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Charles T Campbell - One of the best experts on this subject based on the ideXlab platform.
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energetics of formic acid conversion to adsorbed formates on pt 111 by transient calorimetry
Journal of the American Chemical Society, 2014Co-Authors: Trent L Silbaugh, Eric M Karp, Charles T CampbellAbstract:Carboxylates adsorbed on solid surfaces are important in many technological applications, ranging from heterogeneous catalysis and surface organo-functionalization to medical implants. We report here the first experimentally determined enthalpy of formation of any surface bound carboxylate on any surface, formate on Pt(111). This was accomplished by studying the dissociative adsorption of formic acid on oxygen-presaturated (O-sat) Pt(111) to make adsorbed monodentate and bidentate formates using single-crystal adsorption calorimetry. The Integral Heat of molecular adsorption of formic acid on clean Pt(111) at 100 K is 62.5 kJ/mol at 0.25 monolayer (ML). On O-sat Pt(111), the Integral Heat of the dissociative adsorption of formic acid to make monodentate formate (HCOOmon,ad) plus the water–hydroxyl complex ((H2O–OH)ad) was found to be 76 kJ/mol at 3/8 ML and 100–150 K. Similarly, its Integral Heat of dissociative adsorption to make bidentate formate (HCOObi,ad) plus (H2O–OH)ad was 106 kJ/mol at 3/8 ML and ...
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adsorption energy of tert butyl on pt 111 by dissociation of tert butyl iodide calorimetry and dft
Journal of Physical Chemistry C, 2014Co-Authors: Trent L Silbaugh, Javier B Giorgi, Aashani Tillekaratne, Francisco Zaera, Charles T CampbellAbstract:Dissociative and molecular adsorption of tert-butyl iodide on Pt(111) has been studied by single-crystal adsorption calorimetry (SCAC), photoelectron spectroscopy (XPS), reflection/adsorption infrared spectroscopy (RAIRS), and density functional theory (DFT) calculations. Up to a t-BuI total coverage of 0.07 ML, t-BuI adsorbs dissociatively at 100 K to form t-Buad plus Iad, with an Integral Heat of reaction of 223 kJ/mol. At higher coverage, up to a total coverage of 0.15 ML, t-BuI adsorbs molecularly directly to the Pt surface atoms with an average Heat of adsorption of 91 kJ/mol. At 0.15 ML, the first layer is saturated. Between 0.15 and 0.38 ML, t-BuI adsorbs molecularly on top of the first layer with a constant Heat of adsorption of 44.5 ± 1.9 kJ/mol. The standard enthalpy of formation of adsorbed tert-butyl on Pt(111) at 1/25 ML coverage is estimated from the Heat measurements to be −168 ± 20 kJ/mol, giving a (CH3)3C–Pt(111) bond enthalpy of 216 ± 20 kJ/mol. DFT calculations were performed using the ...
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the energy of adsorbed hydroxyl on pt 111 by microcalorimetry
Journal of Physical Chemistry C, 2011Co-Authors: Wanda Lew, Eric M Karp, Matthew C Crowe, Ole Lytken, Jason A Farmer, Liney Arnadottir, Carolyn Schoenbaum, Charles T CampbellAbstract:The energy of adsorbed hydroxyl on Pt(111) was measured by dosing D2O gas onto oxygen precovered Pt(111) at 150 K while following the Heat of reaction with single-crystal adsorption calorimetry. The adsorption of D2O on oxygen precovered Pt(111) is known to produce surface OD (hydroxyl) coadsorbed with molecular D2O in a well-defined structure. The Heat of reaction and sticking probability of D2O on Pt(111) were measured as a function of oxygen precoverage and D2O dose. With 0.25 monolayers (ML) of oxygen atoms, the differential Heat of adsorption is nearly constant at 61.3 kJ/mol for the first ∼1/3 ML but drops to 57.9 kJ/mol by 0.50 ML and 50.5 kJ/mol by saturation (0.62 ML). Similar experiments with Oad precoverages of 0.18 and 0.07 ML gave lower saturation D2O coverages (0.55 and 0.22 ML, respectively) and lower Heats of reaction by ∼3.4 and ∼4.6 kJ/mol, respectively, except at very low D2O coverage where step sites may play a role. From the Integral Heat of D2O adsorption, the standard enthalpy of fo...
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energy of molecularly adsorbed water on clean pt 111 and pt 111 with coadsorbed oxygen by calorimetry
Journal of Physical Chemistry C, 2011Co-Authors: Matthew C Crowe, Eric M Karp, Charles T CampbellAbstract:The Heat of adsorption and sticking probability of D2O were measured on Pt(111) with and without preadsorbed oxygen adatoms as a function of D2O coverage using single-crystal adsorption calorimetry from 88 to 120 K. In this temperature range, water adsorbs molecularly on both surfaces, and, at multilayer coverages, forms amorphous solid water on Pt(111). The Integral Heat of adsorption at a D2O coverage of 0.5 ML on clean Pt(111) was found to be 51.3 ± 1.6 kJ/mol at 120 K, 4.1 kJ/mol larger than in the multilayer. Its change with temperature gives a Heat capacity for the adlayer islands of 130 ± 83 J/(mol K). This Heat of adsorption at 120 K provides a standard enthalpy of formation of adsorbed D2O on Pt(111) of −301 kJ/mol at 120 K and a D2O coverage of 0.5 ML, which we attribute to water islands in the (√37 × √37)R25.3° structure based on prior structural studies. The Integral Heat of molecular adsorption of D2O at 120 K on Pt(111) predosed with 0.25 ML of oxygen adatoms was ∼55.0 kJ/mol at 0.5 ML, 3.7 ...
Trent L Silbaugh - One of the best experts on this subject based on the ideXlab platform.
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energetics of formic acid conversion to adsorbed formates on pt 111 by transient calorimetry
Journal of the American Chemical Society, 2014Co-Authors: Trent L Silbaugh, Eric M Karp, Charles T CampbellAbstract:Carboxylates adsorbed on solid surfaces are important in many technological applications, ranging from heterogeneous catalysis and surface organo-functionalization to medical implants. We report here the first experimentally determined enthalpy of formation of any surface bound carboxylate on any surface, formate on Pt(111). This was accomplished by studying the dissociative adsorption of formic acid on oxygen-presaturated (O-sat) Pt(111) to make adsorbed monodentate and bidentate formates using single-crystal adsorption calorimetry. The Integral Heat of molecular adsorption of formic acid on clean Pt(111) at 100 K is 62.5 kJ/mol at 0.25 monolayer (ML). On O-sat Pt(111), the Integral Heat of the dissociative adsorption of formic acid to make monodentate formate (HCOOmon,ad) plus the water–hydroxyl complex ((H2O–OH)ad) was found to be 76 kJ/mol at 3/8 ML and 100–150 K. Similarly, its Integral Heat of dissociative adsorption to make bidentate formate (HCOObi,ad) plus (H2O–OH)ad was 106 kJ/mol at 3/8 ML and ...
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adsorption energy of tert butyl on pt 111 by dissociation of tert butyl iodide calorimetry and dft
Journal of Physical Chemistry C, 2014Co-Authors: Trent L Silbaugh, Javier B Giorgi, Aashani Tillekaratne, Francisco Zaera, Charles T CampbellAbstract:Dissociative and molecular adsorption of tert-butyl iodide on Pt(111) has been studied by single-crystal adsorption calorimetry (SCAC), photoelectron spectroscopy (XPS), reflection/adsorption infrared spectroscopy (RAIRS), and density functional theory (DFT) calculations. Up to a t-BuI total coverage of 0.07 ML, t-BuI adsorbs dissociatively at 100 K to form t-Buad plus Iad, with an Integral Heat of reaction of 223 kJ/mol. At higher coverage, up to a total coverage of 0.15 ML, t-BuI adsorbs molecularly directly to the Pt surface atoms with an average Heat of adsorption of 91 kJ/mol. At 0.15 ML, the first layer is saturated. Between 0.15 and 0.38 ML, t-BuI adsorbs molecularly on top of the first layer with a constant Heat of adsorption of 44.5 ± 1.9 kJ/mol. The standard enthalpy of formation of adsorbed tert-butyl on Pt(111) at 1/25 ML coverage is estimated from the Heat measurements to be −168 ± 20 kJ/mol, giving a (CH3)3C–Pt(111) bond enthalpy of 216 ± 20 kJ/mol. DFT calculations were performed using the ...
Eric M Karp - One of the best experts on this subject based on the ideXlab platform.
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energetics of formic acid conversion to adsorbed formates on pt 111 by transient calorimetry
Journal of the American Chemical Society, 2014Co-Authors: Trent L Silbaugh, Eric M Karp, Charles T CampbellAbstract:Carboxylates adsorbed on solid surfaces are important in many technological applications, ranging from heterogeneous catalysis and surface organo-functionalization to medical implants. We report here the first experimentally determined enthalpy of formation of any surface bound carboxylate on any surface, formate on Pt(111). This was accomplished by studying the dissociative adsorption of formic acid on oxygen-presaturated (O-sat) Pt(111) to make adsorbed monodentate and bidentate formates using single-crystal adsorption calorimetry. The Integral Heat of molecular adsorption of formic acid on clean Pt(111) at 100 K is 62.5 kJ/mol at 0.25 monolayer (ML). On O-sat Pt(111), the Integral Heat of the dissociative adsorption of formic acid to make monodentate formate (HCOOmon,ad) plus the water–hydroxyl complex ((H2O–OH)ad) was found to be 76 kJ/mol at 3/8 ML and 100–150 K. Similarly, its Integral Heat of dissociative adsorption to make bidentate formate (HCOObi,ad) plus (H2O–OH)ad was 106 kJ/mol at 3/8 ML and ...
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the energy of adsorbed hydroxyl on pt 111 by microcalorimetry
Journal of Physical Chemistry C, 2011Co-Authors: Wanda Lew, Eric M Karp, Matthew C Crowe, Ole Lytken, Jason A Farmer, Liney Arnadottir, Carolyn Schoenbaum, Charles T CampbellAbstract:The energy of adsorbed hydroxyl on Pt(111) was measured by dosing D2O gas onto oxygen precovered Pt(111) at 150 K while following the Heat of reaction with single-crystal adsorption calorimetry. The adsorption of D2O on oxygen precovered Pt(111) is known to produce surface OD (hydroxyl) coadsorbed with molecular D2O in a well-defined structure. The Heat of reaction and sticking probability of D2O on Pt(111) were measured as a function of oxygen precoverage and D2O dose. With 0.25 monolayers (ML) of oxygen atoms, the differential Heat of adsorption is nearly constant at 61.3 kJ/mol for the first ∼1/3 ML but drops to 57.9 kJ/mol by 0.50 ML and 50.5 kJ/mol by saturation (0.62 ML). Similar experiments with Oad precoverages of 0.18 and 0.07 ML gave lower saturation D2O coverages (0.55 and 0.22 ML, respectively) and lower Heats of reaction by ∼3.4 and ∼4.6 kJ/mol, respectively, except at very low D2O coverage where step sites may play a role. From the Integral Heat of D2O adsorption, the standard enthalpy of fo...
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energy of molecularly adsorbed water on clean pt 111 and pt 111 with coadsorbed oxygen by calorimetry
Journal of Physical Chemistry C, 2011Co-Authors: Matthew C Crowe, Eric M Karp, Charles T CampbellAbstract:The Heat of adsorption and sticking probability of D2O were measured on Pt(111) with and without preadsorbed oxygen adatoms as a function of D2O coverage using single-crystal adsorption calorimetry from 88 to 120 K. In this temperature range, water adsorbs molecularly on both surfaces, and, at multilayer coverages, forms amorphous solid water on Pt(111). The Integral Heat of adsorption at a D2O coverage of 0.5 ML on clean Pt(111) was found to be 51.3 ± 1.6 kJ/mol at 120 K, 4.1 kJ/mol larger than in the multilayer. Its change with temperature gives a Heat capacity for the adlayer islands of 130 ± 83 J/(mol K). This Heat of adsorption at 120 K provides a standard enthalpy of formation of adsorbed D2O on Pt(111) of −301 kJ/mol at 120 K and a D2O coverage of 0.5 ML, which we attribute to water islands in the (√37 × √37)R25.3° structure based on prior structural studies. The Integral Heat of molecular adsorption of D2O at 120 K on Pt(111) predosed with 0.25 ML of oxygen adatoms was ∼55.0 kJ/mol at 0.5 ML, 3.7 ...
Matthew C Crowe - One of the best experts on this subject based on the ideXlab platform.
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the energy of adsorbed hydroxyl on pt 111 by microcalorimetry
Journal of Physical Chemistry C, 2011Co-Authors: Wanda Lew, Eric M Karp, Matthew C Crowe, Ole Lytken, Jason A Farmer, Liney Arnadottir, Carolyn Schoenbaum, Charles T CampbellAbstract:The energy of adsorbed hydroxyl on Pt(111) was measured by dosing D2O gas onto oxygen precovered Pt(111) at 150 K while following the Heat of reaction with single-crystal adsorption calorimetry. The adsorption of D2O on oxygen precovered Pt(111) is known to produce surface OD (hydroxyl) coadsorbed with molecular D2O in a well-defined structure. The Heat of reaction and sticking probability of D2O on Pt(111) were measured as a function of oxygen precoverage and D2O dose. With 0.25 monolayers (ML) of oxygen atoms, the differential Heat of adsorption is nearly constant at 61.3 kJ/mol for the first ∼1/3 ML but drops to 57.9 kJ/mol by 0.50 ML and 50.5 kJ/mol by saturation (0.62 ML). Similar experiments with Oad precoverages of 0.18 and 0.07 ML gave lower saturation D2O coverages (0.55 and 0.22 ML, respectively) and lower Heats of reaction by ∼3.4 and ∼4.6 kJ/mol, respectively, except at very low D2O coverage where step sites may play a role. From the Integral Heat of D2O adsorption, the standard enthalpy of fo...
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energy of molecularly adsorbed water on clean pt 111 and pt 111 with coadsorbed oxygen by calorimetry
Journal of Physical Chemistry C, 2011Co-Authors: Matthew C Crowe, Eric M Karp, Charles T CampbellAbstract:The Heat of adsorption and sticking probability of D2O were measured on Pt(111) with and without preadsorbed oxygen adatoms as a function of D2O coverage using single-crystal adsorption calorimetry from 88 to 120 K. In this temperature range, water adsorbs molecularly on both surfaces, and, at multilayer coverages, forms amorphous solid water on Pt(111). The Integral Heat of adsorption at a D2O coverage of 0.5 ML on clean Pt(111) was found to be 51.3 ± 1.6 kJ/mol at 120 K, 4.1 kJ/mol larger than in the multilayer. Its change with temperature gives a Heat capacity for the adlayer islands of 130 ± 83 J/(mol K). This Heat of adsorption at 120 K provides a standard enthalpy of formation of adsorbed D2O on Pt(111) of −301 kJ/mol at 120 K and a D2O coverage of 0.5 ML, which we attribute to water islands in the (√37 × √37)R25.3° structure based on prior structural studies. The Integral Heat of molecular adsorption of D2O at 120 K on Pt(111) predosed with 0.25 ML of oxygen adatoms was ∼55.0 kJ/mol at 0.5 ML, 3.7 ...
Alexandra Navrotsky - One of the best experts on this subject based on the ideXlab platform.
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surface enthalpy and enthalpy of water adsorption of nanocrystalline tin dioxide thermodynamic insight on the sensing activity
Journal of Materials Research, 2011Co-Authors: Ricardo H R Castro, Wei Zhou, Alexandra NavrotskyAbstract:Tin dioxide (SnO 2 ) is an important base material for a variety of gas sensors and catalysts. However, there is a lack of experimental data on the energetics of SnO 2 surfaces and their water adsorption. In this work, the surface energies of anhydrous and hydrated SnO 2 nanoparticles were measured by combining high-temperature oxide melt solution calorimetry and water adsorption calorimetry. The SnO 2 nanoparticles were synthesized through oxidation of metallic tin using nitric acid followed by Heat treatment at different temperatures to achieve surface areas ranging from 4000 to 10,000 m 2 ·mol −1 (25–65 m 2 ·g −1 ). The enthalpy of the anhydrous surface is 1.72 ± 0.01 J·m −2 , and that of the hydrated surface is 1.49 ± 0.01 J·m −2 . The Integral Heat of water adsorption is −75 kJ·mol −1 , with a chemisorbed maximum coverage of ∼5 H 2 O·nm −2 . SnO 2 has a lower surface energy and less exothermic enthalpy of water adsorption than the isostructural TiO 2 (rutile) reported previously. This comparison suggests that the excellent sensing properties of SnO 2 may be a consequence of its relatively low affinity for surface H 2 O molecules that compete with other gases for adsorption.
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study on synthesis of tpa silicalite 1 from initially clear solutions of various base concentrations by in situ calorimetry potentiometry and saxs
Chemistry of Materials, 2004Co-Authors: Sanyuan Yang, Alexandra Navrotsky, David J Wesolowski, John A PopleAbstract:The synthesis process of TPA-silicalite-1 from a series of initially clear solutions (with a general formula based on mole ratios of the components x:25:480:100 TPAOH:SiO2:H2O:C2H5OH, where TPA = tetrapropylammonium, x = 3−13) was investigated using small-angle X-ray scattering (SAXS), in situ calorimetry, and in situ pH measurement. The size of the nanoparticles detected in the initially clear solutions decreases from 8.5 to 2.5 nm as x increases from 3 to 13. Crystal growth from these solutions at 95 °C is first exothermic and then endothermic. The exo−endo thermal switch coincides with a jump in the solution alkalinity. With increasing x the Integral Heat of exothermic crystal growth decreases monotonically from −0.61 kJ/mol (per mole of Si in the mixture) at x = 4 and approaches zero at x = 12. The Integral Heat of endothermic crystal growth increases to approach a plateau (0.26 kJ/mol of Si) at x = 7. Crystal growth is fastest at x = 6−7 and relatively slower at x either higher than 7 or lower than 6...
