Browsing by browse.metadata.impactarea "24 Energy Materials"

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    Electrochemical deposition of PdBiSn catalyst for glycerol oxidation in alkaline medium
    (2020-12) Xaba, Nqobile; Modibedi, Remegia M; Mathe, Mahlanyane K; Khotseng, LE
    PdBiSn thin film on Au substrate was prepared by means of the electrochemical atomic layer deposition (E-ALD) technique. The morphology and elemental distribution of the catalysts was determined using scanning electron microscope equipped with energy dispersive spectroscopy (EDS) detector. The catalysts contained all the deposited elements distributed evenly on the surface. Electro-oxidation of glycerol was tested in alkaline media using cyclic voltammetry (CV) and chronoamperometry (CA). The activity of the catalysts towards the oxidation of glycerol improved with the addition of Sn and Bi with the binary PdBi catalyst being the most improved.
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    The ultrasonication boosts the surface properties of CoFe2O4/C nanoparticles towards ORR in alkaline media
    (2020-06) Matseke, Mphoma S; Zheng, Haitao; Wang, Y
    Since ultrasonication was reported to be used for exfoliation of layered materials in water (Science-ref. 31), the method has never been explored in non-layered materials, in particular, the effect of ultrasonication on the surface property of materials. In this work, CoFe2O4/C nanoparticles were synthesized and processed using ultrasonic treatment in water. Through the ultrasonic treatment, the electrocatalytic activity of the CoFe2O4/C nanoparticles towards ORR was improved significantly with a higher mass activity (5.05 mA mg−1) than the original CoFe2O4/C (2.75 mA mg−1) in O2-saturated 0.1 M KOH solution. The half-wave potential on the original CoFe2O4/C was also shifted to the positive side by 60 mV. Furthermore, the treated CoFe2O4/C catalyst exhibits a constant half-wave potential with better onset potential after 2000 cycles, and a 50 mV of half-wave potential on the original catalyst was moved to negative under same test condition. The analysis from characterizations reveals that the enhanced ORR performance of the treated CoFe2O4/C resulted from the Co2+ and Fe3+ enriched surface with more cations being occupied in the tetrahedral sites than the octahedral sites after ultrasonic treatment. In addition, compared to the original CoFe2O4/C catalyst, the specific surface area of the treated CoFe2O4/C was improved 1.8 times, mesoporous grown to microspores with 2.2 times increased volumes, which has provided higher active sites and accelerated transport between O2 and electrolyte during the ORR process. The ORR via the 4-electron transfer pathway on the treated CoFe2O4/C catalyst, while the 2-electron transfer process is favoured on the original CoFe2O4/C catalyst. This further signifies that the ultrasonic process had significantly influence on the electrochemical properties of the CoFe2O4/C catalyst.