In-Situ Synthesis and High-Efficiency Photocatalytic Performance of Cu(I)/Cu(II) Inorganic Coordination Polymer Quantum Sheets.

Two-dimensional (2D) materials ultrathin quantum sheets have the advantage of elevating the catalysis performance and prominent edge effects, but most of them belong to element single valence materials. In this paper, the ultrathin Cu(I)/Cu(II) inorganic coordination polymer quantum sheet (ICPQS) {[CuII(H2O)4][CuI4(CN)6]} n is synthesized by controlling the appropriate molar ratio of raw material, reaction time, and temperature. Transmission electron microscopy (TEM) and atomic force microscope (AFM) analysis show that this ICPQS has a thickness of ∼0.2 nm. Due to the fact that about 58.16% of the Cu(I)/Cu(II) is occupied in molecular structure and most of the metal active sites are fully utilized, this ICPQS can accelerate the photocatalytic degradation of methylene blue (MB) (K = 2.5 mg·L-1·min-1 at pH 3) and organic compounds in coking wastewater and biotreated coking wastewater. Basing on mixed valences, the ICPQS can use visible light to promote energy transfer and increase quantum efficiency, paving the way for developing the next-generation monolayer 2D mixed valence photocatalysts.

Morphology-activity correlation of electrospun CeO2 for toluene catalytic combustion.

Herein, CeO2 catalysts with nanotube, nanobelt, and wire-in-nanotube morphologies were successfully fabricated by a facile single spinneret electrospinning technique. And catalytic activity of these electrospun CeO2 nanomaterials were evaluated by toluene catalytic combustion reaction. Among the three morphologies of CeO2 catalysts, CeO2 nanobelt (CeO2-NB) presented the best toluene catalytic combustion performance (T90% = 230 °C) at WHSV = 60,000 mL g-1 h-1, also exhibited the lowest activation energy (Ea = 80.2 kJ/mol). Based on the characterization by TEM, XRD, BET, SEM, XPS, Raman spectroscopy, H2-TPR, and O2-TPD results, the high catalytic activity of CeO2-NB catalyst was attributed to its porous nanobelt morphology with larger specific surface area and the abundance of surface oxygen vacancies. Furthermore, the CeO2-NB catalysts presented an excellent durability by longtime on-stream test (as well as presence of 5% vol. water vapor), suggesting its great potential for practical air pollution control application.

Leaf-like Co-ZIF-L derivatives embedded on Co2AlO4/Ni foam from hydrotalcites as monolithic catalysts for toluene abatement.

Herein, a series of distinctively monolithic catalysts were first synthesized by decorating leaf-like Co-ZIF-L derivatives on Co2AlO4 coral-like microspheres from CoAl layered double hydroxides (LDHs), which were coated on three-dimensional porous Ni foam. As a proof of concept application, toluene was chosen as a probe molecule to evaluate their catalytic performances over the as-synthesized catalysts. As a result, the L-12 sample derived from Co2AlO4@Co-Co LDHs displayed an excellent catalytic performance, cycling stability and long-term stability for toluene oxidation (T99 = 272 °C, 33 °C lower than that of Co2AlO4 sample), where leaf-like Co-ZIF-L served as a sacrificial template to synthesize Co-Co LDHs. The improved catalytic performance was attributed to its distinctive structure, in which leaf-like Co-ZIF-L derivatives on Co2AlO4 resulted in its higher specific surface area, lower-temperature reducibility, rich surface oxygen vacancy and high valence Co3+ species. This work thus demonstrates a feasible strategy for the design and fabrication of hybrid LDHs/ZIFs-derived composite architectures, which is expected to construct other novel monolithic catalysts with hierarchical structures for other potential applications.

Vertically-aligned Co3O4 arrays on Ni foam as monolithic structured catalysts for CO oxidation: effects of morphological transformation.

A generic hydrothermal synthesis route has been successfully designed and utilized to in situ grow highly ordered Co3O4 nanoarray (NA) precursors on Ni substrates, forming a series of Co3O4 nanoarray-based monolithic catalysts with subsequent calcination. The morphology evolution of Co3O4 nanostructures which depends upon the reaction time, with and without CTAB or NH4F is investigated in detail, which is used to further demonstrate the growth mechanism of Co3O4 nanoarrays with different morphologies. CO is chosen as a probe molecule to evaluate the catalytic performance over the synthesized Co-based oxide catalysts, and the effect of morphological transformation on the catalytic activity is further confirmed via using TEM, H2-TPR, XPS, Raman spectroscopy and in situ Raman spectroscopy. As a proof of concept application, core-shell Co3O4 NAs-8 presenting hierarchical nanosheets@nanoneedle arrays with a low density of nanoneedles exhibits the highest catalytic activity and long-term stability due to its low-temperature reducibility, the lattice distortion of the spinel structure and the abundance of surface-adsorbed oxygen (Oads). It is confirmed that CO oxidation on the surface of Co3O4 can proceed through the Langmuir-Hinshelwood mechanism via using in situ Raman spectroscopy. It is expected that the in situ synthesis of well-defined Co3O4 monolithic catalysts can be extended to the development of environmentally-friendly and highly active integral materials for practical industrial catalysis.