ABSTRACT
The pseudocapacitive properties of CeO2 are largely dependent on its surface Faradaic redox reaction kinetics; however, its electrochemical performance is still limited by the low utilization due to the inefficient diffusionfreeways and the limited active sites. Herein, we prepare a 0D/3D composite composed of oxygen-deficient CeO2 quantum dots (0D) anchored on a 3D hollow porous N-doped carbon framework (CeO2-x QD@PHC) via a facile template-confined strategy followed by a chemical co-precipitation. The refined QDs and hollow structure greatly shorten the ion diffusion paths and lower the internal strain during cycling. The integration of CeO2-x QDs with PHC structure endows enriched accessible active sites and enhances the electrical properties. As a result, the optimized CeO2-x QD@PHC exhibits an improved specific capacitance and good rate performance in comparison to those of the CeO2-x-free PHC. Moreover, a symmetric supercapacitor with CeO2-x QD@PHC as an electrode is constructed, delivering a high energy density of 3.874 Wh kg-1 at a power density of 149.98 W kg-1.
ABSTRACT
Heavy metals are one of the most common types of pollutants in ground water due to their wide sources, non-degradability and high toxicity. Many traditional wastewater treatments were not capable of removing enough such contaminants in order to meet quality standards. Nanosized zerovalent transition metals have emerged as a great candidate for ground water remediation, due to their simplicity and low fabrication cost, furthermore they can comply with simple chemical synthesis. Here, we present the synthesis of nano zerovalent nickel (nZVN) by a simple grinding reduction method. The obtained nZVN was characterized with XRD, SEM, EDS and BET surface area. The results confirms the formation of nZVN and the active particle cluster size ranges from 100 to 200 nm. N2 adsorption isotherms revealed that the formation mesoporous cluster of nZVN with good surface area. The adsorption of Cr(VI) using nZVN showed 96% removal efficiency for 10 ppm concentration, and even up to 98% when the temperature is slightly raised to 36 °C (309 K). The removal efficiencies of Cr by zerovalent nickel was well fitted by the Langmuir-Hinshelwood first order reaction kinetic model with deceptive rate constant values of 0.6699, 0.7956 and 1.0251 min-1 at temperature 200, 303 and 309 K, respectively. In total, our studies suggest that nanoscale zerovalent iron is a capable material for Cr(VI) remediation from groundwater.
ABSTRACT
Biodiesel synthesis was carried out via heterogeneous catalysis of canola oil with nanoparticles of a mixed oxide based on rare earths. The catalyst synthesis (NdAlO3) was carried out based on the method proposed by Pechini for the synthesis of nanoparticles. Thermogravimetric analysis-differential thermal analysis (TGA-DTA) analysis was performed on the nanoparticle precursor gel in order to establish the optimum conditions for its calcination, with these being of 800 °C over 24 h. A pure NdAlO3 compound with an approximate size of 100 nm was obtained. The products of the transesterification reaction were analyzed using gas chromatography, FTIR, and NMR. The optimum reaction conditions were determined, namely, the temperature effect, reaction time, methanol:oil mass ratio, and recyclability of the catalyst. These studies showed the following optimal conditions: 200 °C, 5 h, methanol:oil mass ratio of 6:1, and a constant decrease in the catalytic activity of the catalyst was observed for up to six reuses, which later remained constant at around a 50% conversion rate. The maximum biodiesel yield obtained with the optimum conditions was around 75%. Analysis of the reaction products showed that the residual oil showed a chemical composition different from that of the source oil, and that both the biodiesel and glycerol obtained were of high purity.
