ABSTRACT
Alkaline-earth metal Ca2+ modified CdS nanocrystals have been designed for the first time for highly efficient H2 evolution from hydrogen sulfide (H2S) with Na2SO3 as a favourable reaction medium. The advantage of Na2SO3 was revealed by an electrochemical test, and the conversion of Na2SO3 during the reaction was carefully studied. Particularly, most of Na2SO3 was converted into Na2S2O3. Highly value-added utilization of waste H2S is therefore achieved via photocatalysis.
ABSTRACT
Through direct addition of inorganic zinc ions into the solution of indium phosphide quantum dots (InP QDs) at ambient environment, we here present a facile but effective method to modify InP QDs for photocatalytic hydrogen evolution from hydrogen sulfide (H2S). X-ray diffraction patterns and transmission electron microscopic images demonstrate that zinc ions have no significant influence on the crystal structure and morphology of InP QDs, while X-ray photoemission spectra and UV-Vis diffuse and reflectance spectra indicate that zinc ions mainly adsorbed on the surface of InP QDs. Photocatalytic results show the average hydrogen evolution rate has been enhanced to 2.9 times after modification and H2S has indeed involves in the hydrogen evolution process. Steady-state and transient photoluminescence spectra prove that zinc ions could effectively eliminate the surface traps on InP QDs, which is crucial to suppress the recombination of charge carriers. In addition, the electrostatic interaction between zinc ions and the surface sulfide from InP QDs could mitigate the repulsion between QDs and sulfide/hydrosulfide, which may promote the surface oxidative reaction during photocatalysis. This work avoids the traditional harsh and complicated operations required for surface passivation of QDs, which offers a convenient way for optimization of QDs in photocatalysis.
ABSTRACT
Novel photocatalysts -CdSe quantum dots (QDs)/g-C3N4- were successfully constructed. The structure, chemical composition, and optical properties of the prepared samples were investigated via a series of characterization techniques. The results indicated that CdSe QDs/g-C3N4 photocatalysts exhibited remarkably enhanced photocatalytic activity for visible-light-induced H2 evolution compared to pristine g-C3N4 and CdSe QDs and addition of 13.6 wt % CdSe QDs into the composite photocatalyst generated the highest H2 production rate. The enhanced photocatalytic performance of CdSe QDs/g-C3N4 can be attributed to the synergistic effects of excellent visible absorption and high charge separation efficiency from the heterostructure. This work could not only provide a facile method to fabricate semiconductor QDs-modified g-C3N4 photocatalysts but also contribute to the design for heterostructures.
