In order to improve the initial coulombic efficiency (ICE) and cycle performance of SiO, in this study, the disproportionation reaction of commercial SiO is performed with the assistance of Na2CO3 under high temperatures. A polydopamine-based carbon is then in situ formed on the surface of the mixture (d-SiO-G) of disproportionated-SiO and graphite. It is found that an appropriate amount of Na2CO3 can effectively enhance the ICE of the commercial SiO due to the formation of Si, SiO2, and silicate; the mass ratio of d-SiO-G to the dopamine monomer is the important factor in influencing the cycling stability of the d-SiO-G@C composite. Due to the synergistic effect of graphite and the polydopamine-based carbon layer, the ICE for the d-SiO-G@C composite is 72.6%, and its capacity retention reaches 86.2% after 300 cycles, which is 11% higher than that of d-SiO-G. The modification method is an effective strategy for SiO materials in commercial applications.
To improve the air stability and cycling performance of P2-type Fe-based oxide, a thin active coating layer of K2Na(Co(NO2)6) was successfully synthesized by ion exchange reaction of Na3(Co(NO2)6) and KNO3 in aqueous solution. The ex-situ X-ray diffraction patterns and the micrograph of the modified cathode confirm that no phase change occurs during charging-discharging in the range of 1.5V- 4.2 V and reversible adsorption-desorption of H2O after charging to 4.2V. The cyclic voltammetry curves show that the increase of cyclic stability for modified material may be attributed to the reduce of Mn3+/Mn4+ polarization. The electrochemical impedance spectra also demonstrate that long-time stability of the active K2Na(Co(NO2)6) coating layer effectively suppress the increase of charge transfer impedance during cycles. Compared to Na0.67Fe0.5Mn0.35Co0.15O2 oxide, the modified material has superior capacity retention of 89.7% with a 30.1% improvement for 100 cycles at 1C (1C=180 mAh/g), and a discharge specific capacity of 94.6 mAh/g for 200 cycles.
Mo-Fe oxides catalysts were prepared by sol-gel and mechanical mixing methods.Physicochemical properties of the catalysts were investigated by means of XRD,IR and TG-DSC techniques.Effects of different preparation methods and Fe loadings on behaviors of the catalysts using gas-phase oxidation of p-xylene to terephthalic aldehyde(TPAL) as the probe reaction.The results showed that the catalyst prepared by sol-gel method exhibited optimal catalytic behaviors,with p-xylene conversion of 66.8% and selectivity to TPAL of 37.2% at Mo/Fe molar ratio of 3.TPAL yield of 24.8% was attained under the optimum condition.
A series of CuO-CeO 2 catalysts doped with transition metal oxides were prepared by co-precipitation method for selective CO oxidation and the effects of the additives on the catalytic performance were examined by H 2 -TPR, in-situ DRIFTS techniques. The results showed that the main CO adsorption site on CuO-CeO 2 series catalysts was Cu + species. The catalytic activity at lower temperatures was related to the CO desorption. The doping of ZnO improved the catalytic activity evidently and the CO conversion and selectivity of Cu 1 Zn 1 Ce 9 O 8 could reach 99.9% and 76.4% at 160°C, respectively. ZnO not only stabilized the reduced Cu + species, but also increased the capacity of CO adsorption.
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