152 research outputs found
Electrode surface modification using metallophthalocyanines and metal nanoparticles : electrocatalytic activity
No full textMetallophthalocyanines and metal nanoparticles were successfully synthesized and applied for the electrooxidation of amitrole, nitrite and hydrazine individually or when employed together. The synthesized materials were characterized using the following techniques: predominantly scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), electrochemistry and scanning electrochemical microscopy (SECM). Different electrode modification methods were used to modify the glassy carbon substrates. The methods include adsorption, electrodeposition, electropolymerization and click chemistry. Modifying the glassy carbon substrate with MPc (electropolymerization) followed by metal nanoparticles (electrodeposition) or vice versa, made a hybrid modified surface that had efficient electron transfer. This was confirmed by electrochemical impedance studies with voltammetry measurements having lower detection potentials for the analytes. This work also describes for the first time the micropatterning of the glassy carbon substrate using the SECM tip. The substrate was electrografted with 4-azidobenzenediazonium salt and then the click reaction was performed using ethynylferrocene facilitated by Cu⁺ produced at the SECM tip. The SECM imaging was then used to show the clicked spot
The effect of addition of ceria on platinum supported on carbon materials in the hydrogenation of ethylene
No full textThis study reports the synthesis of carbon materials (carbon nanotubes (CNTs), coiled carbon
nanofibers (CCNFs) and carbon spheres (CSs)) using the chemical vapour deposition (CVD)
method. The as-synthesized carbon materials were functionalized using nitric acid in order to
introduce functional groups and improve the hydrophilic behavior of the carbon materials. Both
the as-synthesized and functionalized carbon materials were characterized by TEM, TGA,
Raman and FTIR spectroscopy. The presence of functional groups was confirmed by alkalimetry
titration and IR spectroscopy data. Ceria (synthesized using the sol-gel method), activated carbon
(AC) and titania (P25) were other catalysts supports used and their morphologies were
determined by TEM.
Platinum was deposited on the various supports to give Pt loadings of 0.5, 1 and 5 % using the
polyol method. It was found that small Pt particle sizes were obtained with average particle sizes
of 1.8, 2.3, 2.6, 2.9, 2.7 and 1.6 nm for Pt/CCNF, Pt/CNT, Pt/CS, Pt/AC, Pt/CeO2 and Pt/TiO2
respectively at 0.5 % Pt loading. Pt was also deposited on the CeO2/CM supports (5 % and 10 %
CeO2 loadings) to make Pt-CeO2/CM catalysts. The Pt supported catalysts were characterized by
TEM, EDS, XRD, TPR, BET and TGA.
The platinum supported catalysts were tested for the hydrogenation of ethylene. The effect of
functionalization of the carbon materials was determined. Pt/functionalized carbon materials had
better activity than Pt/as-synthesized carbon materials. On the effects of supports; Pt/TiO2
showed the best activity compared to Pt/CCNF, Pt/CNT, Pt/CS, Pt/AC, Pt/CeO2 and this was
attributed to the small Pt sizes formed on TiO2 (Pt mean size was 1.6 nm). An interesting feature
in this study was the higher activity of the Pt-CeO2/CM as compared to Pt/CM. This was due to
the effect of ceria in preserving the surface area of Pt by suppressing sintering. The effect of
increasing the ratio of hydrogen to ethylene was investigated and the findings indicated that all
the ethylene was converted to ethane. This was attributed to the fact that at a high hydrogen
concentration, the rate of formation of the carbon deposit is slow and the rate of hydrogenation is
high. No carbon deposits are thus expected on the Pt catalyst particles. It was found that an
increase in the Pt loading resulted in an increase in the rate of reaction
Behavior of Palladium Nanoparticles in the Absence or Presence of Cobalt Tetraaminophthalocyanine for the Electrooxidation of Hydrazine
No full textWe report on the electrodeposition of palladium nanoparticles (PdNPs) on a glassy carbon electrode (GCE) and onto a poly-CoTAPc-GCE (CoTAPc=cobalt tetraamino phthalocyanine) surface. The electrodes are denoted as PdNPs-GCE and PdNPs/poly-CoTAPc-GCE, respectively. PdNPs/poly-CoTAPc-GCE showed the best activity for the oxidation of hydrazine at the lowest potential of −0.28 V and with the highest currents. The results were further supported by electrochemical impedance spectroscopy (EIS) which showed that there was less resistance to charge transfer for PdNPs/poly-CoTAPc-GCE compared to PdNPs-GCE. The catalytic rate constant for hydrazine oxidation was 6.12×108 cm3 mol−1 s−1 using PdNPs/poly-CoTAPc-GCE.Original publication is available at http://dx.doi.org/10.1002/elan.20140002
The influence of gold nanoparticles on the electroactivity of nickel tetrasulfonated phthalocyanine
No full textWe report on the electrodeposition of gold nanoparticles (AuNPs) on a glassy carbon electrode (GCE) followed by deposition of nickel tetrasulfonated phthalocyanine (NiTSPc) film by electropolymerization (poly-NiTSPc-GCE) to form Poly-NiTSPc/AuNPs-GCE. The presence of the gold nanoparticles caused a lowering of the anodic and cathodic peak separation (ΔEp) of ferricyanide from 126 mV on poly-NiTSPc to 110 mV on poly-NiTSPc/AuNPs. The electrooxidation of nitrite improved on modified electrodes compared to GCE, with the latter giving Ep = 0.78 V and the modified electrodes gave Ep = 0.62 V or 0.61 V. Poly-NiTSPc/AuNPs-GCE had higher currents compared to poly-NiTSPc-GCE. This indicates the enhancement effect caused by the AuNPs. Electrochemical impedance spectroscopy and chronoamperometric studies also showed that poly-NiTSPc/AuNPs-GCE was a better electrocatalyst than poly-NiTSPc-GCE or AuNPs-GCE
The Audacity to Live: Critical Introduction
No full textThis is a critical introduction from a thesis project: a creative nonfiction collection of personal essays titled The Audacity to Live. The critical introduction is an interrogation of the student’s work with a focus on creative influences, craft influences, and market considerations. The author was an English graduate student, and their faculty mentor was Professor Rob Davidson. This paper utilized the Modern Language Association (MLA) Style, which is typical for papers in this discipline and used in-text citations
Kant: the audacity of judgement
No full textIn the legal judgement reason demands that it extend itself beyond the mere subjective limits of the self in order that it might fashion a judgement that speaks for the other. This is the universal necessity of the judgement. No claim of truth or the moral law can guarantee that others will agree with this judgement: thus disputation is the risk which reason takes in order to judge at all. The author examines this audacity of judgement by reference to Kant’s autonomy of reason, which risks itself in the thought that thinks
Electrochemical behaviour of gold nanoparticles and Co tetraaminophthalocyanine on glassy carbon electrode
No full textWe report on the electrodeposition of gold nanoparticles (AuNPs) onto the glassy carbon electrode (GCE) followed by polymerization of cobalt tetraamino phthalocyanine (CoPc(NH2)4) on top (represented as poly-CoPc(NH2)4-/AuNPs-GCE). The modified electrode where CoPc(NH2)4 is polymerized first followed by deposition of AuNPs is represented as AuNPs/poly-CoPc(NH2)4-GCE. In the absence of AuNPs, the electrode is represented as poly-CoPc(NH2)4-GCE or for AuNPs alone (AuNPs-GCE). The surface coverage was 1.5 × 10−9 mol cm−2 for AuNPs-GCE and 3.0 × 10−9 mol cm−2 for the rest of the modified electrodes. AuNPs/CoPc(NH2)4-GCE exhibited high electrocatalytic activity towards the oxidation of nitrite, with detection potential of 0.76 V. The catalytic rate constant of 3.96 × 107 cm3 mol−1 s−1 was obtained for nitrite oxidation.Original publication is available at http://dx.doi.org/10.1016/j.electacta.2013.12.13
Characterization of electrodes modified by one pot or step by step electro-click reaction and axial ligation of iron tetracarboxyphthalocyanine
No full textThe modification of the glassy carbon electrode (GCE) was carried out using two methods. The first method is simultaneous electropolymerization and electro-click followed by immersion into a solution of dimethyl formamide (DMF) containing FeTCPc. The second method is step by step whereby electropolymerization is carried out first followed by electro-click and then immersion into a DMF solution containing FeTCPc. From the electrochemical characterization, it was observed that the second route (step by step method) was the best as indicated by the ferricyanide studies (cyclic voltammetry and scanning electrochemical microscopy). In the electrooxidation of hydrazine, we obtained a potential of 0.26 V. Of interest were the detection limit of 6.4 μM and the catalytic rate constant of 2.1 × 109 cm3 mol−1 s−1. This shows that the sensor can be used for the electrooxidation of hydrazine.Original publication is available at http://dx.doi.org/10.1016/j.electacta.2014.09.01
Electrocatalytic activity of bimetallic Au–Pd nanoparticles in the presence of cobalt tetraaminophthalocyanine
No full textAu and Pd nanoparticles were individually or together electrodeposited on top of polymerized cobalt tetraaminophthalocyanine (poly-CoTAPc). When Pd and Au nanoparticles are co-deposited together, the electrode is denoted as Au–Pd (co-deposited)/poly-CoTAPc-GCE. X-ray photoelectron spectroscopy (XPS) was used to show the successful deposition of AuNPs, PdNPs and Au–Pd (co-deposited). The scanning electrochemical microscopy showed that Au–Pd (co-deposited)/poly-CoTAPc-GCE (with current range of 9.5–13.5 μA) was more conducting than Au–Pd (co-deposited)-GCE (with current range of 8–12 μA). Electrochemical impedance spectroscopy (EIS) showed that there was less resistance to charge transfer for Au–Pd (co-deposited)/poly-CoTAPc-GCE compared to the rest of the electrodes. Au–Pd (co-deposited)/poly-CoTAPc-GCE showed the best activity for the electrooxidation of hydrazine in terms of limit of detection (0.5 μM), hence shows promise as an electrocatalyst for electrooxidation of hydrazine.Original publication is available at http://dx.doi.org/10.1016/j.jcis.2014.10.05
Electrocatalytic activity of bimetallic Au–Pd nanoparticles in the presence of cobalt tetraaminophthalocyanine
No full textAu and Pd nanoparticles were individually or together electrodeposited on top of polymerized cobalt tetraaminophthalocyanine (poly-CoTAPc). When Pd and Au nanoparticles are co-deposited together, the electrode is denoted as Au–Pd (co-deposited)/poly-CoTAPc-GCE. X-ray photoelectron spectroscopy (XPS) was used to show the successful deposition of AuNPs, PdNPs and Au–Pd (co-deposited). The scanning electrochemical microscopy showed that Au–Pd (co-deposited)/poly-CoTAPc-GCE (with current range of 9.5–13.5 μA) was more conducting than Au–Pd (co-deposited)-GCE (with current range of 8–12 μA). Electrochemical impedance spectroscopy (EIS) showed that there was less resistance to charge transfer for Au–Pd (co-deposited)/poly-CoTAPc-GCE compared to the rest of the electrodes. Au–Pd (co-deposited)/poly-CoTAPc-GCE showed the best activity for the electrooxidation of hydrazine in terms of limit of detection (0.5 μM), hence shows promise as an electrocatalyst for electrooxidation of hydrazine.Original publication is available at http://dx.doi.org/10.1016/j.jcis.2014.10.05
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