Highly active nitrogen-doped few-layer graphene/carbon nanotube composite electrocatalyst for oxygen reduction reaction in alkaline media

In this work the electrocatalysis of oxygen reduction on nitrogen-doped few-layer graphene/multi-walled carbon nanotube (FLG/MWCNT) composite catalyst has been investigated. These composite materials were prepared from different nitrogen precursors, acid-treated MWCNTs and graphene oxide (GO), which was synthesised from graphite by the modified Hummers’ method. Urea and dicyandiamide were used as nitrogen precursors and the doping was achieved by pyrolysing the mixture of GO and MWCNTs in the presence of these nitrogen-containing compounds at 800 °C. The N-doped composite catalyst samples were characterised by scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy, the latter method revealed successful nitrogen doping. The oxygen reduction reaction (ORR) was studied in 0.1 M KOH on glassy carbon electrodes modified with N-doped FLG/MWCNT electrocatalysts employing the rotating disk electrode (RDE) method. The RDE results indicated that these metal-free nitrogen-doped nanocarbon catalysts possess remarkable electrocatalytic activity towards the ORR in alkaline media similar to that of commercial Pt/C catalyst. The results obtained in this work are particularly important for the development of non-Pt cathode catalysts for alkaline membrane fuel cells.     

Surfactant stabilized Pt and Pt alloy electrocatalyst for polymer electrolyte fuel cells

A simple process for the synthesis of carbon supported Pt and Pt/Ru electrocatalysts was investigated. Borrowing from the homogeneous catalyst preparation, this process uses a surfactant as a stabilizer which prevents the metal colloids from aggregation during the reduction process without influencing the deposition of the colloids onto the carbon support. Chemical, morphological and crystallographic properties of the newly prepared electrocatalysts were characterized using various surface techniques including X-ray diffraction (XRD), Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). These techniques show that mono-size, well-dispersed metal colloids can be formed and successfully supported on the carbon black. Moreover, the size of metallic colloids prepared by this method can be manipulated by controlling the synthesis temperature and is independent of the catalyst loading. Electrochemical characterizations show that in comparison with commercial E-TEK electrocatalysts, surfactant-based Pt/C electrocatalysts possess similar catalytic activity in terms of oxygen reduction and higher CO tolerance performance can be obtained by the surfactant stabilized Pt,Ru/C.     

Pt-decorated nanoporous gold for glucose electrooxidation in neutral and alkaline solutions

Exploiting electrocatalysts with high activity for glucose oxidation is of central importance for practical applications such as glucose fuel cell. Pt-decorated nanoporous gold (NPG-Pt), created by depositing a thin layer of Pt on NPG surface, was proposed as an active electrode for glucose electrooxidation in neutral and alkaline solutions. The structure and surface properties of NPG-Pt were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and cyclic voltammetry (CV). The electrocatalytic activity toward glucose oxidation in neutral and alkaline solutions was evaluated, which was found to depend strongly on the surface structure of NPG-Pt. A direct glucose fuel cell (DGFC) was performed based on the novel membrane electrode materials. With a low precious metal load of less than 0.3 mg cm^-2 Au and 60 μg cm^-2 Pt in anode and commercial Pt/C in cathode, the performance of DGFC in alkaline is much better than that in neutral condition.     

A Wasted Material,Duck Blood,as a Precursor of Non‐Precious Catalyst for the Oxygen Reduction Reaction

Searching for non‐precious electrocatalysts with high performance to replace the expensive Pt‐based electrocatalysts for oxygen reduction reaction (ORR) is a key issue in the industrial‐scale application of fuel cells. In this study, we have reported the synthesis of an iron doped N‐containing carbon materials, derived from duck blood, a wasted material in the duck meat production, as a novel and cost‐effective catalyst in ORR. The as‐prepared electrocatalysts were characterized by means of powder X‐ray diffraction, scanning electron microscopy, Raman spectroscopy and X‐ray photoelectron spectrometer. In 0.1 mol L⁻¹ KOH solution, the ORR onset potential and the half‐wave potential for the iron doped N‐containing carbon materials are 33 mV and –120 mV respectively, which are close to those of commercial Pt/C (20 wt%). In addition, the iron doped N‐containing carbon materials exhibit excellent tolerance to methanol crossover, which makes it a promising electrocatalyst for ORR in fuel cell.     

CO oxidation on non-alloyed Pt and Ru electrocatalysts prepared by the polygonal barrel-sputtering method

The CO oxidation on non-alloyed Pt and Ru electrocatalysts prepared by the polygonal barrel-sputtering method was investigated. Samples were prepared by sputtering Pt and Ru separately at room temperature. From the X-ray diffraction (XRD) measurement of the sample prepared on a SiO₂ glass plate, it was found that the sputtered metals are non-alloyed. Subsequently, the non-alloyed Pt and Ru electrocatalysts were prepared by the polygonal barrel-sputtering method using carbon powder as a support. The XRD patterns of these samples showed a single and very broad peak supporting the hypothesis of the non-alloyed Pt and Ru. No separate Ru reflections were visible, which could be attributed to Ru particle sizes smaller than 4 nm, as obtained by transmission electron microscopy (TEM). CO oxidation on the non-alloyed Pt and Ru electrocatalysts were evaluated by CO stripping voltammetry. This measurement revealed that the lower peak potential of CO oxidation varies, depending on the Pt content and the sputtering order. In addition, it was assumed that the CO oxidation reaction site for non-alloyed Pt and Ru electrocatalyst has a limited area including direct contact sites between the Pt and Ru particles.     

Niobium Dioxide Facilitating Methanol Electrooxidation on Pt/C Catalyst by Synergistic Effect

In this work, Pt nanoparticles are deposited on NbO₂‐modified carbon composites and evaluated as promising direct methanol fuel cell (DMFC) electrocatalysts. Transmission electron microscopy (TEM) and X‐ray diffraction (XRD) indicate that Pt nanoparticles (about 2.5 nm) are uniformly dispersed on NbO₂‐modified carbon composites. Electrochemical measurements show that the mass activity toward methanol electrooxidation on Pt/NbO₂‐C is as high as 3.0 times that of conventional Pt/C. Meanwhile, the onset potential of CO oxidation is negatively shifted by about 46 mV as compared with that of Pt/C, which means that the synergistic effect between NbO₂ and Pt facilitates the feasible removal of poisoning intermediate CO during methanol electrooxidation. X‐ray photoelectron spectroscopy (XPS) characterizations reveal the electron transfer from Nb to Pt, which suppress the poisoning CO adsorption on Pt nanoparticles and facilitate methanol electrooxidation. NbO₂ nanoparticles facilitate methanol electrooxidation on Pt/C catalyst by synergistic effect and electronic effect, which represents a step in the right direction for the development of excellent fuel cell anode electrocatalysts.     

Influence of nickel on the electrochemical activity of PtRu/multiwalled carbon nanotubes electrocatalysts for direct methanol fuel cells

This paper presents the effect of Ni in PtRu electrocatalysts over multiwalled carbon nanotubes (MWCNT) utilized for the electro-oxidation of methanol with the purpose of increasing reaction activity and tolerance to carbon monoxide. Two kinds of MWCNT were prepared using the same technique but different catalytic agents, ferrocene, and nickelocene. MWCNT obtained from ferrocene were treated after the synthesis to eliminate amorphous carbon and Fe excess, while MWCNT from nickelocene were used as synthesized to leave the nickel nanoparticles formed during the synthesis. PtRu particles were deposited over the surface of both types of MWCNT in order to study the effect of the Ni presence. The structure of the electrocatalysts was analyzed by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Chemical elemental microanalysis was carried out by X-ray energy dispersive spectroscopy (EDS). The synthesized MWCNT had an average diameter in the order of 60 nm and an average length of about 30 microns. Metallic nanoparticles deposited had a particle size in the order of 10 nm each. The electrochemical surface area (ESA) was measured using CO stripping curves and the activity toward the methanol oxidation reaction was evaluated. The ESA was improved with the presence of Ni, achieving an activity and onset potential similar to a commercial electrocatalyst (20 wt% PtRu/C, ETEK) with a lower PtRu loading (10 wt% PtRu).     

Stabilization and dispersion of PtRu and Pt nanoparticles on multiwalled carbon nanotubes using phosphomolybdic acid,and the use of the resulting materials in a direct methanol fuel cell

PtRu and Pt nanoparticles were deposited on the surface of multiwalled carbon nanotubes (MWCNTs) with the assistance of phosphomolybdic acid (PMo) by a one-pot hydrothermal reduction strategy. Transmission electron microscopy shows a high-density PtRu (or Pt) nanoparticles uniformly dispersed on the surface of the MWCNTs with an average diameter of 1.8 nm for PtRu nanoparticles and 2.4 nm for Pt nanoparticles. Moreover, the as-prepared PMo/PtRu/MWCNT and PMo/Pt/MWCNT electrocatalysts are highly electroactive for the electrochemical oxidation of methanol. Cyclic voltammograms show a high electrochemical surface area (ESA) and a large current density for methanol oxidation at the modified electrode by PMo/PtRu/MWCNT and PMo/Pt/MWCNT electrocatalysts. Electrochemical impedance spectroscopy reveals a high CO tolerance for PMo/PtRu/MWCNT and PMo/Pt/MWCNT electrocatalysts in the electrochemical catalysis of methanol oxidation. For comparison, PtRu/MWCNT and Pt/MWCNT electrocatalysts were prepared in control experiments without PMo. The results demonstrate that PtRu and Pt nanoparticles deposited on MWCNTs in the presence of PMo were superior to those on MWCNTs without PMo in several respects including: (1) a smaller size and a higher dispersion; (2) a higher ESA; (3) a larger current density for methanol oxidation; (4) a higher tolerance for CO poisoning.     

Studies on the effect of solvent for the synthesis of low-cost and efficient Pt-Co/CAB cathode electrocatalyst to enhance the performance of a hydrogen-based PEMFC

Highly efficient and low-cost Pt-Co/C_AB bimetallic cathode electrocatalysts were synthesized for hydrogen-based proton exchange membrane fuel cell (PEMFC) using three different types of solvent, namely, dimethyl sulphoxide (DMSO), dimethylformamide (DMF), and ethylene glycol (EG). The physical characterization of synthesized cathode electrocatalysts Pt-Co/C_AB-DMSO, Pt-Co/C_AB-DMF and Pt-Co/C_AB-EG was performed by scanning electron microscope–energy-dispersive X-ray (SEM–EDX), X-ray diffraction (XRD), and transmission electron microscopy (TEM) techniques, whereas the electrochemical investigation of all three Pt-Co/C_AB electrocatalysts was performed by CV and EIS studies. The synthesized Pt-Co/C-EG electrocatalyst produced the highest power density of 19.61 mW/cm² at a room temperature of 33°C. The power density increased to 26.11 mW/cm², that is, 133%, when the cell operating temperature was raised from 33 to 70°C. The excellent performance of the Pt-Co/C_AB-EG cathode electrode proves that it can be recommended as a commercial electrocatalyst for PEMFC cathode. In addition, the EG/EG was identified as the best solvent for the synthesis of Pt-Co/C_AB cathode electrocatalysts.     

Templated Ru/Se/C electrocatalysts for oxygen reduction

Highly porous Ru/Se/C electrocatalysts have been successfully synthesized via a template-based method, which was carried out by the impregnation of a hard template (silica gel) with a mixture of RuCl₃·xH₂O, SeO₂ and sucrose dissolved in water. The resulting Ru/Se/C catalysts show good catalytic activity for oxygen reduction in acidic media. The electrocatalysts are believed to consist of selenium-modified ruthenium nanoparticles, which are embedded in a high surface area carbon matrix. The structural properties of the prepared Ru/Se/C electrocatalysts were investigated using nitrogen physisorption measurements, X-ray diffraction and transmission electron microscopy. The elemental composition of prepared Ru/Se/C electrocatalysts was determined using electron microprobe. The catalytic activity was tested using the rotating-ring-disk-electrode technique in 0.1 M HClO₄ solution at room temperature.     

In Situ Synthesis of Reduced Graphene Oxide and Gold Nanocomposites for Nanoelectronics and Biosensing

In this study, an in situ chemical synthesis approach has been developed to prepare graphene–Au nanocomposites from chemically reduced graphene oxide (rGO) in aqueous media. UV–Vis absorption, atomic force microscopy, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy were used to demonstrate the successful attachment of Au nanoparticles to graphene sheets. Configured as field-effect transistors (FETs), the as-synthesized single-layered rGO-Au nanocomposites exhibit higher hole mobility and conductance when compared to the rGO sheets, promising its applications in nanoelectronics. Furthermore, we demonstrate that the rGO-Au FETs are able to label-freely detect DNA hybridization with high sensitivity, indicating its potentials in nanoelectronic biosensing.     

Templating of electrodeposited platinum group metals as a tool to control catalytic activity

The present study is focused on the synthesis and investigation of Pt and Pt-Ru nanostructures templated by anodic aluminum oxide films. Samples of this sort may be considered in future as model electrode materials of high roughness and specific controllable nanostructural features. Nanostructure and morphology of electrodeposited materials are characterized using scanning electron microscopy and scanning tunneling microscopy techniques. A possibility to control catalytic activity of electrodeposits by means of templating is discussed as well. Higher catalytic activity of nanostructured Pt-Ru as compared to usual electrodeposit is very promising for further clarification of structural effects in electrocatalysis. In particular, newly proposed materials combine high roughness and the increased number of grain boundaries known to provide high catalytic activity of platinum group metals in certain processes. Future prospects of obtaining materials with even higher roughness factors are discussed.     

Effect of transition metals (Ni,Sn and Mo) in Pt5Ru4M alloy ternary electrocatalyst on methanol electro-oxidation

Pure Pt, PtRu and Pt₅Ru₄M (M = Ni, Sn and Mo) electrocatalysts were prepared using a NaBH₄ reduction method. The alloy formation and particle size of the electrocatalysts were determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. The formation of crystalline Pt was confirmed regardless of the addition of Ru and transition metals. The average particle size was found to be about 2.5–3.5 nm.The electrochemical properties of the electrocatalysts were analyzed by methanol electro-oxidation and CO stripping in the half cell. The mass activity and specific activity were obtained through these experiments. Methanol electro-oxidation and the specific activity of the PtRuNi electrocatalyst were much higher than that of PtRu electrocatalyst. The specific activity of methanol electro-oxidation based on EAS for the PtRuSn and PtRuMo electrocatalysts was higher than that of the PtRu, although their mass activity of methanol electro-oxidation was lower.     

Periodic organosilica hollow nanospheres as anode materials for lithium ion rechargeable batteries

Polymeric micelles with core-shell-corona architecture have been found to be the efficient colloidal templates for synthesis of periodic organosilica hollow nanospheres over a broad pH range from acidic to alkaline media. In alkaline medium, poly (styrene-b-[3-(methacryloylamino)propyl] trimethylammonium chloride-b-ethylene oxide) (PS-PMAPTAC-PEO) micelles yield benzene-silica hollow nanospheres with molecular scale periodicity of benzene groups in the shell domain of hollow particles. Whereas, an acidic medium (pH 4) produces diverse hollow particles with benzene, ethylene, and a mixture of ethylene and dipropyldisulfide bridging functionalities using poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) (PS-PVP-PEO) micelles. These hollow particles were thoroughly characterized by powder X-ray diffraction (XRD), dynamic light scattering (DLS), thermogravimetric analysis (TG/DTA), Fourier transformation infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), magic angle spinning-nuclear magnetic resonance ((29)Si MAS NMR and (13)CP-MAS NMR), Raman spectroscopy, and nitrogen adsorption/desorption analyses. The benzene-silica hollow nanospheres with molecular scale periodicity in the shell domain exhibit higher cycling performance of up to 300 cycles in lithium ion rechargeable batteries compared with micron-sized dense benzene-silica particles.     

Pd–Co/MWCNTs Catalyst for Electrooxidation of Hydrazine in Alkaline Solution

Multiwall carbon nanotubes supported Pd–Co electrocatalysts (Pd–Co/MWCNTs) for hydrazine electrooxidation in alkaline electrolytes were prepared. Their morphology and structure were characterized by scanning electron microscopy, transmission electron microscope, and X‐ray diffraction. The effect of the mass ratio of Pd to Co on the catalytic performance was examined via cyclic voltammetric and chronoamperometric measurements. The Pd–Co/MWCNTs with a mass ratio of 1:1 for Pd:Co shows higher catalytic performance than both Pd/MWCNTs and Co/MWCNTs and it has good stability for catalyzing the electrooxidation of hydrazine. The gas collection measurements indicated that hydrazine electrooxidation on Pd–Co/MWCNTs proceeded via a near 4‐electron pathway.     

Ni-Fe基析氧阳极材料的研究进展

寻找一种高效、稳定和低成本的析氧阳极材料对于在碱性环境中电解水的研究具有非常重要的实际意义。近年来,Ni-Fe基材料以其低成本及在碱性条件下具有高催化活性的特点成为析氧反应电极材料的研究热点。本文概述了近几年国内外学者对不同的Ni-Fe基析氧材料(包括Ni-Fe合金、Ni-Fe氧化物、Ni-Fe层状双金属氢氧化物及Ni-Fe基复合材料等)在合成方法、物理形态、化学结构和催化性能等方面所进行的研究,介绍了Ni-Fe基材料的析氧反应机理的进展,探究了析氧反应活性相以及Fe的掺入对Ni基氢氧化物的结构和活性的影响,最后指出了合成方法的改进及详细反应机理的探究将会成为未来Ni-Fe基析氧阳极材料的重点研究方向。     

不同浸渍时间对CuO/Cu@BC电极催化CO2还原性能的影响

将具有3D网状结构的细菌纤维素(BC)膜作为催化剂载体,通过原位化学还原法制备了负载Cu和CuO纳米复合材料的催化剂电极(CuO/Cu@BC),并通过改变BC膜的浸渍时间实现电极结构调控以探索最佳条件。结果表明,具有3D球形结构的CuO/Cu24h@BC电极对CO2还原表现出较好的电子传输性能和更高的电流密度。CuO/Cu24h@BC电极的电化学比表面积最大,达12 mF/cm2。CuO/Cu24h@BC电极可将CO2电催化转化为CO,且产生CO的法拉第效率为52%。     

Experimental and density functional theory studies on PtPb/C bimetallic electrocatalysts for methanol electrooxidation reaction in alkaline media

Carbon-supported bimetallic Pt_mPb₁ (m = 1, 2, 3) electrocatalysts with different Pt/Pb atomic ratios were synthesized by a polyol method. The X-ray diffraction results reveal that a PtPb alloy formed in the Pt_mPb₁/C electrocatalysts. TEM images show that the PtPb nanoparticles distribute uniformly on the carbon support, and are about 4–5 nm in size. The Pt_mPb₁/C bimetallic catalysts show superior activities toward methanol electrooxidation reaction (MOR) than the Pt/C in alkaline media. Both CO stripping measurements and density functional theory studies reveal that CO adsorption decreased significantly on the Pt_mPb₁/C bimetallic catalysts compared with on pure Pt, which may offer an explanation for the enhanced MOR activity of the Pt_mPb₁/C bimetallic catalysts.     

Synthesis, Characterization and Catalytic Properties of Coordination Complexes Based on [Mo(CO)3(CH3CN)3] and Poly(4-vinylpyridine)

The synthesis, characterization, and catalytic properties of the zero-valent, group six metal complex formed by the reaction of [Mo(CO)₃(CH₃CN)₃] and poly(4-vinylpyridine) (P(4-VP)) is described in this work. The pyridyl groups of the organic polymer are covalently bonded to the Mo centers as suggested by X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and Fourier transform infrared (FT-IR) techniques. The polymer-immobilized metal catalyst was also characterized by DTA–TGA, differential scanning calorimetry (DSC) analysis and its morphology and elemental analyses were studied by scanning electron microscopy/energy dispersive X-ray (SEM/EDX) techniques. In the presence of 2-ethoxyethanol the solid is an active catalyst for the heterogeneous hydrogenation of styrene to ethyl benzene.