Photocatalytic production of hydrogen from biomass-derived feedstocks

The homogeneous (single-cluster) and inhomogeneous contributions to the low temperature electronic absorption spectrum of 35-50 ? diameter CdSe clusters are separated using transient photophysical hole burning. The clusters have the cubic bulk crystal structure, but their electronic states are strongly quantum confined. The inhomogeneous broadening of these features arises because the spectrum depends upon cluster size and shape, and the samples contain similar, but not identical, clusters. The homogeneous spectrum, which consists of a peak 140 cm -1 (17 meV) wide, with a phonon sideband and continuum absorption to higher energy, is compared to a simple molecular orbital model. Electron-vibration coupling, which is enhanced in small clusters, contributes to the substantial broadening of the homogeneous spectrum. The inhomogeneous width of the lowest allowed optical transition was found to be 940 cm -1 , or seven times the homogeneous width, in the most monodisperse sample.

Electronic states of semiconductor clusters : Homogeneous and inhomogeneous broadening of the optical spectrum

Hydrogen trititanate (H2Ti3O7) nanofibers were prepared by a hydrothermal method in 10 M NaOH at 403 K, followed by acidic rinsing and drying at 383 K. Calcining H2Ti3O7 nanofibers at 573 K led to the formation of TiO2 (B) nanofibers. Calcination at 673 K improved the crystallinity of the TiO2 (B) nanofibers and did not cause any change in the morphology and dimensions of the nanofibers. TiO2 (B) and H2Ti3O7 nanofibers are 10−20 nm in diameter and several micrometers long, but FE-SEM reveals that several of these nanofibers tend to bind tightly to each other, forming a fiber bundle. Calcination at 773 K transformed TiO2 (B) nanofibers into a TiO2 (B)/anatase bicrystalline mixture with their fibrous morphology remaining intact. Upon increasing the calcination temperature to 873 K, most of the TiO2 (B) nanofibers were converted into anatase nanofibers and small anatase particles with smoother surfaces. In the photocatalytic dehydrogenation of neat ethanol, 1% Pt/TiO2 (B) nanofiber calcined at 673 K was the ...

Effect of calcination temperature on the structure of a Pt/TiO2 (B) nanofiber and its photocatalytic activity in generating H2.

Catalysis for Selected C1 Chemistry

The modulation of TiO2 structure can effectively alter the oxidation kinetics and pathway of sacrificial ethanol during the water-splitting reaction and dramatically adjust the selectivity of the valuable coupling product 2,3-butanediol from 0.0% to 96.6%, showing the possibility of photohydrogen production in green and economical indexes.

Selective oxidation of sacrificial ethanol over TiO2-based photocatalysts during water splitting

The search for a more efficient production of hydrogen and ethylene glycol from aqueous methanol solution in the presence of ZnS colloid and UV irradiation is reported. The yields of hydrogen and ethylene glycol and the selectivity of ethylene glycol are strongly dependent on the initial pH and the reaction temperature. The selectivity of ethylene glycol can reach 95%. Spin trapping was employed to detect the radical intermediates formed during in situ irradiation of ZnS in aqueous methanol solution. Phenyl- N - tert -butyl nitrone (PBN) can be used as a spin trap. It was confirmed that CH 2 OH is the major radical intermediate in the alkaline reaction system. The coupling of CH 2 OH is the main method of formation of ethylene glycol.

Highly efficient hydrogen and ethylene glycol photoproduction from aqueous methanol solution by ZnS and an in situ spin trapping investigation

Preparation and characterization of ultrafine zinc sulfide particles of quantum confinement

Direct photoproduction of hydrogen and 1,2-propanediol from aqueous methanol and ethanol solution, catalysed by ZnS, has been achieved. Treatment of the catalyst and the reaction temperature have an important influence on the selectivity of the desired product. γ—γ radical cross coupling of CH2OH and CHOHCH3 has been proposed to lead to the formation of 1,2-propanediol. Electron transfer, aldehyde addition reaction and hydrogen atom abstraction also lead to 1,2-propanediol formation.

Xiangwei Zhu

Papers

Highly efficient hydrogen and ethylene glycol photoproduction from aqueous methanol solution by ZnS and an in situ spin trapping investigation

Preparation and characterization of ultrafine zinc sulfide particles of quantum confinement

Photoproduction of hydrogen and 1,2-propanediol from aqueous methanol and ethanol solution catalysed by ZnS

Near-field coupling and wireless signal transmission using a magnetoelectric laminated composite antenna

High-performance floating-gate organic phototransistors based on n-type core-expanded naphthalene diimides