheblichen Verlust der Aktivit&auml;t recycelt werden.

Katalytischen Eigenschaften von nanoskaligen Eisen-dotiertes Zirkonoxid Feste-L&ouml;sung Aerogele.

The selective oxidation of alkanes as a green process remains a challenging task because partial oxidation is easier to achieve with sacrificial oxidants, such as hydrogen peroxide, alkyl hydroperoxides or iodosylbenzene, than with molecular oxygen or air. Here, we report on a heterogeneous catalyst for n-hexadecane oxidation comprised of the wheel shaped Cu20-polyoxotungstate [Cu20Cl(OH)24(H2O)12(P8W48O184)]25- anchored on 3-aminopropyltriethoxysilane (apts)-modified SBA-15. The catalysts were characterized by powder X-ray diffraction (XRD), N2-adsorption measurements and Fourier transform infrared reflectance (FT-IR) spectroscopy. The heterogeneous Cu20-polyanion system catalyzed the solvent-free aerobic oxidation of n-hexadecane to alcohols and ketones by using air as the oxidant under ambient conditions. The catalyst exhibits an exceptionally high turn over frequency (TOF) of 20,000 h(-1) at 150 degrees C and is resistant to poisoning by CS2. Moreover, it can be easily recovered and reused by filtration without loss of its catalytic activity. Possible homogeneous contributions also have been examined and eliminated. Thus, this system can use air as oxidant, which, in combination with its good overall performance and poison tolerance, raises the prospect of this type of heterogeneous catalyst for practical applications.

Heterogeneous wheel-shaped Cu20-polyoxotungstate [Cu20Cl(OH)24(H2O)12(P8W48O184)]25- catalyst for solvent-free aerobic oxidation of n-hexadecane.

Die selektive Oxidation von Alkanen als gr&uuml;ne Prozess bleibt eine schwierige Aufgabe, weil partieller Oxidation einfacher mit den opfernden Oxidationsmittel, wie Wasserstoffperoxid, Alkyl Peroxide oder Iodosylbenzene, als mit molekularen Sauerstoff oder Luft zu erreichen ist. Hier berichten wir an einem heterogenen Katalysator f&uuml;r n-Hexadecan Oxydation des Rades umfasste Cu20-Polyoxotungstate [Cu20Cl(OH)24(H2O)12(P8W48O184)] 25 - verankert auf 3-Aminopropyltriethoxysilane (Apts) geformt-SBA-15 ge&auml;ndert. Die Katalysatoren waren gekennzeichnet durch Pulver R&ouml;ntgendiffraktometrie (XRD), N2-Adsorption-Messungen und Fourier-Transform-Infrarot Reflexion (FT-IR) Spektroskopie. Das heterogene Cu20-Polyanion System katalysiert die l&ouml;semittelfreie aerobe Oxidation von n-Hexadecan, Alkohole und Ketone mit Luft als Oxidationsmittel unter Umgebungsbedingungen. Der Katalysator weist eine au&szlig;ergew&ouml;hnlich hohe Wende &uuml;ber Frequenz (TOF) von 20.000 h(-1) bei 150 Grad C und ist resistent gegen Vergiftung durch CS2. Dar&uuml;ber hinaus kann durch Filtration ohne Verlust von seine katalytische Aktivit&auml;t es leicht erholt und wiederverwertet werden. M&ouml;gliche homogene Beitr&auml;ge haben auch untersucht und beseitigt. So k&ouml;nnen dieses System Luft als Oxidationsmittel, die, in Kombination mit guter Gesamtleistung und Gift Toleranz, die Aussicht auf diese Art von heterogenen Katalysator f&uuml;r praktische Anwendungen erh&ouml;ht.

Heterogene Rad-f&ouml;rmigen Cu20-Polyoxotungstate [Cu20Cl(OH)24(H2O)12(P8W48O184)] 25-Katalysator f&uuml;r l&ouml;semittelfreie aerobe Oxidation von n-Hexadecan.

The reaction of [Ru(arene)Cl(2)](2) (arene = benzene, p-cymene) with [X(2)W(22)O(74)(OH)(2)](12-) (X = Sb(III), Bi(III)) in buffer medium resulted in four organo-ruthenium supported heteropolytungstates, [Sb(2)W(20)O(70)(RuC(6)H(6))(2)](10-) (1), [Bi(2)W(20)O(70)(RuC(6)H(6))(2)](10-) (2), [Sb(2)W(20)O(70)(RuC(10)H(14))(2)](10-) (3), and [Bi(2)W(20)O(70)(RuC(10)H(14))(2)](10-) (4), which have been characterized in solution by multinuclear ((183)W, (13)C, (1)H) NMR, UV-vis spectroscopy, electrochemistry, and in the solid state by single-crystal X-ray diffraction, IR spectroscopy, thermogravimetric analysis, and elemental analysis. Polyanions 1, 2, and 4 crystallize in the triclinic system, space group P1 with the following unit cell parameters: K(5)Na(5)[Sb(2)W(20)O(70)(RuC(6)H(6))(2)] x 22 H(2)O (KNa-1), a = 12.1625(2) A, b = 13.1677(2) A, c = 16.0141(3) A, alpha = 78.9201(7) degrees, beta = 74.4442(8) degrees, gamma = 78.9019(8) degrees, and Z = 1; Cs(2)Na(8)[Bi(2)W(20)O(70)(RuC(6)H(6))(2)] x 30 H(2)O (CsNa-2), a = 11.6353(7) A, b = 13.3638(7) A, c = 16.7067(8) A, alpha = 79.568(2) degrees, beta = 71.103(2) degrees, gamma = 80.331(2) degrees, and Z = 1; Na(10)[Bi(2)W(20)O(70)(RuC(10)H(14))(2)].35H(2)O (Na-4), a = 15.7376(12) A, b = 15.9806(13) A, c = 24.2909(19) A, alpha = 92.109(4) degrees, beta = 101.354(4) degrees, gamma = 97.365(3) degrees, and Z = 2. Polyanions 1-4 consist of two (L)Ru(2+) (L = benzene or p-cymene) units linked to a [X(2)W(20)O(70)](14-) (X = Sb(III), Bi(III)) fragment via Ru-O(W) bonds resulting in an assembly with idealized C(2h) symmetry. Polyanions 1-4 are stable in solution as indicated by the expected (183)W, (13)C, and (1)H NMR spectra. The electrochemistry of 1-4 is described by considering the reduction and the oxidation processes. The nature of the arene in Ru(arene) has practically no influence on the formal potentials of the W-centers, which are more sensitive to the Sb or Bi hetero atoms. The results suggest that the respective Sb- and Bi derivatives have very different pK(a) values, with the reduced form of 1 being the most basic, thus permitting the observation of two well-developed voltammetric waves at pH 6. In contrast, the identity of the arene influences the oxidation processes, thus permitting to distinguish them. A strong electrocatalytic water oxidation peak is observed that is more positive than the one corresponding to the Ru(arene) oxidation process. Also a stepwise oxidation of the Ru(benzene) group could be observed at pH 3. The catalytic efficiency, on the other hand, of 1-4 toward the oxidation of n-hexadecane and p-xylene illustrated the effect of ruthenium substitution on the polyanion catalytic performance.

Organo-ruthenium supported heteropolytungstates: synthesis, structure, electrochemistry, and oxidation catalysis.

Die Reaktion von [Ru(arene)Cl(2)](2) (Arene = Benzol, p-Cymen) mit [X(2)W(22)O(74)(OH)(2)](12-) (X = Sb(III), Bi(III)) im Puffer mittlere f&uuml;hrte vier Organo-Ruthenium unterst&uuml;tzt Heteropolytungstates, [Sb(2)W(20)O(70)(RuC(6)H(6))(2)](10-) (1), [Bi(2)W(20)O(70)(RuC(6)H(6))(2)](10-) (2), [Sb(2)W(20)O(70)(RuC(10)H(14))(2)](10-) (3), und [Bi(2)W(20)O(70)(RuC(10)H(14))(2)](10-) (4), die in L&ouml;sung von Multikern ((183) W, (13) C, 1 H) gepr&auml;gt haben NMR, UV-Vis-Spektroskopie, Elektrochemie, und im festen Zustand durch Einzel-Kristall-R&ouml;ntgenbeugung, IR-Spektroskopie, Thermogravimetrische Analyse und Elementaranalyse. Dagegen 1, 2 und 4 im triklinen System kristallisieren Raum Gruppe P1 mit folgenden Parametern Einheit Zelle: K(5)Na(5)[Sb(2)W(20)O(70)(RuC(6)H(6))(2)] x 22 H (2) O (KNa-1), ein = 12.1625(2) A, b = 13.1677(2) A, C = 16.0141(3) A, alpha = 78.9201(7) Grad, Beta = 74.4442(8) Grad, Gamma = 78.9019(8) Grad, und Z = 1; CS(2)na(8)[BI(2)W(20)O(70)(RuC(6)H(6))(2)] X 30 H (2) O (CsNa-2), a = 11.6353(7) A, b = 13.3638(7) A, C = 16.7067(8) A, alpha = 79.568(2) Grad, Beta = 71.103(2) Grad, Gamma = 80.331(2) Grad und Z = 1; Na(10)[BI(2)W(20)O(70)(RuC(10)H(14))(2)] .35h (2) O (Na-4), a = 15.7376(12) A, b = 15.9806(13) A, C = 24.2909(19) A, alpha = 92.109(4) Grad, Beta = 101.354(4) Grad, Gamma = 97.365(3) Grad und Z = 2. Polyanions 1-4 besteht aus zwei (L)Ru(2+) (L = Benzol oder p-Cymol) Einheiten verkn&uuml;pft eine [X(2)W(20)O(70)](14-) (X = Sb(III), Bi(III)) Fragment Ru-O(W)-Bonds, was zu einer Assembly mit idealisierten C(2h) Symmetrie. Polyanions 1-4 sind stabil in L&ouml;sung durch die erwartete (183) W, (13) C und (1) H-NMR-Spektren. Die Elektrochemie der 1-4 wird unter Ber&uuml;cksichtigung der Reduzierung und die Oxidationsprozesse beschrieben. Die Art der Arene in Ru(arene) hat praktisch keinen Einfluss auf die formale Potenziale der W-Zentren, die empfindlicher auf die Sb oder Bi-Hetero-Atomen sind. Die Ergebnisse legen nahe, dass die jeweiligen Sb und Bi-Derivate sehr unterschiedliche pK(a) Werte, mit reduzierter Form 1 als die grundlegendste, so dass die Beobachtung von zwei gut ausgebaute voltammetric Wellen bei pH 6. Im Gegensatz dazu beeinflusst die Identit&auml;t der Arene Oxidationsprozesse, so dass um sie zu unterscheiden. Ein starke elektrokatalytische Wasser Oxydation H&ouml;hepunkt wird beobachtet, ist positiver als die, die Oxidation des Ru(arene) entspricht. Auch konnte eine schrittweise Oxidation der Ru(benzene)-Gruppe bei pH 3 beobachtet werden. Die katalytische Effizienz andererseits, illustriert 1-4 in Richtung Oxidation von n-Hexadecan und p-Xylol die Wirkung von Ruthenium-Substitution auf die Polyanion katalytische Leistung.

Organo-Ruthenium unterst&uuml;tzt Heteropolytungstates: Synthese, Struktur, Elektrochemie und Oxydation Katalyse.

The selective reaction of one part of a bifunctional molecule is a fundamental challenge in heterogeneous catalysis and for many processes including the conversion of biomass-derived intermediates. Selective hydrogenation of unsaturated epoxides to saturated epoxides is particularly difficult given the reactivity of the strained epoxide ring, and traditional platinum group catalysts show low selectivities. We describe the preparation of highly selective Pd catalysts involving the deposition of n-alkanethiol self-assembled monolayer (SAM) coatings. These coatings improve the selectivity of 1-epoxybutane formation from 1-epoxy-3-butene on palladium catalysts from 11 to 94% at equivalent reaction conditions and conversions. Although sulphur species are generally considered to be indiscriminate catalyst poisons, the reaction rate to the desired product on a catalyst coated with a thiol was 40% of the rate on an uncoated catalyst. Interestingly the activity decreased for less-ordered SAMs with shorter chains. The behaviour of SAM-coated catalysts was compared with catalysts where surface sites were modified by carbon monoxide, hydrocarbons or sulphur atoms. The results suggest that the SAMs restrict sulphur coverage to enhance selectivity without significantly poisoning the activity of the desired reaction.

Controlled selectivity for palladium catalysts using self-assembled monolayers.

Die selektive Reaktion eines Teils ein Bifunktionelles Molek&uuml;l ist ein grundlegendes Problem in heterogene Katalyse und f&uuml;r viele Prozesse, einschlie&szlig;lich der Umwandlung von Biomasse abgeleitete Zwischenprodukte. Selektive Hydrierung von unges&auml;ttigten Epoxide, ges&auml;ttigten Epoxide ist besonders schwierig, angesichts die Reaktivit&auml;t des Rings angespannten Epoxid und traditionellen Platin-Gruppe Katalysatoren zeigen niedrige Selektivit&auml;ten. Wir beschreiben die Vorbereitung der hochselektiven Pd-Katalysatoren, die die Ablagerung von n-Alkanethiol assembled Monolayer (SAM) Beschichtungen. Diese Beschichtungen verbessern die Selektivit&auml;t der 1-Epoxybutan-Formation aus 1-Epoxy-3-buten auf Palladium Katalysatoren von 11 bis zu 94 % bei gleichwertigen Reaktionsbedingungen und Konvertierungen. Obwohl Schwefel-Arten im allgemeinen wahllose Katalysatorgifte gelten als, war die Reaktionsgeschwindigkeit auf das gew&uuml;nschte Produkt an einem Katalysator beschichtet mit einem Thiol 40 % des Satzes auf eine unbeschichtete Katalysator. Interessanterweise verringerte Aktivit&auml;t weniger geordnete SAMs mit k&uuml;rzeren Ketten. Das Verhalten von SAM-beschichtete Katalysatoren verglich mit Katalysatoren in der Oberfl&auml;che Websites durch Kohlenmonoxid, Kohlenwasserstoffe oder Schwefel-Atome ver&auml;ndert wurden. Die Ergebnisse legen nahe, dass SAMs Schwefel Abdeckung um die Selektivit&auml;t zu erh&ouml;hen ohne Vergiftung deutlich die Aktivit&auml;t der gew&uuml;nschten Reaktion zu beschr&auml;nken.

Kontrollierte Selektivit&auml;t f&uuml;r Palladium-Katalysatoren mit assembled Monolayers.

A low-temperature ozone exposure technique was employed for the post-treatment of WO(x) nanorod thin films fabricated from hot-wire chemical vapor deposition (HWCVD) and ultrasonic spray deposition (USD) techniques. The resulting films were characterized with x-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, UV-vis-NIR spectroscopy and x-ray photoelectron spectroscopy (XPS). The stoichiometry and surface crystallinity of the WO(x) thin films were subsequently modulated upon ozone exposure and thermal annealing without particle growth. The electrochromic performance was studied in a LiClO(4)-propylene carbonate electrolyte, and the results suggest that the low-temperature ozone exposure technique is superior to the traditional high-temperature thermal annealing (employed to more fully oxidize the WO(x)). The optical modulation at 670 nm was improved from 35% for the as-deposited film to 57% for the film after ozone exposure at 150 °C. The coloration efficiency was improved and the switching speed to the darkened state was significantly accelerated from 18.0 s for the as-deposited film to 11.8 s for the film after the ozone exposure. The process opens an avenue for low-temperature and cost-effective manufacturing of electrochromic films, especially on flexible polymer substrates.

Low-temperature ozone exposure technique to modulate the stoichiometry of WOx nanorods and optimize the electrochromic performance.

Stable gold/mesoporous silica nanocomposites (with Au nanoparticles intercalated in the walls of mesoporous silica) were successfully synthesized by the hydrothermal method and applied as catalysts. A challenging issue associated with intercalation and the use of coordinating agents is the effect of the coordinating agent on the mesoporous silica structure and periodicity. This investigation is targeted at elaborating the effect of the coordinating agent on the resulting mesoporous structure. The amount of Au coordinating agent bis[3-(triethoxysilyl)propyl]-tetrasulfide (TESPTS) was systematically altered to synthesize a range of materials with varying Au loadings and morphologies. These materials were characterized by N(2) adsorption-desorption, x-ray diffraction, transmission electron microscopy and UV-visible spectroscopy. The structures of the catalysts were found to range from mesoporous to vesical- and foam-like upon varying the TESPTS/polymer template (P123) ratio. Additionally, the sizes of Au nanoparticles increased by increasing the amount of TESPTS. The catalytic properties of the resulting materials were examined using oxidation of benzyl alcohol and reduction of 4-nitrophenol as probe reactions. The intercalated systems demonstrated high activity and more importantly were robust and readily reusable. This approach to imparting stability to nanoscale materials may be much more broadly applicable and expand the types of environments in which they can be utilized.

Nanoscale gold intercalated into mesoporous silica as a highly active and robust catalyst.

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) has been used for lipid analysis; however, one of the drawbacks of this technique is matrix interference peaks at low masses. Metal oxide surfaces are described here for direct, matrix-free analysis of small (MW < 1000 Da) lipid compounds, without interferences in the resulting spectra from traditional matrix background peaks. Spectra from lipid standards produced protonated and sodiated molecular ions. More complex mixtures including vegetable oil shortening and lipid extracts from bacterial and algal sources provided similar results. Mechanistic insight into the mode of ionization from surface spectroscopy, negative ion mass spectrometry, and stable isotope studies is also presented. The metal oxide system is compared to other reported matrix-free systems.

Analysis of lipids: metal oxide laser ionization mass spectrometry.

Electrochromic materials exhibit switchable optical properties that can find applications in various fields, including smart windows, nonemissive displays, and semiconductors. High-performing nickel oxide electrochromic materials have been realized by controlling the material composition and tuning the nanostructural morphology. Post-treatment techniques could represent efficient and cost-effective approaches for performance enhancement. Herein, we report on a post-processing ozone technique that improves the electrochromic performance of an aluminum-containing nickel oxide material in lithium-ion electrolytes. The resulting materials were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible-near-infrared (UV-vis-NIR) spectroscopy, and X-ray absorption spectroscopy (XAS). It was observed that ozone exposure increased the Ni oxidation state by introducing hole states in the NiO(6) octahedral unit. In addition, ozone exposure gives rise to higher-performing aluminum-containing nickel oxide films, relative to nickel oxide containing both Al and Li, in terms of switching kinetics, bleached-state transparency, and optical modulation. The improved performance is attributed to the decreased crystallinity and increased nickel oxidation state in aluminum-containing nickel oxide electrochromic films. The present study provides an alternative route to improve electrochromic performance for nickel oxide materials.

Hole doping in Al-containing nickel oxide materials to improve electrochromic performance.

Polyoxometalates (POMs) have demonstrated the unusual ability to both stabilize nanoclusters and facilitate catalytic activity by allowing substrate access to sufficient metallic surface area. This paper presents a wet chemical synthetic method to prepare Pd, Ag, and Au metal nanoclusters stabilized by tetrabutylammonium salts of Phosphotungstates with the well-known Keggin [α-PW(12)O(40)](3-) (PW(12)), Wells-Dawson [P(2)W(18)O(62)](6-) (P(2)W(18)), and their lacunary derivatives [α-PW(11)O(39)](7-) (PW(11)) and [P(2)W(15)O(56)](12-) (P(2)W(15)) structures. The preparation of this series of nanoclusters has facilitated a comparison of the effect these anions have in nanocluster stabilization and catalysis. The nanocluster systems were found to be re-dispersible in acetonitrile and acetone. The effect of aging on stability was followed over 3 months and it was found that many systems were very stable for more than 70 days without precipitation, depending on type of polytungstate stabilizer and the presence of competing ions. The PW(12), P(2)W(18), PW(11), and P(2)W(15) stabilized Pd nanoclusters have been investigated for catalytic activity in the hydrogenation of 1-hexene and were found to be very active with the P(2)W(18) stabilized Pd nanoclusters demonstrating a best of 139,000 Total Turnovers, thus ranking this "soluble heterogeneous catalyst" among one of the longest lived reported in the literature. The nanocluster systems were characterized using instrumental techniques such as UV-Visible Spectroscopy, FTIR Spectroscopy, Powder X-ray Diffraction, Energy Dispersive Spectroscopy, X-ray Photoelectron Spectroscopy, and Transmission Electron Microscopy.

Polyoxotungstate stabilized palladium, gold, and silver nanoclusters: a study of cluster stability, catalysis, and effects of the stabilizing anions.

Electrochromic effects of transition metal oxides provide a great platform for studying lithium intercalation chemistry in solids. Herein, we report on an electronically modified nanocomposite nickel oxide (i.e., Li2.34NiZr0.28Ox) that exhibits significantly improved electrochromic performance relative to the state-of-the-art inorganic electrochromic metal oxides in terms of charge/discharge kinetics, bleached-state transparency, and optical modulation. The knowledge obtained from O K-edge X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) suggests that the internally grown lithium peroxide (i.e., Li2O2) species plays a major role in facilitating charge transfer thus enabling optimal electrochromic performance. This understanding is relevant to recent theoretical studies concerning conductivity in Li2O2 for lithium-air batteries (as cited in the main text). Furthermore, we elucidate the electrochromism in modified nickel oxide in lithium ion electrolyte with the aid of Ni K-edge XAS and Ni L-edge XAS studies. The electrochromism in the nickel oxide materials arises from the reversible formation of hole states on the NiO6 units, which then impacts the Ni oxidation state through the Ni3d-O2p hybridization states. This study sheds light on the lithium intercalation chemistry for general energy storage and semiconductor applications.

Origin of electrochromism in high-performing nanocomposite nickel oxide.

The performance of battery materials is largely governed by structural and chemical evolutions during electrochemical reactions. Therefore, resolving spatially dependent reaction pathways could enlighten mechanistic understanding, and enable rational design for rechargeable battery materials. Here, we present a phase evolution panorama via spectroscopic and three-dimensional imaging at multiple states of charge for an anode material (that is, nickel oxide nanosheets) in lithium-ion batteries. We reconstruct the three-dimensional lithiation/delithiation fronts and find that, in a fully electrolyte immersion environment, phase conversion can nucleate from spatially distant locations on the same slab of material. In addition, the architecture of a lithiated nickel oxide is a bent porous metallic framework. Furthermore, anode-electrolyte interphase is found to be dynamically evolving upon charging and discharging. The present study has implications for resolving the inhomogeneity of the general electrochemically driven phase transition (for example, intercalation reactions) and for the origin of inhomogeneous charge distribution in large-format battery electrodes.

Phase evolution for conversion reaction electrodes in lithium-ion batteries.

The design and synthesis of shape-directed nanoscale noble metal particles have attracted much attention due to their enhanced catalytic properties and the opportunities to study fundamental aspects of nanoscale systems. As such, numerous methods have been developed to synthesize crystals with tunable shapes, sizes, and facets by adding foreign species that promote or restrict growth on specific sites. Many hypotheses regarding how and why certain species direct growth have been put forward, however there has been no consensus on a unifying mechanism of nanocrystal growth. Herein, we develop and demonstrate the capabilities of a mathematical growth model for predicting metal nanoparticle shapes by studying a well known procedure that employs AgNO3 to produce {111} faceted Pt nanocrystals. The insight gained about the role of auxiliary species is then utilized to predict the shape of Pd nanocrystals and to corroborate other shape-directing syntheses reported in literature. The fundamental understanding obtained herein by combining modeling with experimentation is a step toward computationally guided syntheses and, in principle, applicable to predictive design of the growth of crystalline solids at all length scales (nano to bulk).

Shape-directional growth of Pt and Pd nanoparticles.

Nanoparticle electrodes in lithium-ion batteries have both near-surface and interior contributions to their redox capacity, each with distinct rate capabilities. Using combined electron microscopy, synchrotron X-ray methods and ab initio calculations, we have investigated the lithiation pathways that occur in NiO electrodes. We find that the near-surface electroactive (Ni(2+) → Ni(0)) sites saturated very quickly, and then encounter unexpected difficulty in propagating the phase transition into the electrode (referred to as a "shrinking-core" mode). However, the interior capacity for Ni(2+) → Ni(0) can be accessed efficiently following the nucleation of lithiation "fingers" that propagate into the sample bulk, but only after a certain incubation time. Our microstructural observations of the transition from a slow shrinking-core mode to a faster lithiation finger mode corroborate with synchrotron characterization of large-format batteries and can be rationalized by stress effects on transport at high-rate discharge. The finite incubation time of the lithiation fingers sets the intrinsic limitation for the rate capability (and thus the power) of NiO for electrochemical energy storage devices. The present work unravels the link between the nanoscale reaction pathways and the C-rate-dependent capacity loss and provides guidance for the further design of battery materials that favors high C-rate charging.

Transitions from near-surface to interior redox upon lithiation in conversion electrode materials.

This study presents an interfacial modification strategy to improve the performance of electrochromic films that were fabricated by a magnetron sputtering technique. High-quality graphene sheets, synthesized by chemical vapor deposition, were used to modify fluorine-doped tin oxide substrates, followed by the deposition of high-performance nanocomposite nickel oxide electrochromic films. Electrochromic cycling results revealed that a near-complete monolayer graphene interfacial layer improves the electrochromic performance in terms of switching kinetics, activation period, coloration efficiency, and bleached-state transparency, while maintaining ∼100% charge reversibility. The present study offers an alternative route for improving the interfacial properties between electrochromic and transparent conducting oxide films without relying on conventional methods such as nanostructuring or thin film composition control.

Article	Year
In situ approaches to establish colloidal growth kinetics. Journal of colloid and interface science\| PubMed ID: 15464811	2004
Solvent-free aerobic oxidation of n-alkane by iron(III)-substituted polyoxotungstates immobilized on SBA-15. Inorganic chemistry\| PubMed ID: 17854179	2007
Catalytic properties of nanoscale iron-doped zirconia solid-solution aerogels. Chemphyschem : a European journal of chemical physics and physical chemistry\| PubMed ID: 18404744	2008
Heterogeneous wheel-shaped Cu20-polyoxotungstate [Cu20Cl(OH)24(H2O)12(P8W48O184)]25- catalyst for solvent-free aerobic oxidation of n-hexadecane. Chemistry (Weinheim an der Bergstrasse, Germany)\| PubMed ID: 19551774	2009
Organo-ruthenium supported heteropolytungstates: synthesis, structure, electrochemistry, and oxidation catalysis. Inorganic chemistry\| PubMed ID: 19780533	2009
Controlled selectivity for palladium catalysts using self-assembled monolayers. Nature materials\| PubMed ID: 20835234	2010
Low-temperature ozone exposure technique to modulate the stoichiometry of WOx nanorods and optimize the electrochromic performance. Nanotechnology\| PubMed ID: 22653083	2012
Nanoscale gold intercalated into mesoporous silica as a highly active and robust catalyst. Nanotechnology\| PubMed ID: 22744155	2012
Analysis of lipids: metal oxide laser ionization mass spectrometry. Analytical chemistry\| PubMed ID: 22873784	2012
Hole doping in Al-containing nickel oxide materials to improve electrochromic performance. ACS applied materials & interfaces\| PubMed ID: 23249159	2013
Polyoxotungstate stabilized palladium, gold, and silver nanoclusters: a study of cluster stability, catalysis, and effects of the stabilizing anions. Journal of colloid and interface science\| PubMed ID: 23375809	2013
Origin of electrochromism in high-performing nanocomposite nickel oxide. ACS applied materials & interfaces\| PubMed ID: 23547738	2013
Phase evolution for conversion reaction electrodes in lithium-ion batteries. Nature communications\| PubMed ID: 24561888	2014
Shape-directional growth of Pt and Pd nanoparticles. Nanoscale\| PubMed ID: 25142814	2014
Transitions from near-surface to interior redox upon lithiation in conversion electrode materials. Nano letters\| PubMed ID: 25633328	2015
Graphene as an efficient interfacial layer for electrochromic devices. ACS applied materials & interfaces\| PubMed ID: 25950270	2015

Ryan M. Richards

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