We report the use of a simple complex assembled from Ni(II) salt and 2-mecaptoethanol in one step in water as the efficient catalyst in a molecular hydrogen system which can be sensitized by a low-cost xanthene dye, Erythrosin B. An excellent quantum efficiency of 24.5% is attained at 460 nm. This simple system is expected to contribute toward the development of economical and environmentally benign solar hydrogen production systems.
Photocatalytic water splitting is attracting enormous interest for the storage of solar energy but no practical method has yet been identified. In the past decades, various systems have been developed but most of them suffer from low activities, a narrow range of absorption and poor quantum efficiencies (Q.E.) due to fast recombination of charge carriers. Here we report a dramatic suppression of electron-hole pair recombination on the surface of N-doped TiO2 based nanocatalysts under enhanced concentrations of H+ and OH−, and local electric field polarization of a MgO (111) support during photolysis of water at elevated temperatures. Thus, a broad optical absorption is seen, producing O2 and H2 in a 1:2 molar ratio with a H2 evolution rate of over 11,000 μmol g−1 h−1 without any sacrificial reagents at 270 °C. An exceptional range of Q.E. from 81.8% at 437 nm to 3.2% at 1000 nm is also reported.
Replacement of Hg with non-toxic Au based catalysts for industrial hydrochlorination of acetylene to vinyl chloride is urgently required. However Au catalysts suffer from progressive deactivation caused by auto-reduction of Au(I) and Au(III) active sites and irreversible aggregation of Au(0) inactive sites. Here we show from synchrotron X-ray absorption, STEM imaging and DFT modelling that the availability of ceria(110) surface renders Au(0)/Au(I) as active pairs. Thus, Au(0) is directly involved in the catalysis. Owing to the strong mediating properties of Ce(IV)/Ce(III) with one electron complementary redox coupling reactions, the ceria promotion to Au catalysts gives enhanced activity and stability. Total pre-reduction of Au species to inactive Au nanoparticles of Au/CeO2&AC when placed in a C2H2/HCl stream can also rapidly rejuvenate. This is dramatically achieved by re-dispersing the Au particles to Au(0) atoms and oxidising to Au(I) entities, whereas Au/AC does not recover from the deactivation.
A simple and facile template-free method has been developed for the fabrication of CdS hollow nanospheres
via hydrothermal treatment of aqueous solutions of cadmium acetate and thiourea. Based on the detailed
investigation on the influences of experimental parameters including the precursor chemical concentrations,
reaction time, and reaction temperature, the formation mechanism of the hollow interiors by an Ostwald
ripening process was the first time proposed for CdS hollow nanospheres. In particular, it was found that
molar ratio of thiourea:Cd2+ in the starting solutions affected the sizes of the nanospheres and the hollowing
process. At a high ratio of 25:1, hollow nanospheres with an average diameter of ca. 100 nm were obtained.
In the presence of a large excess of thiourea, isotropic growth of CdS nanocrystallites occurred with their
domain sizes in [100] and [001] directions similar at ca. 20 nm. At the same time, the hollowing process was
promoted because of a fast mass transport. At lower molar ratios at 10:1 and 5:1, hollow interiors were not
observed and the diameters of the nanospheres increased to 200 and 280 nm. The nanocrystallites in these
larger nanospheres grew preferentially in [001] direction to ca. 40 nm. All the nanospheres formed have a
hexagonal wurtzite structure and exhibit good size uniformity and regularity. Furthermore, the as-prepared
hollow nanospheres demonstrated a good photocatalytic activity for methylene blue degradation by complete
oxidation under visible light.
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