Electrocatalytic Activity Of Carbon Nanotubes Research Articles

Front Cover: The Effect of Functional Groups on the Electrocatalytic Activity of Carbon Nanotubes with Different Wall Numbers toward Carbohydrazide Oxidation Reaction (Chem. Asian J. 21/2020)

Front Cover: The Effect of Functional Groups on the Electrocatalytic Activity of Carbon Nanotubes with Different Wall Numbers toward Carbohydrazide Oxidation Reaction (Chem. Asian J. 21/2020)

The Effect of Functional Groups on the Electrocatalytic Activity of Carbon Nanotubes with Different Wall Numbers toward Carbohydrazide Oxidation Reaction.

Carbohydrazide could be applied as fuels for fuel cells to avoid the toxicity of hydrazine. Carbon nanotubes (CNTs) exhibit an improved electrocatalytic activity toward carbohydrazide oxidation reaction than other carbon materials like carbon black or multi-layer graphene, however, the role of defects and functional groups of CNTs for the reaction is not clear. In this study, the electrocatalytic properties of CNTs toward the carbohydrazide oxidation reaction is investigated, which demonstrate that the content of carboxyl groups is crucial to the catalytic activity. The one with higher carboxyl groups exhibits an improved catalytic activity toward carbohydrazide oxidation reaction. Furthermore, density functional theory calculation reveals that the carboxyl groups could increase the adsorption of carbohydrazide molecules on CNTs, which benefits their catalytic activity.

Effect of the pH of the preparation medium on the microstructure and electrocatalytic activity of carbon nanotubes decorated with PtSn nanoparticles for use in methanol oxidation

Effect of the pH of the preparation medium on the microstructure and electrocatalytic activity of carbon nanotubes decorated with PtSn nanoparticles for use in methanol oxidation

Effect of the pH of the preparation medium on the microstructure and electrocatalytic activity of carbon nanotubes decorated with PtSn nanoparticles for use in methanol oxidation

Carbon nanotubes (CNTs) decorated with PtSn nanoparticles (PtSn/CNT) were prepared by the microwave-assisted ethylene glycol reduction method and characterized by atomic adsorption spectroscopy, X-ray diffraction and transmission electron microscopy. Results indicated that the loading efficiency of the metal catalyst, and the degree of alloying and morphology of the PtSn nanoparticles were significantly affected by the solution pH value of the metallic ions in the ethylene glycol. The required composition of the PtSn/CNT catalysts could be obtained by adjusting the pH value to about 5, which is almost the isoelectric point of the acid-treated CNTs. The size of the PtSn nanoparticles decreased with the pH value in the range 2 to 7, but they became large and agglomerated when the pH value was greater than 7. Electrocatalytic activity tests indicated that the PtSn/CNTs prepared at pH 5 had the best catalytic performance towards methanol oxidation. The improvement in catalytic activity was mainly attributed to a high loading efficiency and control of particle shape and size distribution.

Effects of pH on Electrocatalytic Activity of Carbon Nanotubes in Poly(acrylic acid) Composites Used for Electrochemical Selective Detection of Uric Acid and Dopamine in the Presence of Ascorbic Acid

Effects of pH on Electrocatalytic Activity of Carbon Nanotubes in Poly(acrylic acid) Composites Used for Electrochemical Selective Detection of Uric Acid and Dopamine in the Presence of Ascorbic Acid

Effects of pH on electrocatalytic activity of carbon nanotubes in polyethylenimine composites

In this study, we first investigated dispersion of the COOH functionalized carbon nanotubes (fCNT) in polyethylenimine (PEI) aqueous solution of pH 1–13 by solubility observation, zeta potential, and transmission electron microscopy. The fCNT/PEI dispersions of different pH were then cast on ITO electrode to investigate electrochemical behavior of the composites by cyclic voltammetry (CV) and electrochemical impedance spectroscopy. Solubility data found that the fCNT well dispersed in PEI aqueous solutions of pH 1–11 except 13 but precipitated in pure aqueous solutions of pH 1, 3, and 13. The fCNT dispersion improved by PEI in low pH solutions could be attributed to the interactions of the NH 3 + of PEI and the COO − of fCNT. At a pH in the range of 3 to 11 at which ITO electrode was modified by the cast composite, the dispersed fCNT was found to electrocatalyze the redox reactions of the Fe ( CN ) 6 3 - / 4 - probe and the PEI matrix could enhance the catalytic ability of fCNT leading to strong redox current intensity in CV curves. The fCNT/PEI composites cast from solutions at pH 1 and 13 exhibited no redox signals of the Fe ( CN ) 6 3 - / 4 - probe. The pH variational fCNT dispersions in the fCNT/PEI composites and the interactions of Fe ( CN ) 6 3 - / 4 - and NH 3 + of PEI could be used to justify the CV curves. The fCNT/PEI composite cast from aqueous solution of pH 11 exhibited the least oxidation potential, the most reversible redox reactions, and the largest oxidation current intensity of the Fe ( CN ) 6 3 - / 4 - probe.

Effects of pH on electrocatalytic activity of functionalized carbon nanotubes

In this study, we modified carbon nanotubes (CNTs) by grafting with poly(ethylene glycol) (PEG) using the “grafting to” method. The PEG-grafted CNT (CNT-g-PEG) was cast on indium tin oxide (ITO) electrode to investigate the electrocatalytic activity of CNT to the redox reactions of the Fe(CN) 6 3−/4− as a probe using cyclic voltammetry and electrochemical impedance spectroscopy. The electrocatalytic activity of CNT was correlated with CNT dispersion in the cast film on ITO as a function of pH of aqueous solution from which the film was cast. The CNT dispersions in aqueous solutions of different pH and in the cast films were examined by visual observation and zeta potential, scanning electron microscopy and transmission electron microscopy, respectively. At a pH in the range of 3–11 at which ITO electrode was modified, two functionalized CNT (fCNT and CNT-g-PEG) were both found to electrocatalyze the redox reactions of the Fe(CN) 6 3−/4− probe and the PEG grafts in CNT-g-PEG could help CNT adhere to the electrode to obtain durable modified electrode. The more uniform CNT dispersions in aqueous solutions and in the cast films appeared to have greater electrocatalytic acitivity.

Novel phosphorus-doped multiwalled nanotubes with high electrocatalytic activity for O2 reduction in alkaline medium

Abstract Phosphorus-doped multiwalled carbon nanotubes (MCNTs) were synthesized by the thermolysis and characterized by electron microscopy and microanalysis technique and evaluated with electrochemical methods. The results revealed that carbon nanotube length became shorter, the tube diameters increased and the yield of MCNTs reduced gradually with the increase of the concentration of triphenylphosphine in toluene solution, and the tube diameters increased with the increase of the synthesis temperature. Moreover, the phosphorus doping significantly improved the electrocatalytic activity of carbon nanotubes for the oxygen-reduction reaction in alkaline media, and the carbon nanotubes doped with small amounts of phosphorus exhibited higher electrocatalytic activity and stability than Pt/C catalyst.

Nanographitic impurities are responsible for electrocatalytic activity of carbon nanotubes towards oxidation of carbamazepine

Carbamazepine is one of the most extensively prescribed drug and its residues can be found in the ground and surface waters. Recently, a new method for the sensitive “electrocatalytic” determination of carbamazepine on carbon nanotube electrodes was developed. We demonstrate here that the reported excellent electrocatalytic properties of carbon nanotubes for the oxidation of carbamazepine are caused by the presence of nanographitic impurities within the carbon nanotubes.

Amperometric Glucose Biosensor Based on Glucose Oxidase Encapsulated in Carbon Nanotube–Titania–Nafion Composite Film on Platinized Glassy Carbon Electrode

AbstractA highly sensitive and selective glucose biosensor has been developed based on immobilization of glucose oxidase within mesoporous carbon nanotube–titania–Nafion composite film coated on a platinized glassy carbon electrode. Synergistic electrocatalytic activity of carbon nanotubes and electrodeposited platinum nanoparticles on electrode surface resulted in an efficient reduction of hydrogen peroxide, allowing the sensitive and selective quantitation of glucose by the direct reduction of enzymatically‐liberated hydrogen peroxide at −0.1 V versus Ag/AgCl (3 M NaCl) without a mediator. The present biosensor responded linearly to glucose in the wide concentration range from 5.0×10−5 to 5.0×10−3 M with a good sensitivity of 154 mA M−1cm−2. Due to the mesoporous nature of CNT–titania–Nafion composite film, the present biosensor exhibited very fast response time within 2 s. In addition, the present biosensor did not show any interference from large excess of ascorbic acid and uric acid.

V-Type Nerve Agent Detection Using a Carbon Nanotube-Based Amperometric Enzyme Electrode

An enzyme electrode for the detection of V-type nerve agents, VX (O-ethyl-S-2-diisopropylaminoethyl methylphosphonothioate) and R-VX (O-isobutyl-S-2-diethylaminoethyl methylphosphonothioate), is proposed. The principle of the new biosensor is based on the enzyme-catalyzed hydrolysis of the nerve agents and amperometric detection of the thiol-containing hydrolysis products at carbon nanotube-modified screen-printed electrodes. Demeton-S was used as a nerve agent mimic. 2-(Diethylamino)ethanethiol (DEAET) and 2-(dimethylamino)ethanethiol (DMAET), the thiol-containing hydrolysis product and hydrolysis product mimic of R-VX and VX, respectively, were monitored by exploiting the electrocatalytic activity of carbon nanotubes (CNT). As low as 2 microM DMAET and 0.8 microM DEAET were detected selectively at a low applied potential of 0.5 V vs Ag/AgCl at a CNT-modified mediator-free amperometric electrode. Further, the large surface area and the hydrophobicity of CNT was used to immobilize organophosphorus hydrolase mutant with improved catalytic activity for the hydrolysis of the P-S bond of phosphothiolester neurotoxins including VX and R-VX nerve gases to develop a novel, mediator-free, membrane-free biosensor for V-type nerve agents. The applicability of the biosensor was demonstrated for direct, rapid, and selective detection of V-type nerve agents' mimic demeton-S. The selectivity of the sensor against interferences and application to spiked lake water samples was demonstrated.

Adsorptive Stripping Voltammetric Determination of Amitrole at a Multi‐Wall Carbon Nanotubes Paste Electdrode

AbstractThis work reports the excellent electrocatalytic activity of carbon nanotubes paste electrodes (CNTPE) prepared by dispersion of multi‐wall carbon nanotubes (MWNT) within mineral oil toward the oxidation of 3‐amino‐1H‐1,2,4‐triazole (amitrole). The quantification is performed by adsorptive stripping voltammetry (AdSV). The influence of the paste composition and surface pretreatments as well as the amitrole accumulation conditions on the adsorption and further electrooxidation of this herbicide is described. After potentiodynamic pretreatment in 0.050 M phosphate buffer pH 7.4 the amitrole oxidation signal shifts 250 mV toward more negative potential and the sensitivity increases 29 fold, demonstrating that pretreated CNTPEs are extremely useful for a highly sensitive determination of amitrole down to the sub‐μM levels. The oxidation peak current is proportional to the amitrole concentration over the range from 0.8 to 7.0 μM (5 min accumulation), with a detection limit of 0.6 μM (48 μgL−1) and a precision of 4.3%, n=20. The proposed method was used for the determination of amitrole in spiked river water (Alberche River (Madrid, Spain)) and tap water samples (Madrid, Spain) at levels higher than 0.6 μM.

Enzymatic Biosensors Based on Carbon Nanotubes Paste Electrodes

AbstractThe performance of enzymatic biosensors based on the immobilization of different enzymes within a carbon nanotubes paste electrode (CNTPE) prepared by dispersion of multi‐wall carbon nanotubes (MWNT) and mineral oil is reported in this work. The strong electrocatalytic activity of carbon nanotubes towards the reduction of hydrogen peroxide and quinones and the oxidation of NADH have allowed an effective low‐potential amperometric determination of lactate, phenols, catechols and ethanol, in connection with the incorporation of lactate oxidase, polyphenol oxidase and alcohol dehydrogenase/NAD+, respectively, within the composite matrix. Compared to the analogous enzymatic CPEs, a great enhancement in the response is observed at the enzymatic CNTPEs. Therefore, highly sensitive lactate, phenols, catechols and alcohols biosensors without using any metal or redox mediator can be obtained with this new composite material.