Microwave-irradiated synthesized platinum nanoparticles/carbon nanotubes for oxidative determination of trace arsenic(III)

Platinum nanoparticles/carbon nanotubes (Pt_nano/CNTs) were rapidly synthesized by microwave radiation, and applied for the oxidative determination of arsenic(III). The transmission electron microscopy (TEM) revealed the size of synthesized Pt nanoparticles with nominal diameter of 15 ± 3 nm. Pt_nano/CNTs modified glassy carbon electrode (Pt_nano/CNTs/GCE) exhibited better performance for arsenic(III) analysis than that of Pt nanoparticles modified GCE (Pt_nano/GCE) by electrochemical deposition or Pt foil electrode. Excellent reproducibility of the Pt_nano/CNTs/GCE was obtained with the relative standard deviation (RSD) of 3.5% at 20 repeated analysis of 40 μM As(III), while the RSD was 9.8% for Pt_nano/GCE under the same conditions. The limit of determination (LOD) of the Pt_nano/CNTs/GCE was 0.12 ppb, which was 1–2 orders of magnitude lower than that of Pt_nano/GCE or Pt foil electrode.     

Key Factors for Simultaneous Improvements of Performance and Durability of Core‐Shell Pt3Ni/Carbon Electrocatalysts Toward Superior Polymer Electrolyte Fuel Cell

It remains a big challenge to remarkably improve both oxygen reduction reaction (ORR) activity and long‐term durability of Pt?M bimetal electrocatalysts simultaneously in the harsh cathode environment toward widespread commercialization of polymer electrolyte fuel cells (PEFC). In this account we found double‐promotional effects of carbon micro coil (CMC) support on ORR performance and durability of octahedral Pt₃Ni nanoparticles (Oh Pt₃Ni/CMC). The Oh Pt₃Ni/CMC displayed remarkable improvements of mass activity (MA; 13.6 and 34.1 times) and surface specific activity (SA; 31.3 and 37.0 times) compared to those of benchmark Pt/C (TEC10E20E) and Pt/C (TEC10E50E‐HT), respectively. Notably, the Oh Pt₃Ni/CMC revealed a negligible MA loss after 50,000 triangular‐wave 1.0–1.5 V_RHE (startup/shutdown) load cycles, contrasted to MA losses of 40 % (TEC10E20E) and 21.5 % (TEC10E50E‐HT) by only 10,000 load cycles. It was also found that the SA increased exponentially with the decrease in the CO stripping peak potential in a series of Pt?M/carbon (M: Ni and Co), which predicts a maximum SA at the curve asymptote. Key factors for simultaneous improvements of performance and durability of core‐shell Pt₃Ni/carbon electrocatalysts toward superior PEFC is also discussed.     

Development of Pt-Co catalysts supported on carbon nanotubes using the polyol method—tuning the conditions for optimum properties

Pt alloys with transition metals supported on carbon substrates are used as improved cathode electrocatalysts for fuel cells. Enhanced catalytic activity is attributed to the structure (Pt-Pt bond distance) and/or electronic effect (Pt d-electron vacancy). This work focuses on the development of Pt₃Co/f-MWCNT catalysts (functionalized multiwalled carbon nanotubes [f-MWCNT]) using ethylene glycol as the dispersing and reducing agent. The aim is to in parallel achieve fine dispersion, quantitative deposition and alloy formation. As described herein, the pH value of the reaction suspension has a critical effect on the composition and morphology of the synthesized nanoparticles. High pH values favor the formation of Pt₃Co alloy, nevertheless negatively influencing the dispersion. A discussion is made on the reduction/deposition mechanism and how to control the conditions to result in optimum properties.     

Determination of selenium(IV) by anodic stripping voltammetry with an in situ gold-plated rotating glassy carbon disk electrode

The application of an in situ gold-plated glassy carbon disk electrode to the determination of selenium(IV) by anodic stripping voltammetry is described. A single anodic stripping peak is obtained for solutions containing less than 1 × 10^-6 M Se(IV). The minimum concentration detected was 2 × 10^-9 M Se(IV). The determination of selenium in NBS SRM 1577 (Bovine Liver) by anodic stripping voltammetry with an in situ goldplated rotating glassy carbon electrode yielded a value of 1.14 ± 0.07 μg Se g^-1 compared with a certificate value of 1.1 ± 0.1 μg Se g^-1.     

Fabrication of a novel nonenzymatic hydrogen peroxide sensor based on Se/Pt nanocomposites

A novel nonenzymatic hydrogen peroxide sensor was successfully fabricated based on the Se/Pt nanocomposites. The nanocomposites were constructed via a simple solvethermal method, and were confirmed by X-ray diffraction (XRD), energy-dispersive X-ray spectrometry (EDS), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Cyclic voltammetry (CV) was used to evaluate the electrochemical performance of the nanocomposites at glassy carbon electrode (GCE). The results indicated that the Se/Pt nanocomposites exhibited excellent electrocatalytic activity to the reduction of H₂O₂ and could be used to construct a hydrogen peroxide amperometric sensor with a low detection limit and wide responding range.     

Surface and chemical characteristics of platinum modified activated carbon electrodes and their electrochemical performance

Platinum (Pt) loaded activated carbons (ACs) were synthesized by the thermal decomposition of platinum (II) acetylacetonate (Pt(acac)₂) over chemically activated glucose-based biochar. The effect of Pt loading on surface area, pore characteristics, surface chemistry, chemical structure, and surface morphology were determined by various techniques. XPS studies proved the presence of metallic Pt⁰ on the AC surface. The graphitization degree of Pt loaded ACs were increased with the loaded Pt⁰ amount. The electrochemical performance of the Pt-loaded ACs (Pt@AC) was determined not only by the conventional three-electrode system but also by packaged supercapacitors in CR2032 casings. The capacitive performance of Pt@AC electrodes was investigated via cyclic voltammetry (CV), galvanostatic charge-discharge curves (GCD), and impedance spectroscopy (EIS). It was found that the Pt loading increased the specific capacitance from 51 F/g to 100 F/g. The ESR drop of the packaged cell decreased with the Pt loading due to the fast flow of charge through the conductive pathways. The results showed that the surface chemistry is more dominant than the surface area for determining the capacitive performance of Pt loaded AC-based packaged supercapacitors.     

Cathodic stripping voltammetric determination of selenium(IV) at a thin-film mercury electrode in a thiocyanate-containing electrolyte

The well-known method for the determination of selenium(IV), which is based on the cathodic stripping voltammetry of copper(I) selenide, has been adapted for application at the thin-film mercury electrode on glassy carbon (TFME). Insufficient reproducibility and sensitivity have been overcome by using a 0.1 mol/L HClO₄ electrolyte solution containing 0.02 mol/L thiocyanate ions. Thiocyanate ions have been found to increase the peak height of the selenium response and shift it to more positive potentials. This behaviour is explained by an adsorption of SCN^– at the interface glassy carbon/Cu₂Se and its action as an electron transfer catalyst between glassy carbon and copper(I) selenide. A 3σ-detection limit of 75 ng/L Se^(IV) has been achieved. The relative standard deviation is 5.2% at 5 μg/L selenium(IV). The influence of cadmium(II), arsenic(III), zinc(II), iron(III) and lead(II) ions on the selenium response has been studied. In case of lead ions, a new signal occurred at more negative potentials than the reduction of Cu₂Se. This signal, which is probably due to the reduction of PbSe, can also be used for the determination of selenium(IV).     

Selenium electrochemistry in choline chloride–urea deep eutectic electrolyte

The electrochemical behaviour of selenium in the deep eutectic solvent made of a 1:2 molar ratio of choline chloride and urea (ChCl–U) has been investigated at a polycrystalline gold electrode by voltammetry and chronoamperometry. In order to favour the deposition of grey selenium, selenium oxide was chosen as the solution precursor and a temperature range from 70 to 110 °C was selected. Cyclic voltammograms recorded in the 1:2 choline chloride–urea liquid containing 10 mM SeO₂ are strongly affected by the temperature. At 110 °C, three main cathodic responses are evidenced around ?0.075, ?0.2 and ?0.7 V. These cathodic peaks have been attributed respectively to the underpotential deposition (upd) of Se, the bulk deposition of Se and the cathodic stripping of selenium associated to the formation of Se(?II). Potentiostatic current transients obtained at 110 °C are indicative of a nucleation with diffusion-controlled growth mechanism for the selenium electrodeposition and support the formation of a upd layer preceding the bulk deposition. The dissolution transients triggered by double potential step perturbations could however not be interpreted on the basis of a similar formalism.     

Pt-Se纳米空球修饰玻碳电极上甲酸的电催化氧化

以无定形硒溶胶为模板制备了不同硒覆盖度(θSe)(θSe=0.49,0.39,0.06,0)的Pt-Se和Pt纳米空球(分别记为(Pt-Se)HN和PtHN),发展了利用亚硫酸盐彻底除去核壳纳米粒子上Se的方法.对获得的纳米空球进行了形貌和结构的表征,结果表明所制备的(Pt-Se)HN粒径均匀,分散性好,球壳呈多孔结构.以其作为电催化剂制备了(Pt-Se)HN修饰的玻碳(GC)电极((Pt-Se)HN/GC),利用常规电化学方法比较该电极与PtHN/GC和商用碳载铂(Pt/C)修饰GC(Pt/C/GC)电极对甲酸的催化氧化作用,发现对甲酸氧化的活性顺序为(Pt-Se)HN/GCPtHN/GCPt/C/GC.三种电极催化甲酸氧化的机理有所不同:前者更倾向于通过弱吸附中间体直接氧化成CO2的单途径机理进行,后两者则通过强吸附和弱吸附中间体的双途径机理进行.在一定Se覆盖度条件下,(Pt-Se)HN/GC对甲酸的氧化有助催化作用.     

Cyclic and stripping voltammetry of Se(+4) and Se(−2) at the HMDE in acidic media

Electroreduction of Se(+4) and electrooxidation of Se(?2) were studied at mercury electrodes in acidic media and an improved mechanism of the reduction process was proposed. This mechanism takes into account the fact that the reduction path is concentration-dependent. At lower concentrations of Se(+4), mercury selenide and hydrogen selenide are formed at various potentials. At higher Se(+4) concentrations the electrode quickly becomes covered by a rigid deposit of mercury selenide and then the reduction starts to proceed to elemental selenium. Another form of selenium was formed in the vicinity of the mercury surface due to a chemical reaction between H₂SeO₃ and H₂Se. Oxidation of hydrogen selenide proceeds similarly, in the sense that after coverage of the electrode surface by a deposit of mercury selenide the oxidation starts to proceed to elemental selenium. The cathodic stripping peak of mercury selenide can be obtained down to 2 × 10^?8M of Se(+4), but this peak is often split and therefore the determination of traces of Se(+4) by the cathodic stripping technique is cumbersome.     

Cathodic stripping voltammetric determination of selenium(IV) at a thin-film mercury electrode in a thiocyanate-containing electrolyte

The well-known method for the determination of selenium(IV), which is based on the cathodic stripping voltammetry of copper(I) selenide, has been adapted for application at the thin-film mercury electrode on glassy carbon (TFME). Insufficient reproducibility and sensitivity have been overcome by using a 0.1 mol/L HClO₄ electrolyte solution containing 0.02 mol/L thiocyanate ions. Thiocyanate ions have been found to increase the peak height of the selenium response and shift it to more positive potentials. This behaviour is explained by an adsorption of SCN^– at the interface glassy carbon/Cu₂Se and its action as an electron transfer catalyst between glassy carbon and copper(I) selenide. A 3σ-detection limit of 75 ng/L Se^(IV) has been achieved. The relative standard deviation is 5.2% at 5 μg/L selenium(IV). The influence of cadmium(II), arsenic(III), zinc(II), iron(III) and lead(II) ions on the selenium response has been studied. In case of lead ions, a new signal occurred at more negative potentials than the reduction of Cu₂Se. This signal, which is probably due to the reduction of PbSe, can also be used for the determination of selenium(IV). Received: 13 November 1996 / Revised: 19 December 1996 / Accepted: 24 December 1996     

PtIr/C Catalysts Synthesized by Electrochemical Dispersion Method for Proton Exchange Membrane Fuel Cells

PtIr/C electrocatalyst with the metal phase uniformly distributed over the carbon support surface and the average size of PtIr nanoparticles of 5.9 nm is synthesized by electrochemical dispersion of Pt₉₀Ir₁₀ alloy under the action of alternating pulse current. It is shown that the presence of iridium within the composition of a Pt/C catalyst lowers down the overpotential of CO oxidation and increases catalyst’s specific activity with respect to electrochemical oxidation of ethanol.     

Size‐Controllable Synthesis of Trimetallic RhPdPt Island‐Shaped Nanoalloys with Enhanced Electrocatalytic Performance for Ethanol Oxidation in Alkaline Medium

Size‐controllable, high‐yield, island‐shaped RhPdPt trimetallic nanocrystals with sub‐2.0 nm islands have been successfully synthesized through a facile aqueous solution approach. The results of X‐ray diffraction (XRD), energy‐dispersive X‐ray (EDX) line scanning and elemental mapping analysis showed the as‐synthesized RhPdPt nanocrystals are alloy structures. These island‐shaped RhPdPt trimetallic nanoalloys showed a composition‐dependent electrocatalytic performance for ethanol oxidation in alkaline medium. Due to the special structure and intermetallic synergies, the Rh₁₀Pd₄₀Pt₅₀ nanoalloys exhibited an enhanced catalytic activity and durability relative to island‐shaped Pd₅₀Pt₅₀ bimetallic nanoalloys and commercial Pt black. The peak current density for Rh₁₀Pd₄₀Pt₅₀ nanoalloys was 1.81 and 1.38 times that for commercial Pt black and Pd₅₀Pt₅₀ nanoalloys, respectively. In addition, the peak potential on Rh₁₀Pd₄₀Pt₅₀ nanoalloys decreased 42 mV relative to commercial Pt black and Pd₅₀Pt₅₀ nanoalloys.     

Enhanced electrochemical activity for ethanol oxidation on the carbon-supported Pt3Te nanocatalysts by addition of Ru

Ternary Pt–Te–Ru catalysts with different atomic ratios were synthesized by reducing the precursor with formic acid. The physical and electrochemical characterization of the Pt₃TeRu_0.25/C catalyst was performed by transmission electron microscopy (TEM), X-ray diffraction, energy-dispersive X-ray spectroscopy equipped with TEM (TEM-EDX), X-ray photoelectron spectrometer, ethanol oxidation, and CO stripping. In TEM images, the Pt₃TeRu_0.25/C nanoparticles with an average particle size of around 2.9 nm were well dispersed on the carbon support. The Pt₃TeRu_0.25/C catalyst was superior to the Pt₃Te/C catalyst in respect of catalytic activity, durability, and CO tolerance. The positive effect of the Ru presence in the Pt₃TeRu_0.25/C catalyst was ascribed to the interactions of Ru or Ru oxides.     

Electroanalytical Study of Methanol Oxidation and Oxygen Reduction at Carbon Nanohorns‐Pt Nanostructured Electrodes

This work reports a comprehensive electroanalytical study of carbon nanohorns (CNHs) in electrochemical applications. Compared to other types of carbons, the bare CNHs electrode exhibited higher peak current densities and lowest anodic peak‐to‐cathodic peak separation of less than 50 mV for the [Fe(CN)^4?]₆/[Fe(CN)^3?]₆ redox couple. Furthermore, CNHs exhibited excellent electrocatalyst supporting properties for porous Pt film towards methanol oxidation reaction reaching a peak current density of 127 mA cm^?2 or peak current mass activity 184 mA mg_Pt^?1. Regarding oxygen reduction reaction, an onset potential as positive as 0. 77 V vs. Ag/AgCl was achieved with CNHs/porous Pt film.     

Application of Carbon Paste Electrode Modified with Carbon Nanofibres/Polyaniline/Platinum Nanoparticles as an Electrochemical Sensor for the Determination of Bezafibrate

The present study deals with the development of an electrochemical sensor for quantitative determination of Bezafibrate (BZF) based on carbon nanofibers/polyaniline/platinum nanoparticles modified carbon paste electrode (CNF/PANI/Pt/CPE). BZF is a fibric acid derivative and is used largely in the treatment of lipid disorders. The nanocomposite was synthesized by in situ polymerization of aniline using ammonium persulphate and platinum nanoparticles were uniformly decorated on the CNF/PANI surface by reducing hexachloroplatinic acid using sodium borohydride. The electrochemical response of BZF at CNF/PANI/Pt/CPE was studied using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). The above study resulted into significant improvement of the electrochemical signal towards the oxidation of BZF, revealing that the oxidation process is highly favorable at the surface of modified electrode. The anodic peak current I_p (μA) is found to be linearly dependent on BZF concentration in the range of 0.025 μM to 100 μM with a detection limit of 2.46 nM. The practical analytical utilities of the sensor were investigated by performing the experiments on synthetic pharmaceutical formulations, human blood serum and urine samples which offered good recovery, suggesting the high efficacy and authenticity of CNF/PANI/Pt/CPE sensor for BZF determination.     

One‐Pot Synthesis of Pt–Co Alloy Nanowire Assemblies with Tunable Composition and Enhanced Electrocatalytic Properties

Three‐dimensional (3D) Pt‐based alloy nanostructures composed of one‐dimensional (1D) nanowires/nanorods have recently attracted significant interest as electrocatalysts. In this work, we report an effective solvothermal method for the direct preparation of 3D Pt–Co nanowire assemblies (NWAs) with tunable composition. The composition‐ and structure‐dependent electrocatalytic performance is thoroughly investigated. Because of the bimetallic synergetic effect and unique structural advantage, the as‐prepared 3D Pt₃Co NWA outperforms commercial Pt/carbon and Pt black catalysts and even 3D Pt NWA. The electrochemical results demonstrate that the 3D Pt₃Co NWA is indeed a promising electrocatalyst with enhanced catalytic activity and improved durability for practical electrocatalytic applications.     

Single-Cu-atoms anchored on 3D macro-porous carbon matrix as efficient catalyst for oxygen reduction and Pt co-catalyst for methanol oxidation

Single metal atoms immobilized on a carbon substrate are of great potential for enhancing the catalytic activities for oxygen reduction and methanol oxidation reactions（ORR/MOR） owing to the maximized atom utilization. Herein, single copper atoms（SCAs） are loaded on macro-porous nitrogen-doped carbon（Cu-NC） derived from zeolitic imidazolate framework-8（ZIF-8）, which are used as catalysts for ORR and Pt-supports for MOR. For ORR, the catalyst marked as Cu-NC-3 exhibits a higher peak potential of ...     

Electrocatalytic oxidation of methanol on Pt-Pd nanoparticles supported on honeycomb-like porous carbons in alkaline media

Honeycomb-like porous carbons (PCs) were synthesized using a facile self-assembly method with phenolic resin as the carbon source and tetraethyl orthosilicate (TEOS) as the silica source. The PCs were found to have a large BET surface area of 458 m² g^?1 and a partially graphitized structure. The obtained PCs were used as a support for various Pt-Pd bimetallic alloy catalysts employed for methanol oxidation in alkaline media. Compared with Pt supported on commercial Vulcan XC-72R carbon (Pt/C) and with the other Pt-Pd bimetallic alloy catalysts on PCs, Pt₃Pd₁ on PCs displayed the most negative onset potential for methanol oxidation and the highest steady-state current (2.04 mA cm^?2). This may be because the Pt₃Pd₁/PCs catalyst has the largest electrochemical active surface area (ESA), and because adding Pd to the catalyst improves the ability of the intermediate species to tolerate oxidation. The results show that the prepared Pt-Pd/PCs is a potential candidate for application as a catalyst in alkaline direct methanol fuel cells.     

铂-氢钨青铜电极的制备及对氢氧化的电催化

采用电化学还原法在表面改性的碳布上,通过改变催化剂沉积顺序及氢钨青铜沉积时间制备铂-氢钨青铜复合催化剂,所得电极作为质子交换膜燃料电池(PEMFC)阳极。利用X射线衍射(XRD)、热重分析(TG)、扫描电子显微镜(SEM)、循环伏安(CV)及单电池极化性能测试研究了催化剂的组成、沉积量、分散性及其对氢氧化的电催化活性。实验结果表明,氢钨青铜沉积时间及催化剂沉积顺序对电极催化性能有显著影响,当氢钨青铜沉积时间为10 min,先沉积氢钨青铜、后沉积铂所得Pt/HxWO3电极对氢氧化具有最佳的催化活性。适量的氢钨青铜才能与铂形成较好的协同催化效应。