02362nas a2200193   4500008004100000022001400041245014400055210006900199260000800268300001600276490000700292520162800299100002301927700001801950700002201968700001901990700003002009856012902039       2016                        eng d  a1463-907600aAttempt to correlate surface physics and chemical properties : molecular beam and Kelvin probe investigations of Ce 1-x Zr x O 2 thin films0 aAttempt to correlate surface physics and chemical properties mol  cSEP  a27594-276020 v183 a<p>What is the correlation between physical properties of the surfaces (such as surface potential, electronic nature of the surface), and chemical and catalysis properties (such as chemisorption, sticking probability of surface)? An attempt has been made to explore any correlation that might exist between the physical and chemical properties of thin film surfaces. Kelvin probe microscopy (KPM) and the molecular beam (MB) methods were employed to carry out the surface potential, and oxygen adsorption and oxygen storage capacity (OSC) measurements on Ce1−xZrxO2 thin films. A sol–gel synthesis procedure and spin-coating deposition method have been applied to make continuous nanocrystalline Ce1−xZrxO2 (x = 0–1) (CZ) thin films with uniform thickness (35–50 nm); however, surface roughness and porosity inherently changes with CZ composition. MB studies of O2 adsorption on CZ reveal high OSC for Ce0.9Zr0.1O2, which also exhibits highly porous and significantly rough surface characteristics. The surface potential observed from KPM studies varied between 30 and 80 mV, with Ce-rich compositions exhibiting the highest surface potential. Surface potential shows large changes after reduction or oxidation of the CZ film demonstrating the influence of Ce3+/Ce4+ on surface potential, which is also a key to catalytic activity for ceria-based catalysts. The surface potential measured from KPM and the OSC measured from MB vary linearly and they depend on the Ce3+/Ce4+ ratio. More and detailed studies are suggested to arrive at a correlation between the physical and chemical properties of the surfaces.</p>1 aKolekar, Sadhu, K.1 aDubey, Anjani1 aDate, Kalyani, S.1 aDatar, Suwarna1 aGopinath, Chinnakonda, S.  uhttps://library.ncl.res.in/content/attempt-correlate-surface-physics-and-chemical-properties-molecular-beam-and-kelvin-probe01854nas a2200157   4500008004100000245010600041210006900147260000800216300001600224490000600240520125700246100001801503700002301521700003001544856012201574       2016                        eng d00aC-H activation of methane to formaldehyde on Ce1-xZrxO2 thin films: a step to bridge the material gap0 aCH activation of methane to formaldehyde on Ce1xZrxO2 thin films  cDEC  a3650–36560 v83 a<p>Ce1−xZrxO2 (CZ) thin films were prepared by a combination of sol–gel and spin-coating methods and were evaluated for the C−H activation of methane by using a molecular beam set-up with the aim to bridge the material gap. The C−H activation of methane begins at 950 K, and a Ce-rich CZ composition displays a high selectivity (4–12 %) to the partially oxidised product, formaldehyde. A 10–12 % selectivity towards HCHO with 1.6 % methane conversion was observed with methane-rich CH4/O2 reactant compositions at 1050 K. Short contact times, prevalent under molecular beam conditions, could be a possible reason for HCHO formation. Although combustion products were observed instantly upon shining the mixture of reactants on CZ surfaces, up to 20 s delay was observed before formaldehyde generation, which indicates that the oxygen vacancy migration contributes to the rate-determining step and the diffusion-controlled nature of the reaction. A burst in HCHO generation at the point of molecular beam opening, after beam-closed conditions, suggests that the diffusion of oxygen vacancies to the surface is the reason for HCHO formation. Kinetics results also indicate the necessity of reduction sites for HCHO generation.</p>1 aDubey, Anjani1 aKolekar, Sadhu, K.1 aGopinath, Chinnakonda, S.  uhttps://library.ncl.res.in/content/c-h-activation-methane-formaldehyde-ce1-xzrxo2-thin-films-step-bridge-material-gap01545nas a2200157   4500008004100000245008400041210006900125260000800194300001400202490000600216520098800222100001801210700002301228700003001251856010601281       2016                        eng d00aC-H activation of methane to syngas on MnxCe1-x-yZryO2 - a molecular beam study0 aCH activation of methane to syngas on MnxCe1xyZryO2 a molecular   cJUL  a2296-23060 v83 a<p>Mn-doped ceria zirconia thin films (MnxCe1-x-yZryO2, MCZ) were employed as flat model catalyst surfaces for CH4 activation. MCZ films exhibit characteristics of single crystal and powder materials, such as smooth surfaces and porosity. From molecular-beam studies, it has been identified that the oxygen storage capacity increases with Mn content. Mutually exclusive observation of H2O or a mixture of products (CO2+ CO + H-2) occurs, when the reactants was allowed to react directly on MCZ, underscoring their formation or prevention (and consumption), respectively. The results suggest that there is competition and cooperation among different elementary reactions under complementary conditions. From a significant partial oxidation of CH4 through C-H activation, it is found that formation of syngas begins at 700 K and the reaction rate increases with increasing temperature. Kinetic evidences indicate that the reaction proceeds through a combustion-reformation pathway.</p>1 aDubey, Anjani1 aKolekar, Sadhu, K.1 aGopinath, Chinnakonda, S.  uhttps://library.ncl.res.in/content/c-h-activation-methane-syngas-mnxce1-x-yzryo2-molecular-beam-study02572nas a2200181   4500008004100000022001400041245011600055210006900171260011000240300001400350490000600364520180000370100001602170700001802186700002702204700003002231856012902261       2016                        eng d  a2044-475300aGas-solid interaction of H-2-Ce0.95Zr0.05O2: new insights into surface participation in heterogeneous catalysis0 aGassolid interaction of H2Ce095Zr005O2 new insights into surface  aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcOCT  a1746-17560 v63 a<p>A direct interaction between a reduction medium (H-2) and a Ce0.95Zr0.05O2 (CZ) solid surface was explored through ambient pressure photoelectron spectroscopy (APPES), with conventional X-ray and He-I photon sources, in H-2 atmosphere up to 0.1 mbar pressure and 773 K. A porous CZ thin film was prepared by a combination of sol-gel and spin-coating methods, and was employed to understand the redox nature of ceria under reduction conditions. The maximum of 45% Ce3+ along with the corresponding oxygen vacancy was observed due to reduction. An unprecedented decrease in the valence band (VB) energy up to 1.4 eV was observed on reduction along with a narrowing of VB. The highest occupied energy band derived from Ce 4f also shifts closer to E-F. H-2 molecular vibration observed in VB-APPES was employed as a probe to explore the surface potential changes along with the dynamic change in the nature of the surface under reduction conditions. The surface potential decreases by 0.27 eV up to 673 K, and then it reverts by 0.24 eV on further reduction at 773 K for different reasons. Further, an enhancement in the Ce 5d-O 2p interaction occurs at the expense of the Ce 4f-O 2p interaction under the above reduction conditions. Vacuum annealing and H-2 reduction after that show significantly more VB shift and enhanced reduction than H-2 reduction alone. Although Ce reduction occurs on high temperature vacuum annealing of CZ, a significantly lower amount of oxygen vacancies appears. This study shows the dynamic changes in the nature of the surface due to a gas (H-2)-solid (CZ) interaction and ensuing electronic structure changes that influence heterogeneous catalysis. It also underscores the necessity to study the catalytic materials under in situ conditions or closer to that.</p>1 aJain, Ruchi1 aDubey, Anjani1 aGhosalya, Manoj, Kumar1 aGopinath, Chinnakonda, S.  uhttps://library.ncl.res.in/content/gas-solid-interaction-h-2-ce095zr005o2-new-insights-surface-participation-heterogeneous-002106nas a2200193   4500008004100000245008300041210006900124260000800193300000900201490000600210520145500216100001801671700002301689700002601712700001501738700001801753700003001771856011101801       2016                        eng d00aPorous thin films towards bridging the material gap in heterogeneous catalysis0 aPorous thin films towards bridging the material gap in heterogen  cMAR  a1-120 v23 a<p>An attempt has been made to bridge the material gap, existing between ideal single crystals and real-world powder nanocatalyst employed in surface science and heterogeneous catalysis, respectively. Simple wet chemical method (sol–gel and spin-coating deposition) has been applied to make continuous Ce1 − xZrxO2 (x = 0–1) (CZ) thin films with uniform thickness (~40 nm) and smooth surface characteristics. Uniform thickness and surface smoothness of the films over a large area was supported by a variety of measurements. Molecular beam (MB) studies of O2 adsorption on CZ surfaces reveals the oxygen storage capacity (OSC), and sticking coefficient increases from 400 to 800 K. Porous nature of Ce-rich CZ compositions enhances O2 adsorption and OSC, predominantly due to O-diffusion and redox nature, even at 400 K. A good correlation exists between MB measurements made on CZ films for oxygen adsorption, and OSC, and ambient pressure CO oxidation on powder form of CZ; this demonstrates the large potential to bridge the material gap. CZ was particularly chosen as a model system for the present studies, since it has been well-studied and a correlation between surface science properties made on thin films and catalysis on powder CZ materials could be a litmus test. Ambient catalysis on ceria-zirconia nanocatalyst correlates well with surface properties measured through molecular beam on thinfilm and close the material gap.</p>1 aDubey, Anjani1 aKolekar, Sadhu, K.1 aGnanakumar, Edwin, S.1 aRoy, Kanak1 aVinod, C., P.1 aGopinath, Chinnakonda, S.  uhttps://library.ncl.res.in/content/porous-thin-films-towards-bridging-material-gap-heterogeneous-catalysis01365nas a2200145   4500008004100000245009100041210006900132260000800201300001400209520080400223100001801027700002901045700003001074856011501104       2017                        eng d00aAmbient CO oxidation on in-situ generated Co3O4 spinel surfaces with random morphology0 aAmbient CO oxidation on insitu generated Co3O4 spinel surfaces w  cJAN  a431–4323 a<p>The influence of the Co3O4 morphology on its redox behavior and catalytic performance in the CO oxidation reaction is studied. Three different Co3O4 morphologies were synthesized by precipitation and hydrothermal methods. TEM and SEM observations clearly show the different obtained morphologies: rods, wires and a mixture of plates and cubes. The textural properties depend on the morphology and the redox ones on the particle size. XRD analysis reveals a spinel structure in all solids but a preferential exposition of the [110] plane is presented in the Co3O4 rods. This preferential exposition, along with its higher specific surface area provides the rods with more efficient oxygen storage capacity resulting in an excellent catalytic performance compared to the other two morphologies.</p>1 aDubey, Anjani1 aReddy, Kasala, Prabhakar1 aGopinath, Chinnakonda, S.  uhttps://library.ncl.res.in/content/ambient-co-oxidation-situ-generated-co3o4-spinel-surfaces-random-morphology02229nas a2200241   4500008004100000022001400041245010800055210006900163260000800232300000700240490000800247520142000255653001001675653002701685653001901712653001401731653002001745100001801765700002601783700002401809700003001833856012401863       2022                        eng d  a0974-362600aFacile, sustainable and unassisted plain water oxidation on Au/Ce0.9Ti0.1O2 nanorods in direct sunlight0 aFacile sustainable and unassisted plain water oxidation on AuCe0  cJUN  a610 v1343 a<p>
	Impressive rate of solar water oxidation to molecular oxygen (O-2) has been demonstrated on nanorods (NRs) of Ce0.9Ti0.1O2 (CT-NR) and Au-deposited CT-NR (Au-CT-NR) photocatalysts with a sacrificial agent (Fe3+) and in plain water in one sun condition, direct sunlight and with lambda &gt;= 455 nm. Probably the highest 0 2 yield of 11 mmol/h.g was observed with Au-CT-NR thin film in plain water in direct sunlight, with no sacrificial agent or applied potential. Photoelectrochemical measurements demonstrate a marked reduction in oxidation onset potential of Au-CT-NR by 150 mV with stable photocurrent (0.75 mA/cm(2)), compared to CT-NR (0.23 mA/cm(2)), indicating the operative of plasmon-induced resonant energy transfer (PIRET) process. Effective electron quenching by nanogold and hence low recombination in the depletion region is a critical step for the observation of a high rate of oxygen evolution. In addition to this, a predominant change in the nature of the valence band from O-2p dominated on CeO2 to Ce-4f dominated with CT-NR (due to Ti4+ introduction in CeO2), the efficient light absorption of photocatalysts in thin-film form, functional and effective PIRET process, and facile E-F alignment, enhances the oxygen evolution with Au-CT-NR in direct sunlight and make it highly sustainable. A possible mechanism of water oxidation is proposed from the observed experimental findings.</p>
10aceria10aElectronic integration10aPhotocatalysis10athin film10awater splitting1 aDubey, Anjani1 aMishra, Abhaya, Kumar1 aNegi, Sanjay, Singh1 aGopinath, Chinnakonda, S.  uhttps://library.ncl.res.in/content/facile-sustainable-and-unassisted-plain-water-oxidation-auce09ti01o2-nanorods-direct