Using vacuum ultraviolet photons produced by synchrotron radiation and reflection time-of-flight mass spectrometer, dissociative photoionization of isooctane was measured in the photon energy region of 9.7–15.6 eV under ultrasonic molecular beam. Then the dissociative ionization products at different photon energies were obtained. By measuring the photoionization efficiency curves, the appearance potentials of the dominative ion fragments and the vertical ionization energy of isooctane were determined. In addition, combining with G3 calculations we obtained the structure and energy of the parent, neutral and ion fragments. By comparing the experimental measurements with the theoretical calculations, the dissociative photoionization channels of isooctane were elucidated, and formation enthalpies of the fragmented ions and the dissociation energy of the parent ion were obtained.
Two pure dehydrated borogermanates with microporous structure, β -K 2 [B 2 Ge 3 O 10 ] and NH 4 [BGe 3 O 8 ], have been synthesized and characterized by XRD, FT-IR, TG techniques. The molar enthalpies of solution of 2.51 mg of GeO 2 (s)/0.99 mg of H 3 BO 3 (s)/1.98 mg of H 3 BO 3 (s) in 2.00 cm 3 of 1 mol · dm −3 NaOH (aq) were measured, respectively. The molar enthalpies of solution of 2.44 mg of K 2 B 4 O 7 · 4H 2 O (s) and 2.18 mg of NH 4 B 5 O 8 · 4H 2 O (s) in the mixture solvent of 2.00 cm 3 of 1 mol · dm −3 NaOH (aq) which contains 2.51 mg of GeO 2 (s) were measured, respectively. The molar enthalpies of solution of 3.82 mg of β -K 2 [B 2 Ge 3 O 10 ] (s) in the mixture solvent of 2.00 cm 3 of 1 mol · dm −3 NaOH (aq) which contains 0.99 mg of H 3 BO 3 (s), and 3.00 mg of NH 4 [BGe 3 O 8 ] (s) in the mixture solvent of 2.00 cm 3 of 1 mol · dm −3 NaOH (aq) which contains 1.98 mg of H 3 BO 3 ) (s) were also measured, respectively. With the use of standard molar enthalpies of formation for NH 4 B 5 O 8 · 4H 2 O (s), K 2 B 4 O 7 · 4H 2 O (s), GeO 2 (s), H 3 BO 3 (s) and H 2 O (l), the standard molar enthalpies of formation of – (3937.1 ± 4.7) kJ · mol −1 for β -K 2 [B 2 Ge 3 O 10 ] and – (2713.7 ± 6.0) kJ · mol −1 for NH 4 [BGe 3 O 8 ] at T = 298.15 K were obtained on the basis of the appropriate thermochemical cycles, respectively.
Developing a more effective catalyst for the environmental pollutant is always the pursuit of worldwide researchers. In previous reports, most works were focused on prepared catalysts, and more efforts should explore process from a precursor to the formed catalyst. In this work, V supported TiO 2 catalysts were synthesized with different V loadings, and compared in selective catalytic reduction of nitrogen oxide . For the first time, differential scanning calorimetry was used to analyze the forming enthalpy for these catalysts. As a result, turnover frequency (TOF) was decreased from 0.05 to 0.001 s −1 when the loading was increased from 0.05 to 15 mol%. At the same time, the forming enthalpy was decreased from 16.53 to 1.80 KJ·mol −1 . Spherical Aberration Corrected Transmission Electron Microscope recognized both single-atom and cluster V even at the lowest loading. What’s more, density functional theory revealed that single-atom V had a lower dehydrogenation energy (1.088–1.152 eV) than cluster V during the catalysis (1.834–1.850 eV). According to these evidences, single-atom V had bigger formation enthalpy, lower dehydrogenation energy, and larger TOF than cluster V. These results help to optimize the preparation process for an effective catalyst, which is in favor of hazardous-pollutant treatment.
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