摘要: Three MoS2 catalysts were synthesized by a hydrothermal method using different sulfur precursors such as thiourea, L-cystine and sulfur powder; their differences in the structure, morphology, and catalytic activity in the hydrodeoxygenation (HDO) of p-cresol were comparatively investigated. The results illustrated that the sulfur source has a significant influence on the morphology and surface area of the as-synthesized MoS2 catalysts. All the hydrothermally synthesized MoS2 catalysts show much higher activity in HDO than the commercial MoS2 sample. Among three MoS2 catalysts, the one prepared from thiourea, with a high surface area and flower-like morphology, exhibits the highest activity in HDO; over it, a deoxygenation degree of 99.3% is achieved at 300℃.
摘要: MgCo2O4 composite oxides with spinel structure were hydrothermally prepared at 120℃ by using carbon sphere as template and urea as precipitant. K2CO3 solution was impregnated on MgCo2O4 and the K-modified catalyst was obtained. These catalysts were applied in catalytic decomposition of N2O and characterized by X-ray diffraction(XRD), nitrogen physisorption, scanning electron microscopy (SEM), temperature-programmed reduction of hydrogen (H2-TPR), temperature-programmed desorption of oxygen (O2-TPD), and X-ray photoelectron spectroscopy (XPS). Effect of catalysts preparation parameters such as mass ratio of cobalt and magnesium to carbon sphere, molar ratio of urea to metallic cations, on their catalytic activity was investigated. It is shown that the catalyst prepared with mass ratio 0.192 of cobalt and magnesium to carbon sphere, molar ratio 2 of urea to cobalt and magnesium cations, exhibits higher catalytic activity than others. Furthermore, 91% and 62% conversions of N2O could be reached over 0.02 K/MgCo2O4 catalyst at 400℃ after continuous running for 50 h under the atmosphere of oxygen-alone and oxygen-steam together, respectively, revealing that K-modified MgCo2O4 catalyst is stable under both reaction atmospheres.
摘要: Tungsten carbides microspheresare synthesized by in situ reduction of ammonium met tungstate microspheres (AMT) precursors as a function of reaction time under CO/CO2 mixture atmosphere. The morphology, size and composition of the as-prepared tungsten carbide microspheres are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Pt nanoparticles with a diameter of 4.6 nm are loaded onto the surface of WC microspheres using a conventional sodium borohydride reduction method. The electro-catalytic activity and stability toward methanol electrooxidation (MOR) are investigated using cyclic voltammetry (CV) and chronoamperometry(CA). The resultant Pt/WCO-6 h catalyst exhibits low onset potential and excellent catalytic performances in comparison to the commercial JM Pt/C and Pt/WC-15 h catalysts. Further investigation shows that besides the synergistic effect between WC and Pt, the existence of WO2 might also play an important role in improving the electro-catalytic activity, indicating the positive effect of the surface oxide on the activity and stability of Pt/WC catalysts towards MOR.
摘要: Direct methanol fuel cell (DMFC) research is highly focused due to its high energy density, portability and inexpensive. In the present study conventional platinum catalyst used for methanol oxidation is being replaced with nickel catalyst supported over nickel mesh. The electrode is synthesized by single step electro deposition technique. Synthesized electrode was characterized by SEM, EDAX and AFM techniques to know the surface morphology, composition and thickness of the catalyst respectively. The electro catalytic behavior of the nickel for methanol oxidation was evaluated using cyclic voltammetry technique. As the DMFC is compatible with both the acidic and alkaline electrolytes the working of the nickel mesh electrode is analyzed in both media. The results showed maximum current density of 0.025 and 0.030 A/cm2 in alkaline and acidic medium respectively with less potential around 0.4 and 0.2 V. The other parameters such as varying the concentration of methanol, electrolyte medium, scan rate and thickness of the catalytic layer were analyzed and optimized.
