Size Of Co3O4 Research Articles

Design of mesoporous heterojunction CuCo2O4/Co3O4 photocatalyst with superior photocatalytic degradation of tetracycline

The development of an active photocatalyst to destroy antibiotics under visible light is a significant challenge. In this contribution, novel mesoporous n-p heterojunction CuCo2O4/Co3O4 photocatalysts were constructed through a sol–gel process with varying CuCo2O4 percentages by impregnating CuCo2O4 on the mesoporous Co3O4 surface for the first time. TEM image demonstrated that the incorporation of CuCo2O4 on Co3O4 networks did not transform the form and size of Co3O4 (10–20 nm) with quite uniform. The synthesized CuCo2O4/Co3O4 photocatalysts were assessed for tetracycline (TC) degradation under visible illumination. The obtained CuCo2O4/Co3O4 heterostructures showed a remarkably larger photodegradation efficiency of TC than pure Co3O4. TC degradation efficiency of 100 % within 90 min was performed over 15 %CuCo2O4/Co3O4 heterostructure, which was 1.7 folds greater than that of Co3O4. The rate constant of 15 % CuCo2O4/Co3O4 heterostructure was 0.0488 min−1, which was 2.65 times larger than that of Co3O4. The superior photocatalytic ability of CuCo2O4/Co3O4 heterostructures was explained by the synergistic effect and the proper pore structure with large surface area, which not only promotes the absorption of visible light utilization but also accelerate the separation rate of photoinduced carriers. This research illustrates a novel insight into designing heterojunction based-photocatalysts Co3O4, presenting enhanced light absorption and photocatalytic ability.

Enhanced catalyst dispersion and structural control of Co3O4-silica nanocomposites by rapid thermal processing

We synthesized cobalt tetroxide (Co3O4) silica nanocomposites based on the conventional tetraethyl orthosilicate (TEOS) monomer and ethoxy polysiloxane (ES40) oligomer by sol-gel chemistry coupled with rapid thermal process (RTP). The physicochemical properties and structural formation of cobalt oxide silica nanocomposites were comprehensive characterized. By using ES40, well-controlled, homogeneous nanoparticle dispersion and size of Co3O4 with 5 nm within the silica matrix were achieved leading to fractal-like morphology. The concentration of the Co3O4 nanocatalyst was also significantly enhanced by more than 50 folds. Fenton-like HCO3−/H2O2 catalytic system using acid orange 7 and nanocomposites was examined for organic degradation. 98% AO7 and naphthalene intermediates degradation efficiency was achieved after 20 min with ES40-derived catalyst, which was three to ten folds faster than that of the TEOS-derived catalyst and the commercial Co3O4 catalyst. The combined use of ES40 sol-gel and RTP enabled a simple way to nanomaterial preparation and lowers overall processing time.

Catalytic activity of different sizes of Ptn/Co3O4 in the oxidative degradation of Methylene Blue with H2O2

In this work, we demonstrate the catalytic activity and kinetic analyses of generation six poly(amido-amine) hydroxyl-terminated (PAMAM), G6-OH(Ptn) (n = 55, 140, 225) dendrimer-encapsulated nanoparticles (DENs) immobilized onto mesoporous cobalt oxide (Co3O4) for the catalytic oxidation of methylene blue (MB). Ultra-Violet Visible (UV–Vis) spectrophotometry showed the ligand to metal charge transfer (LMCT) band of metal precursor ions coordinated to the tertiary amines of the dendrimer. The size of fully reduced Pt DENs and supported Pt nanoparticles were investigated using High-Resolution Transmission Electron Microscopy (HR-TEM). The mesoporous Co3O4 was synthesized by inverse micelle method, prior to Ptn DENs being supported on the Co3O4 via wet impregnation procedure. The crystallite structure and size of Co3O4 was investigated by powder X-ray diffraction (p-XRD) spectroscopy. Immobilized Ptn/Co3O4 structural analysis was investigated for the pore size and pore volume using N2 sorption techniques. Thermal gravimetric analyses (TGA) also indicated the dendrimer decomposition on the G6-OH(Ptn)/Co3O4 materials to be 550 °C. Hydrogen temperature programmed reduction (H2-TPR) analyses were conducted and the reducibility of the supported cobalt oxide showed only one temperature peak that was ascribed to the reduction of surface lattice oxygens. The experimental kinetic data was analyzed and fitted to the Langmuir-Hinshelwood model using elementary first-order reaction kinetics and the thermodynamic parameters were calculated. Catalyst Pt55/Co3O4 showed stability during the reusability investigation of up to 8 cycles. The G6-OH(Ptn) were immobilized on silica and tested for catalytic oxidation of MB as a control experiment.

Co/ZrO<sub>2</sub>-Al<sub>2</sub>O<sub>3</sub> Catalysts with Bimodal Pore Distribution for Fischer-Tropsch Synthesis

The Co/ZrO2-Al2O3 catalysts were prepared by impregnation method, and characterized via quantitative XRD, H2-TPR, and N2 adsorption-desorption techniques. The study showed that the addition of ZrO2 increased the interaction between active component and support, decreased the average crystallite size of Co3O4 and improved its dispersion. The performance tests presented that the Co/ZrO2-Al2O3 catalysts with bimodal pore distribution had high CO conversion and were more selective towards the gasoline fraction (C5-C10) and diesel fraction (C11-C18).

Influence of pore regularity on Fischer–Tropsch synthesis with Co/SiO2 Catalysts

Abstract The influence of pore regularity in Fischer–Tropsch synthesis over Co/SiO2 catalysts was investigated by using two series of silica with comparable pore sizes: mesoporous silica (SBA-15) and amorphous silica. It was found that cobalt dispersion was largely influenced by the support porous structure. The cobalt particles on mesoporous silica showed much more homogeneous size distribution and the increase of cobalt loadings did not result in a noticeable increase of Co3O4 particle size on SBA-15, while most of those on amorphous silica agglomerated into clusters. As a result, SBA-15 supported Co catalysts showed higher cobalt-time yield and C5+ selectivity in Fischer–Tropsch synthesis, particularly higher C12–18 fraction. However, the average particle size of Co3O4 supported on amorphous silica increased with the cobalt loadings, which led to lower cobalt-time yield and higher CH4 selectivity.

Nano-Sized Cobalt Based Fischer-Tropsch Catalysts for Gas-to-Liquid Process Applications

Nano-sized cobalt supported catalysts were prepared for Fischer-Tropsch synthesis in gas-to-liquid (GTL) process. The dependence of crystallite size and reducibility of Co3O4 on the supports were investigated with FTS activity. XRD peaks revealed nano crystallites (< 5.47 nm) of Co3O4 crystallites. TEM showed round shaped particles with size less than 5 nm. Support with higher acidity decreased crystallite size of Co3O4. XRD data of used catalysts showed Co3O4 crystallites smaller than 3.5 nm which do not reduce easily to Co(0) state. The crystallite size of Co3O4 plays a role in its reduction to Co(0). TPR results showed that the reduction temperature shifts to higher temperature due to metal-support interaction. The variation in the activity of the catalysts depends on the support which in turn affects the crystallite size, dispersion, reducibility and activity of Co species in Fischer-Tropsch Synthesis (FTS). In this study, Co/Al2O3 showed higher CO conversion than the other catalysts. However, the C5+ production was in order Co/SiO2 (78.1%) > Co/Al2O3 (70.0%) > Co/R_TiO2 (61%) > Co/A_TiO2 (57.5%).