Electrodeposition of cobalt oxide nanoparticles on carbon nanotubes, and their electrocatalytic properties for nitrite electrooxidation

We describe a modified glassy carbon electrode (GCE) for the sensitive determination of nitrite in waste water samples. The GCE was modified by electrodeposition of cobalt oxide nanoparticles on multi-walled carbon nanotubes (MWCNTs) deposited on a conventional GCE. Scanning electron microscopy and electrochemical techniques were used for the characterization of the composite material which is very uniform and forms a kind of nanoporous structure. Electrochemical experiments showed that the modified electrode exhibited excellent electrocatalytic properties for nitrite. Amperometry revealed a good linear relationship between peak current and nitrate concentration in the 0.5 to 250???M range with a detection limit of 0.3???M (S/N?=?3). The method has been applied to the amperometric detection of nitrite. The modified electrode displays good storage stability, reproducibility, and selectivity for a promising practical application.

磷化钴/多壁碳纳米管的制备及电催化性能研究

不断增加的能源需求和环境污染危机推动了替代高效能源转换和储存技术的广泛研究。电催化分解水具有潜在的应用前景,其可以利用电能获得清洁无污染的氢能。鉴于此,本论文通过不同浓度KOH浸泡超声的多壁碳纳米管(MWNT_S)作为基底,CoCl₂溶液为反应液,运用水热与固体磷化法得到负载有CoP的多壁碳纳米管材料。通过X-射线粉末衍射仪(XRD)、冷场发射扫描电子显微镜(SEM)、比表面及孔隙度分析(BET)对复合材料的晶型、形貌和比表面积进行了分析;通过电化学工作站对其相关电学性能进行了测试。实验结果表明在浓度为1 mol·L^-1 KOH浸泡的碳纳米管吸附的CoP含量最高(CoP-MWNTS-1.0),且电催化性能最佳,其在10 mA·cm²的电流密度下过电势为196 mV,Tafel斜率为231.07 mV/dec。     

Control growth of uniform platinum nanotubes and their catalytic properties for methanol electrooxidation

Uniform platinum nanotubes have been synthesized by directly mixing Ag nanowires and H₂PtCl₆ in saturated NaI solutions at room temperature. The crystal structure of the obtained Pt nanotube has been investigated in detail by field-emission scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. Furthermore, their electrocatalytic behaviors for methanol oxidation in alkaline media have also been studied. Compared with conventional Pt/C catalysts, these hollow nanostructures possess high electrochemical active areas and demonstrate higher current densities.     

Nonlinear optical properties of carbon nitride nanotubes

The second order polarizabilities (β) of the C(3)N(4) NT systems were investigated in this study. The β values of end groups substituted C(3)N(4) NTs were calculated to find their most favorable paradigm for nonlinear optical design. It was found that their electric dipole transitions are only allowed along the tube axis direction and the position of terminal groups has a great effect on NLO properties of substituted C(3)N(4) NTs. The obtained results provide us details to understand the relation between the structure and nonlinear optical properties. The results indicate that the second-order polarizabilities originate from charge transfer from a donor (-NH(2)) to an acceptor (-O(2)N) and the electron density redistribution in heptazine units. We employ a one-dimensional two-state model to analyze the nature of the second-order polarizabilities of studied materials. The frequency-dependent second-order polarizabilities were also calculated. The second-order polarizability of the O(2)N-C(3)N(4)-NH(2) NT is 2.51 × 10(-27) esu when the input photon energy is 2.232 eV, which is much larger (about two orders of magnitude) than static second-order polarizability (2.54 × 10(-29)).     

Enhanced stability and activity of PtRu nanotubes for methanol electrooxidation

PtRu 1D nanostructures on titanium are prepared and analysed as electrocatalysts for methanol electrooxidation. The morphology and composition of the 1D nanostructure are characterized by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The electrocatalytic properties of such catalysts for methanol oxidation are investigated by cyclic voltammetry (CV) and chronoamperometry (CA) in 1.0 M CH₃OH + 0.5 M H₂SO₄ aqueous solution. The results show that Pt₄₆Ru₅₄ nanotubes yields to a five-fold improvement of the mass specific activity and to a three-fold improvement of the long-term poisoning rate as compared to PtRu black of similar composition.     

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.     

Synthesis,structural characterization,and immunological properties of carbon nanotubes functionalized with peptides

Carbon nanotubes (NTs) are becoming highly attractive molecules for applications in medicinal chemistry. The main problem of insolubility in aqueous media has been solved by developing a synthetic protocol that allows highly water-soluble carbon NTs to be obtained. As a result, biologically active peptides can be easily linked through a stable covalent bond to carbon NTs. We have demonstrated that a bound peptide from the foot-and-mouth disease virus, corresponding to the 141-159 region of the viral envelope protein VP1, retained the structural integrity and was recognized by monoclonal and polyclonal antibodies. In addition, this peptide-NT conjugate is immunogenic, eliciting antibody responses of the right specificity. Such a system could be greatly advantageous for diagnostic purposes and could find future applications in vaccine delivery.     

Synthesis of coin-like hollow carbon and performance as Pd catalyst support for methanol electrooxidation

The coin-like hollow carbon (CHC) has been synthesized by only using ethanol as the carbon source with a novel Mg/NiCl₂ catalytic system via a facile solvothermal method for the first time. The CHC synthesized at optimized conditions shows an average thickness of less than 154 nm and the coin diameter of 1–3 μm. The CHC is characterized by SEM, TEM, XRD and electrochemical techniques. Pd on CHC (denotes as Pd/CHC) electrocatalysts are prepared for methanol oxidation in alkaline media. The Pd/CHC electrocatalyst gives a mass activity of 2930 A g⁻¹ Pd for methanol oxidation against 870 A g⁻¹ Pd on Pd/C electrocatalyst. One main reason for the higher mass activity of the Pd/CHC is the higher electrochemical active surface area (EASA) of the Pd/CHC.     

Preparation and electrocatalytic properties of gold nanoparticles loaded carbon nanotubes

Here, we report a new method of preparation of gold nanoparticles loaded carbon nanotubes (Au/CNTs) and the eleltrocatalystic properties of the obtained Au/CNTs as composite catalyst. This method shows advantages as it is easy to wash sodium citrate and the particle size of Au nanoparticles could by controlled by pH.     

Synthesis and characterization of faceted hexagonal aluminum nitride nanotubes

The synthesis of the faceted single-crystalline h-AlN nanotubes with the length of a few micrometers and diameters from 30 to 80 nm is first reported. This provides an ideal substrate for the construction of GaN-based nanoheterostructures in future nanoelectronics. The experimental results suggest the further extensive experimental and theoretical studies on the promising nonlayered nanotubular structures.     

Robust selenium-doped carbon nitride nanotubes for selective electrocatalytic oxidation of furan compounds to maleic acid

Selective oxidation of biomass-derived furan compounds to maleic acid (MA), an important bulk chemical, is a very attractive strategy for biomass transformation. However, achieving a high MA selectivity remains a great challenge. Herein, we for the first time successfully designed and fabricated Se-doped graphitic carbon nitride nanotubes with a chemical formula of C_3.0N-Se_0.03. The prepared C_3.0N-Se_0.03 was highly efficient for electrocatalytic oxidation of various biomass-derived furan compounds to generate MA. At ambient conditions, the MA yield could reach 84.2% from the electro-oxidation of furfural. Notably, the substituents on the furan ring significantly affected the selectivity to MA, following the order: carboxyl group > aldehyde group > hydroxyl group. Detailed investigation revealed that Se doping could tune the chemical structure of the materials (e.g., C_3.0N-Se_0.03 and g-C₃N₄), thus resulting in the change in catalytic mechanism. The excellent performance of C_3.0N-Se_0.03 originated from the suitable amount of graphitic N and its better electrochemical properties, which significantly boosted the oxidation pathway to MA. This work provides a robust and selective metal-free electrocatalyst for the sustainable synthesis of MA from oxidation of biomass-derived furan compounds.

Biomass-derived furan compounds could be selectively electro-oxidized into maleic acid over a robust selenium-doped carbon nitride nanotube catalyst.     

PtRu nanoparticles supported on 1-aminopyrene-functionalized multiwalled carbon nanotubes and their electrocatalytic activity for methanol oxidation

A new synthesis method for the preparation of high-performance PtRu electrocatalysts on multiwalled carbon nanotubes (MWCNTs) is reported. In this method, bimetallic PtRu electrocatalysts are deposited onto 1-aminopyrene (1-AP)-functionalized MWCNTs by a microwave-assisted polyol process. The noncovalent functionalization of MWCNTs by 1-AP is simple and can be carried out at room temperature without the use of expensive chemicals or corrosive acids, thus preserving the integrity and the electronic structure of MWCNTs. PtRu electrocatalysts on 1-AP-functionalized MWCNTs show much better distribution with no formation of aggregates, higher electrochemically active surface area, and higher electrocatalytic activity for the electrooxidation of methanol in direct methanol fuel cells as compared to that on conventional acid-treated MWCNTs and carbon black supported PtRu electrocatalysts. PtRu electrocatalysts on 1-AP-functionalized MWCNTs also show significantly enhanced stability.     

Preparation and characterization of size-controlled silver nanoparticles decorated multi-walled carbon nanotubes and their electrocatalytic reduction properties for hydrogen peroxide

The well dispersed and size-controlled Ag nanoparticles decorated multi-walled carbon nanotubes (MWCNT) were synthesized by a simple chemical plating method. The oxidized MWCNT surfaces could get a more controlled and specific nucleation of Ag nanoparticles. The as-prepared nanocomposites were characterized by transmission electron microscopy, X-ray diffraction and cyclic voltammetry. Randles-Sevcik plot suggested that the reaction of the nanocomposites in alkaline solution was a diffusion-controlled process. The electrocatalytic reduction property toward H₂O₂ was also studied.     

Synthesis,characterization and the electrocatalytic application of prussian blue/titanate nanotubes nanocomposite

A novel kind of nanocomposite, titanate nanotubes (TNTs) decorated by electroactive Prussian blue (PB), was fabricated by a simple chemical method. The as-prepared nanocomposite was characterized by XRD, XPS, TEM, FT-IR and Cyclic voltammetry (CV). Experimental results revealed that PB was adsorbed on the surface of TNTs, and the adsorption capacity of TNTs was stronger than that of anatase-type TiO₂ powder (TNP). The PB-TNTs nanocomposite was modified onto a glassy carbon electrode and the electrode showed excellent electroactivity. The modified electrode also exhibited outstanding electrocatalytic activity towards the reduction of hydrogen peroxide and can serve as an amperometric sensor for H₂O₂ detection. The sensor fabricated by casting Nafion (NF) above the PB-TNTs composite film (NF/PB-TNTs/GCE) showed two linear ranges of 2 × 10^?5–5 × 10^?4 M and 2 × 10^?3–7 × 10^?3 M, with a detection limit of 1 × 10^?6 M. Furthermore, PB-TNTs modified electrode with Nafion (NF/PB-TNTs/GCE) showed wider linear range and better stability compared with PB-TNTs modified electrode without Nafion (PB-TNTs/GCE) and PB modified electrode with Nafion (NF/PB/GCE).     

Preparation and electrocatalytic properties of Pt-SiO2 nanocatalysts for ethanol electrooxidation

Due to their high stability in general acidic solutions, SiO(2) nanoparticles were selected as the second catalyst for ethanol oxidation in sulfuric acid aqueous solution. Pt-SiO(2) nanocatalysts were prepared in this paper. The micrography and elemental composition of Pt-SiO(2) nanoparticles were characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy, respectively. The electrocatalytic properties of Pt-SiO(2) nanocatalysts for ethanol oxidation were investigated by cyclic voltammetry. Under the same Pt loading mass and experimental conditions for ethanol oxidation, Pt-SiO(2) nanocatalysts show higher activity than PtRu/C (E-Tek), Pt/C (E-Tek), and Pt catalysts. Additionally, Pt-SiO(2) nanocatalysts possess good anti-poisoning ability. The results indicate that Pt-SiO(2) nanocatalysts may have good potential applications in direct ethanol fuel cells.     

Monodispersed platinum nanocubes for enhanced electrocatalytic properties in alcohol electrooxidation

We report Pt nanocubes of ～4.5 nm in size synthesized by thermal decomposition in the presence of PVP. The Pt cubic electrocatalysts with dominantly exposed {100} facets show much improved electrocatalytic activities in methanol, ethanol and formic acid electrooxidation.     

In situ chemical fabrication of polyaniline/multi-walled carbon nanotubes composites as supports of Pt for methanol electrooxidation

Science China Chemistry - In this study, platinum (Pt)-polyaniline(PANI)/MWNTs catalysts were synthesized by two sequential reactions. First, core-shell structural PANI/MWNTs composites were...     

The origin of the high performance of tungsten carbides/carbon nanotubes supported Pt catalysts for methanol electrooxidation

The Pt supported on WC modified MWCNT catalysts (PtWC/MWCNT) were synthesized by the combination of organic colloidal and intermittent microwave heating (IMH) methods for the first. The results proved the better performance of the PtWC/MWCNT catalyst than that of Pt/C for methanol oxidation in terms of the onset potential and peak current density. The synergistic effect between Pt nanoparticles and WC and the structure effect of the MWCNTs could be the reasons to result in the high activity. The CO stripping test provided the evidence that the onset potential shift for methanol oxidation is consistent with the reduction in the overpotential for the CO oxidation on PtWC/MWCNT catalyst. Therefore, the mechanism of the high performance for methanol oxidation on PtWC/MWCNT catalyst is probably the easier oxidation of CO-like species which cause high overpotential for further oxidation of methanol.     

High dispersion and electrocatalytic properties of palladium nanoparticles on single-walled carbon nanotubes

Palladium (Pd) nanoparticles were electrochemically dispersed on single-walled carbon nanotubes (SWNTs) by electroreduction of octahedral Pd(IV) complex formed on the SWNT surface. The structure and nature of the resulting Pd-SWNT composites were characterized by transmission electron microscopy and X-ray diffraction. The electrocatalytic properties of the Pd/SWNT electrode for hydrazine oxidation have been investigated by cyclic voltammetry; high electrocatalytic activity of the Pd/SWNT electrode can be observed. This may be attributed to the high dispersion of palladium catalysts and the particular properties of SWNT supports. The results imply that the Pd-SWNT composite has good potential applications in fuel cells.     

A strategy for the high dispersion of PtRu nanoparticles onto carbon nanotubes and their electrocatalytic oxidation of methanol

Carbon nanotubes (CNTs) were non-covalently functionalized by 1-pyrenecarboxaldehyde (PCA) via π-π stacking interactions. PCA not only acts as the reductant for the deposition of PtRu nanoparticles, but the oxidation product of PCA can also effectively anchor and stabilize the in-situ-produced PtRu?NPs on the surface of CNTs. Transmission electron microscopy demonstrates that PtRu?NPs are uniformly dispersed on the surface of CNTs with small particles sizes of about 1.7 nm. The obtained PtRu-NP/CNT composites have higher electrochemical surface areas, electrocatalytic activities, and better stability towards methanol oxidation compared to PtRu?NPs supported on pristine CNTs.