One-pot microwave-hydrothermally synthesized carbon nanotube-cerium oxide nanocomposites for enhanced visible photodegradation of acid orange 7.

Carbon nanotubes (CNT)-cerium oxide (CeO2) nanocomposites were fabricated successfully by one-pot microwave hydrothermal growth of regular CeO2 nanoparticles with a size of 8 nm on hydroxyl-functionalized multi-walled CNTs. These nanocomposite photocatalysts demonstrated an acid orange (AO7) photocatalytic degradation efficiency of above 90% under solar-simulated light irradiation for 3 h, which was much higher than that of the pure CeO2 nanoparticles. The enhanced photocatalytic activity was observed to mainly originate from the ˙O2- and hole traps, while the hydroxyl radical ˙OH played a secondary role.

3D Porous Amorphous γ-CrOOH on Ni Foam as Bifunctional Electrocatalyst for Overall Water Splitting.

The development of novel and highly efficient bifunctional electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is an ongoing challenge. The Cr3+ cation has a special electronic configuration (t32ge0g), which facilitates charge transfer and electron capture. However, Cr-based materials applied on water-splitting electrocatalysis is still a research void up to now. Herein, a novel amorphous γ-CrOOH was developed as a bifunctional electrocatalyst toward overall water splitting for the first time. It shows extraordinary HER activity with an ultralow overpotential of only 149 mV at 50 mA cm-2. Meantime, there is a small overpotential of 334 mV at 50 mA cm-2 for the OER. Importantly, the bifunctional electrocatalyst for overall water-splitting electrocatalysis can work with a cell voltage of merely 1.56 V at 10 mA cm-2. Amorphous γ-CrOOH has effectively enhanced the intrinsic electrochemical activity via density functional theoretical calculations. Therefore, this work not only provides a new method for preparation of amorphous γ-CrOOH but also expands the types of catalysts for water splitting.

N self-doped ZnO derived from microwave hydrothermal synthesized zeolitic imidazolate framework-8 toward enhanced photocatalytic degradation of methylene blue.

The precursor particles were successfully prepared by a facile microwave hydrothermal method. Compared with solvothermal and precipitation method, microwave hydrothermal method can greatly shorten the reaction time and increase the product yields. Nitrogen (N) doped zinc oxide (ZnO) nanoparticles were derived via one-step controllable pyrolysis of zeolitic imidazolate framework-8 (Zif-8) precursors under 550 °C. The powder X-ray diffraction (XRD) analysis, elemental mapping image, energy dispersive spectrometry (EDS) spectra and X-ray photoelectron spectroscopy (XPS) analysis proved that Zif-8 particles were converted to ZnO and the N atoms were successfully doped into ZnO lattice. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results demonstrated that N doped ZnO retained the morphology of Zif-8 with a particle size of approximately ~70 nm and the UV-visible diffuse reflectance spectra (UV-vis DRS) showed that the as-prepared N doped ZnO possessed a lower band gap (3.16 eV) than commercial ZnO (3.26 eV). The photocatalytic activities of the as-prepared samples were evaluated by the degradation rate of methylene blue (MB) upon irradiation with solar-simulated light. The photocatalytic degradation efficiency of N doped ZnO was 95.3% after 80 min illumination, which was much higher than that of other samples prepared by other methods. Quenching tests proved that the photo-generated holes (h+) played a main role in the photodegradation of MB under solar-simulated light irradiation.

Engineering borate modified NiFe layer double hydroxide nanoarrays as "hydroxyl ions hungry" electrocatalysts for enhanced oxygen evolution.

NiFe layered double hydroxides (NiFe-LDHs) have been regarded as significant electrocatalysts for the oxygen evolution reaction (OER). However, their overpotential must still be further reduced to enable commercial applications. Herein, a promising and highly effective "hydroxyl ions hungry" electrode structure was prepared for the first time via a two-step hydrothermal reaction procedure to enhance the surface adsorption kinetics to obtain an ultralow overpotential. The electrode exhibits OER activity with ultralow overpotentials of 203 mV and 293 mV at the current densities of 10 mA cm-2 and 100 mA cm-2, respectively, in 1.0 M KOH. These results reveal an important way to improve the catalytic performance in an alkaline medium.