A comparative study of the electrochemical properties of carbon nanotubes and carbon black

Advanced Pt/Ti(1-x)SnxO2-C Composite Supported Electrocatalyst with Functionalized Carbon for Sustainable Energy Conversion Technologies

Sn-doped TiO2-carbon composites were identified as promising multifunctional supports for Pt electrocatalysts, in which the oxide component enhances resistance against corrosion and strong metal-support interactions at the Pt-oxide boundary ensure high stability for the Pt nanoparticles. This work is devoted to the study of the influence of preliminary functionalization of the carbon on the properties of Pt/Ti0.9Sn0.1O2-C catalysts. The structural, compositional and morphological differences between the samples prepared using functionalized or unmodified carbon, as well as the effect of carbon pre-modification on the electrocatalytic behavior of the synthesized Pt catalysts, were investigated using TEM, XRD, XPS, nitrogen adsorption and electrochemical measurements. The presence of oxygen-containing functional groups on carbon treated with HNO3 and glucose leads to the formation of a homogeneous coating of the carbon with dispersed crystallites of mixed oxide. Elemental mapping revealed the proximity of Sn species with highly dispersed (2-3 nm) Pt particles. Notably, the electrochemical results indicated enhanced activity in CO electrooxidation for both functionalized and unmodified carbon-containing catalysts. An improvement in the 10,000-cycle long-term stability of the catalyst prepared using functionalized carbon was evident compared to the catalyst with untreated carbon or reference Pt/C.

Dual-roles of carbon black to accelerate phosphorus recovery as vivianite

Carbon materials have been confirmed to promote phosphorus recovery as vivianite through enhancing dissimilatory iron reduction (DIR), which alleviates phosphorus crisis. Carbon black (CB) exhibits contradictory dual roles of cytotoxicity inducer and electron transfer bridge towards extracellular electron transfer (EET). Herein, the effect of CB on vivianite biosynthesis was investigated with dissimilatory iron reduction bacteria (DIRB) or sewage. With Geobacter sulfurreducens PCA as inoculum, the vivianite recovery efficiency increased accompanied with CB concentrations and enhanced by 39 % with 2000 mg·L^-1 CB. G. sulfurreducens PCA activated the adaptation mechanism of secreting extracellular polymeric substance (EPS) to resist cytotoxicity of CB. While in sewage, the highest iron reduction efficiency of 64 % was obtained with 500 mg·L^-1 CB, which was appropriate for functional bacterial selectivity like Proteobacteria and bio-transformation from Fe(III)-P to vivianite. The balance of CB's dual roles was regulated by inducing the adaptation of DIRB to gradient CB concentrations. This study provide an innovative perspective of carbon materials with dual roles for vivianite formation enhancement.

Enhanced Direct Electron Transfer Mediated Contaminant Degradation by Fe(IV) Using a Carbon Black-Supported Fe(III)-TAML Suspension Electrode System

Iron complexes of tetra-amido macrocyclic ligands (Fe-TAML) are recognized to be effective catalysts for the degradation of a wide range of organic contaminants in homogeneous conditions with the high valent Fe(IV) and Fe(V) species generated on activation of the Fe-TAML complex by hydrogen peroxide (H₂O₂) recognized to be powerful oxidants. Electrochemical activation of Fe-TAML would appear an attractive alternative to H₂O₂ activation, especially if the Fe-TAML complex could be attached to the anode, as this would enable formation of high valent iron species at the anode and, importantly, retention of the valuable Fe-TAML complex within the reaction system. In this work, we affix Fe-TAML to the surface of carbon black particles and apply this "suspension anode" process to oxidize selected target compounds via generation of high valent iron species. We show that the overpotential for Fe(IV) formation is 0.17 V lower than the potential required to generate Fe(IV) electrochemically in homogeneous solution and also show that the stability of the Fe(IV) species is enhanced considerably compared to the homogeneous Fe-TAML case. Application of the carbon black-supported Fe-TAML suspension anode reactor to degradation of oxalate and hydroquinone with an initial pH value of 3 resulted in oxidation rate constants that were up to three times higher than could be achieved by anodic oxidation in the absence of Fe-TAML and at energy consumptions per order of removal substantially lower than could be achieved by alternate technologies.

Application of immobilized ZnO nanoparticles for the photocatalytic regeneration of ultrasound pretreated-granular activated carbon

In this study, the photocatalytic regeneration by ZnO was employed for the regeneration of the granular activated carbon (GAC) which was saturated with the reactive red 43. The ultrasound was applied as a pretreatment step due to the cleanup of the adsorbent surface and providing a higher surface area and adsorption capacity. According to the nitrogen gas adsorption-desorption results, the ultrasound pretreated-GAC had the highest surface area and the total pore volume. The SEM and XRD analyses confirmed the immobilization of ZnO nanoparticles on the GAC. Response surface methodology (RSM) was used to model and optimize the preparation of the granular activated carbon/ZnO nanocomposite. The sonication time, pH, GAC/ZnO ratio, and calcination temperature were used as four effective parameters on nanocomposite preparation. Optimum amounts of pH, GAC/ZnO ratio, calcination temperature, and sonication time were found to be equal to 4, 5, 300 °C, 210 min, respectively; in these conditions, 83.98% of the capacity of the exhausted granular activated carbon was regenerated. ANOVA results, high R², R²-adj values, and also normal and random distribution of residuals showed that application of RSM for the modeling and optimizing the preparation step of GAC/ZnO nanocomposite was successful.

Polyacetylene carbon materials: facile preparation using AlCl3 catalyst and excellent electrochemical performance for supercapacitors

Polyacetylene (PA) was synthesized for the first time under mild conditions via polymerization of acetylene in n-octane with AlCl₃ as a catalyst, whereby a series of PA-derived carbon materials were obtained. Their composition and structure were characterized and their electrochemical performance was evaluated systematically. It is found that acetylene gas at 1 MPa can polymerize explosively at room temperature under catalysis of AlCl₃, forming acetylene black-like PA and a great amount of H₂, while in the presence of n-octane solvent, acetylene polymerizes smoothly at higher temperature (30 to 300 °C), forming PA with a H(CH Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> CH)_nH structure. A series of PA-derived carbon materials are obtained by treating PA with KOH at 800 °C. The as-synthesizzed PA-100–KOH exhibits a high specific surface area (∼2500 m² g⁻¹), high specific capacitance (241 F g⁻¹ at a current density of 0.1 A g⁻¹ and 143 F g⁻¹ at 5 A g⁻¹), low AC resistance, and good cycling stability with 91.7% maintenance of capacity after 2000 cycles at a current density of 2 A g⁻¹. This paper provides a new method for the facile synthesis of PA and a novel carbon source for supercapacitor electrode materials with excellent electrochemical performance and practical application.

Polyacetylene (PA) was synthesized for the first time under mild conditions via polymerization of acetylene in n-octane with AlCl₃ as a catalyst, whereby a series of PA-derived carbon materials were obtained.

Platinum Electrodeposition on Unsupported Single Wall Carbon Nanotubes and Its Application as Methane Sensing Material

This paper reports the decoration of single wall carbon nanotubes (SWCNTs) with platinum (Pt) nanoparticles using an electrochemical technique, rotating disk slurry electrode (RoDSE). Pt/SWCNTs were electrochemically characterized by cyclic voltammetry technique (CV) and physically characterized through the use of transmission electron microscopy (TEM), energy dispersive spectroscopy - X-ray florescence (EDS-XRF) and X-ray diffraction (XRD). After characterization it was found that electrodeposited nanoparticles had an average particle size of 4.1 ± 0.8 nm. Pt/SWCNTs were used as sensing material for methane (CH4) detection and showed improved sensing properties in a range of concentration from 50 ppm to 200 ppm parts per million (ppm) at room temperature, when compared to other Pt/CNTs-based sensors. The use of this technique for the preparation of Pt/SWCNTs opens a new possibility in the bulk preparation of samples using an electrochemical method and thus their potential use in a wide variety of applications in chemical sensing, fuel cell and others.

Insights into the effects of functional groups on carbon nanotubes for the electrooxidation of methanol

Functionalized carbon nanotubes were used as a support for PtCo nanoparticles. Their performance as electrocatalysts for the electrooxidation of methanol was evaluated by cyclic voltammetry and in situ FTIR reflectance spectroscopy. The onset potentials for both the electrooxidation of methanol and the production of CO(2) shifted to less positive values for catalysts prepared with more oxygen groups on the support. Furthermore, the production of CO(2) was higher on catalysts prepared with functionalized carbon nanotubes. The functional groups play two different but complementary roles. On the one hand, they help to stabilize smaller PtCo particles of ca. 3 nm. On the other hand, they provide the -OH groups necessary for the total oxidation of methanol to CO(2) at potentials less positive than on nonfunctionalized supports. Remarkably, the consumption of carboxylic acid groups along with the production of water is observed in the infrared spectra of the functionalized supports recorded during the electrooxidation of methanol. This observation suggests that the -OH groups of the support can also react with methanol, forming water and an ester.

Electrochemical properties and myocyte interaction of carbon nanotube microelectrodes

Arrays of carbon nanotube (CNT) microelectrodes (nominal geometric surface areas 20-200 μm(2)) were fabricated by photolithography with chemical vapor deposition of randomly oriented CNTs. Raman spectroscopy showed strong peak intensities in both G and D bands (G/D = 0.86), indicative of significant disorder in the graphitic layers of the randomly oriented CNTs. The impedance spectra of gold and CNT microelectrodes were compared using equivalent circuit models. Compared to planar gold surfaces, pristine nanotubes lowered the overall electrode impedance at 1 kHz by 75%, while nanotubes treated in O(2) plasma reduced the impedance by 95%. Cyclic voltammetry in potassium ferricyanide showed potential peak separations of 133 and 198 mV for gold and carbon nanotube electrodes, respectively. The interaction of cultured cardiac myocytes with randomly oriented and vertically aligned CNTs was investigated by the sectioning of myocytes using focused-ion-beam milling. Vertically aligned nanotubes deposited by plasma-enhanced chemical vapor deposition (PECVD) were observed to penetrate the membrane of neonatal-rat ventricular myocytes, while randomly oriented CNTs remained external to the cells. These results demonstrated that CNT electrodes can be leveraged to reduce impedance and enhance biological interfaces for microelectrodes of subcellular size.

The electrochemical properties of carbon nanotubes and carbon XC-72R and their application as Pt supports§

The results of an investigation of two samples of commercial multi-walled carbon nanotubes and a sample of carbon black, in the raw and activated state, were presented in the lecture. The activation of the carbon materials led to the formation of an abundance of oxygencontaining functional groups on the surface, an increased electrochemically active surface area, an enhanced charge storage ability and a promotion of the electron-transfer kinetics. It was presented that the morphology of the carbon nanotubes is important for the electrochemical properties, because nanotubes with a higher proportion of edge and defect sites showed faster electron transfer and pseudocapacitive redox kinetics. Modification of oxidized nanotubes by ethylenediamine and wrapping by poly(diallyldimethylammonium) chloride led to a decrease in the electrochemically active surface area and to reduced electron-transfer kinetics. Pt nanoparticles prepared by the microwave-assisted polyol method were deposited at the investigated carbon materials. A much higher efficiency of Pt deposition was observed on the modified CNTs than on the activated CNTs. The activity of the synthesized catalyst toward electrochemical oxygen reduction was almost the same as the activity of the commercial Pt/XC-72 catalyst.