P-N Heterojunction System Eu-Doped ZnO@GO for Photocatalytic Water Splitting.

Here, a feather-like Eu-doped ZnO (particle size ≈ 34.87 µm and E g ≈ 3.13 eV) nanoassembly is synthesized by using the capping agent cetyltrimethylammonium bromide-supported hydrothermal method. The Eu-doped ZnO is loaded onto the graphene oxide (GO) surface as Eu-doped ZnO@GO (particle size ≈ 23.07 µm and E g ≈ 0.79 eV) and applied to measure the photocatalytic water splitting activity in 20% CH3OH under a 300 W Xe light source. Eu-doped ZnO@GO exhibits the higher hydrogen generation activity of 255.8 µmol h-1 g-1 that is 159 and 1.5 times more than the pristine GO and Eu-doped ZnO systems, respectively. Eu-doped ZnO enhances the photocatalytic activity of GO because the p-n junction formed between GO and Eu-doped ZnO might support the charge-transfer and suppress charge recombination. The light harvesting power of Eu-doped ZnO@GO makes the charge transfer smooth through the GO network. Surface photovoltage and electrochemical impedance studies of the Eu-doped ZnO@GO composite, reveal that GO acts as the p-type semiconductor and Eu-doped ZnO works as an n-type semiconductor and their interface facilitates the p-n junction to ease charge separation and results in enhanced the water-splitting efficiency.

Electronic Structure and Room Temperature Ferromagnetism in Gd-doped Cerium Oxide Nanoparticles for Hydrogen Generation via Photocatalytic Water Splitting.

Enhanced visible light photocatalytic activity of Gd-doped CeO2 nanoparticles (NPs) is experimentally demonstrated, whereas there are very few reports on this mechanism with rare earth doping. All-pure and Gd-doped CeO2 NPs are synthesized using a coprecipitation method and characterized using X-ray diffraction (XRD), absorption spectroscopy, surface-enhanced Raman Spectroscopy (SERS), X-ray photoelectron spectroscopy (XPS), and superconducting quantum interference device (SQUID). The effect of Gd-doping on properties of CeO2 is discussed along with defects and oxygen vacancies generation. The XRD confirms the incorporation of Gd3+ at the Ce3+/Ce4+ site by keeping the crystal structure same. The average particle size from transmission electron microscopy (TEM) images is in the range of 5-7 nm. The XPS spectra of Ce 3d, O 1s, and Gd 4d exhibits the formation of oxygen vacancies to maintain the charge neutrality when Ce4+ changes to Ce3+. The gradual increase in hydrogen production is observed with increasing Gd concentration. The observed results are in good correlation with the characterization results and a mechanism of water splitting is proposed on the basis of analyses. The absorption spectra reveal optical band gap (2.5-2.7 eV) of samples, showing band gap narrowing leads to desired optical absorbance and photoactivity of NPs.

Photocatalytic CdSe QDs-decorated ZnO nanotubes: an effective photoelectrode for splitting water.

Arrays of ZnO nanorods (NRs) were successfully converted into nanotubes (NTs), used as photoelectrodes in photoelectrochemical (PEC) cells after their sensitization with CdSe quantum dots (QDs) and a strong correlation between the PEC performance and geometrical structure of ZnO NTs@CdSe(QDs) and ZnO NRs@CdSe(QDs) was established under the same conditions.