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The primary issue for the commercialization of proton exchange membrane fuel cells (PEMFCs) is the carbon corrosion of support and dissolution agglomeration of platinum nanoparticles under start-up/shut-down (SU/SD) conditions. Carbon nanotubes (CNTs)-supported Pt nanowire (PtNW) catalyst toward the ORR was synthesized via the soft template method. Electrochemical characterization demonstrated that the PtNW/CNTs showed higher activity than Pt/C because the anisotropy of the 1D structure strengthened its ability to transport electrons. An accelerated stressed test between 1.0 and 1.5 V for carbon corrosion was performed to examine durability at a single cell under practical SU/SD conditions. After 5000 cycles, the voltage drop was 0.142 V, and the voltage decay rate was 0.0284 mV cycle−1 for the PtNW/CNTs catalyst at 1600 mA cm−2; the voltage drop was 0.417 V, and the voltage decay rate was 0.0834 mV cycle−1 for the Pt/C catalyst at 1600 mA cm−2. The Pt/C catalyst demonstrated severe Pt nanoparticle aggregation and growth with a wide size distribution, whereas the PtNW/CNTs catalyst showed a slight variation. The PtNW/CNTs catalyst showed remarkable durability after 5000 SU/SD cycles. Consequently, PtNW/CNTs is a promising electrocatalyst, which can replace traditional Pt/C catalyst in PEMFCs. • PtNW/CNTs were synthesized using the soft template method with CNTs as support. • The start-up/shut-down event was analyzed and simulated with a measurable protocol. • The ORR activity and the electrochemical stability of the PtNW/CNTs catalyst were remarkably improved. • The PtNW/CNTs catalyst has better performance and life of single cell than the Pt/C catalyst. [ABSTRACT FROM AUTHOR]

Dopamine is an important neurotransmitter in the body and closely related to many neurodegenerative diseases. Therefore, the detection of dopamine is of great significance for the diagnosis and treatment of diseases, screening of drugs and unraveling of relevant pathogenic mechanisms. However, the low concentration of dopamine in the body and the complexity of the matrix make the accurate detection of dopamine challenging. Herein, an electrochemical sensor is constructed based on ternary nanocomposites consisting of one-dimensional Pt nanowires, two-dimensional MXene nanosheets, and three-dimensional porous carbon. The Pt nanowires exhibit excellent catalytic activity due to the abundant grain boundaries and highly undercoordinated atoms; MXene nanosheets not only facilitate the growth of Pt nanowires, but also enhance the electrical conductivity and hydrophilicity; and the porous carbon helps induce significant adsorption of dopamine on the electrode surface. In electrochemical tests, the ternary nanocomposite-based sensor achieves an ultra-sensitive detection of dopamine (S/N = 3) with a low limit of detection (LOD) of 28 nM, satisfactory selectivity and excellent stability. Furthermore, the sensor can be used for the detection of dopamine in serum and in situ monitoring of dopamine release from PC12 cells. Such a highly sensitive nanocomposite sensor can be exploited for in situ monitoring of important neurotransmitters at the cellular level, which is of great significance for related drug screening and mechanistic studies. [Display omitted] • Pt/MX binary composites by solvothermal synthesis. • Pt/MXPC ternary nanocomposites by mixing Pt/MX binary composites and PC. • Pt/MX/PC-modified SPCEs for electrochemical detection of dopamine. • In situ monitoring of dopamine released from PC12 cells by K+ stimulation. [ABSTRACT FROM AUTHOR]

The activity of catalyst could be enhanced by the temperature rising, so it is a suitable way to reduce the noble metal loading for the catalyst. However, the corrosion of carbon supports will be remarkable in the high temperature proton exchange membrane fuel cells (HT-PEMFC, >100 °C). This report demonstrated a novel Ti 3 C 2 T x and CNT hybrid material as the catalytic support, and Pt nanowires (Pt NWs) is loaded on the hybrid support to construct the catalyst for HT-PEMFC. The Pt NWs/Ti 3 C 2 T x -CNT performs higher electrochemical activity, better stability than that of commercial Pt/C. The mass activity and specific activity of Pt NWs/Ti 3 C 2 T x -CNT catalysts are 3.89 and 3.02 times as that of Pt/C, respectively. The power densities of HT-PEMFC showed 155.4 mW cm−2 and 182 mW cm−2 at 150 and 180 °C, respectively. • The mass activity of Pt NWs/Ti3C2Tx-CNT is 3.89 times as that of Pt/C. • The catalyst superior performance is mainly ascribed to the synergistic effect. • The peak power density based on Pt NWs/Ti3C2Tx-CNT achieves 182 mW cm-2 at 180 °C. [ABSTRACT FROM AUTHOR]

Electrochemical reduction of CO2 to the value‐added fuels is a promising way to mitigate global warming. However, conversion of CO2 to methanol or formic acid is very challenging due to the poor performance of the catalysts employed for the reduction of CO2. In this work, higher performance toward CO2 reduction was obtained when Pt nanowire (Pt NW) assembly is utilized as a co‐catalyst in the electrochemical reduction of CO2 activated by pyridinium (PyrH+). It is found that the overall Faraday efficiency for CO2‐derived products is 55%. The methanol and formic acid were the only detected compounds in aqueous solution using high performance liquid chromatography. Results of this research showed that the higher hydride accumulation on Pt NW and its morphological advancements are two major factors for superior electrochemical performance in CO2 electroreduction. © 2018 American Institute of Chemical Engineers Environ Prog, 38: 112–117, 2019 [ABSTRACT FROM AUTHOR]

Abstract Improving cathode performance at a lower Pt loading is critical in commercial PEMFC applications. A novel Pt nanowire (Pt-NW) cathode was developed by in-situ growth of Pt nanowires in carbon matrix consisting Pt nanoparticles (Pt-NPs). Characterization of TEM and XRD shows that the pre-existing Pt-NPs from Pt/C affect Pt-NW morphology and crystallinity and Pt profile crossing the matrix thickness. The cathode with Pt-NP loading of 0.005 mg Pt-NP cm−2 and total cathode Pt loading of 0.205 mg Pt cm−2 has the specific current density of 89.56 A g Pt −1 at 0.9 V, which is about 110% higher than that of 42.58 A g Pt −1 of the commercial gas diffusion layer (GDE) with Pt loading of 0.40 mg cm−2. When cell voltage is below 0.48 V, the Pt-NW cathode has better performance than the commercial GDE. It is believed that the excellent performance of the Pt-NW cathode is attributed to Pt-NP induction, therefore producing unique Pt-NW structure and efficient Pt utilization. A Pt-NW growth mechanism was proposed that Pt precursor diffuses into the matrix consisting of pre-existent Pt-NPs by concentration driving, and Pt-NPs provide priority sites for platinum depositing at early stage and facilitate Pt-NW growth. Graphical abstract Pt nanoparticles in carbon matrix enhance growth, uniformity and profile of Pt-NWs, and the Pt-NW electrodes behave high performance. Image 1 Highlights • Pt nanoparticles in the carbon matrix improve uniformity and profile of Pt-NWs. • The novel cathode with 0.205 mg Pt cm−2 is comparable to commercial one. • A Pt-NW growth mechanism in the porous matrix is proposed. • This work provides a strategy for tailoring the electrode architectures. [ABSTRACT FROM AUTHOR]

Herein, we report a universal approach for fabricating mesoporous Pt nanowires with controlled mesostructures from a dual template using anodic aluminum oxide (AAO) membrane with silica nanospheres assembled in the channels. The mesoporous Pt nanowires with well-ordered mesopores are successfully prepared by chemical reduction deposition method. In addition, we show a variety of mesopore arrangements in the Pt nanowires (such as linear, zigzag, and meshy topologies) for different values of the D (the ratio of the AAO channel ( d 1 ) and silica sphere diameter ( d 2 )) factor ranging between 1 and 1+ 2 (≈2.414). The present approach is anticipated to work on the preparation of mesoporous nanowires of other metals (e.g., Au, Ni, and Pd) or alloys (e.g., Pt-Ni and Pt-Ru alloys) with various topologies that may be promising as potential candidates for the next generation nanodevices and other applications (e.g., fuel cells and catalysis). [ABSTRACT FROM AUTHOR]

Catalyst layers play an important role in direct methanol fuel cells (DMFCs), providing the reaction sites and catalysing the electrochemical reactions. For gas diffusion electrodes with Pt nanowires in-situ grown on gas diffusion layers (GDLs), the hydrophobic property of the GDL surface negatively affects the growth of the Pt nanowire catalysts, leading to the unsatisfied catalysis performance. In this work, the influence of active screen plasma (ASP) treatment temperature and duration on the growth of Pt nanowire catalyst layer was systemically studied. Single cell performance test with in-situ electrochemical surface area (ECSA) measurement were conducted to evaluate the catalysis performance of the Pt nanowire catalyst layer grown on the ASP treated carbon paper; scanning electron microscopy (SEM) was used to observe the surface morphology of the catalyst layer formed. Results revealed that the ASP treatment conducted at 120 °C for 10 min can effectively promote the growth of Pt nanowires on carbon paper gas diffusion layer, which exhibited the best catalysis performance. [ABSTRACT FROM AUTHOR]

The cathode electrocatalyst layers were prepared by in situ growing Pt nanowires (Pt-NWs) in two kinds of matrixes with various Pt loadings for proton exchange membrane fuel cells (PEMFCs). Commercial carbon powder and 20 wt.% Pt/C electrocatalyst were used as the matrix material for the comparison. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), polarization curves tests, and electrochemical impedance spectroscopy (EIS) were carried out to examine the effects of the matrix materials on the Pt-NW growing and the electrode performance. The optimum Pt-NW loadings of 0.30 mg cm−2 in the carbon matrix (CM) and 0.20 mg cm−2 for the Pt/C matrix (PM) were obtained. The results indicated that the Pt-NWs grown in the CM had a better crystalline, longer size length and better catalyst activity than those in the PM. The mechanism of the matrix affection is further discussed in this paper. [ABSTRACT FROM AUTHOR]

The anisotropic structure and unique surface properties of one-dimensional (1D) Pt-nanowire (PtNW) make it a promising new type of electrocatalyst for various catalyst applications, especially for fuel cells. However, due to the critical synthesis process, a finely tuning of the synthesis temperature for precisely controlling the morphology and distribution of PtNWs in catalyst electrodes still remains a grand challenge. In this work, we present the temperature-controlled growth of PtNWs with large-area 16 cm 2 carbon paper piece as a direct support. The relationship between the growth temperature and PtNW behavior is studied by physical characterization, and their catalytic activity is measured towards oxygen reduction reaction (ORR) by testing as the cathode in a hydrogen-air fuel cell. The results show that the growth temperature plays a vital role on the behavior of PtNWs thus influencing their properties. The catalyst electrode with PtNWs grown at 40 °C shows the best power performance. A possible mechanism for the influence of temperature on PtNW growth is suggested. The comparison with the state-of-the-art commercial TKK catalyst also shows a better performance and durability. The understanding gained in our work from PtNW catalyst electrode could aid in the design of other novel nanostructures in practical applications. [ABSTRACT FROM AUTHOR]

A gradient Pt nanowire (Pt-NW) cathode with a promoted mass transfer and Pt utilization was developed by decal transfer method. The relationships of Pt loading and ionomer content with electrode performance were investigated by electrode structure characterization and testing in polymer electrolyte membrane fuel cell (PEMFC). The results show that an increasing Pt loading can improve the catalytic kinetic performance of Pt-NW electrode, but too higher a Pt loading leads to serious aggregation and thus low catalyst utilization. A similar trend was found to the ionomer content sprayed onto the Pt-NW cathode. The ionomer extends the triple-phase boundary (TPB), but excessive amount would cover part of the catalyst active sites and hinder the mass transfer. The optimal performance of the Pt-NW cathode is achieved at 0.30 mg Pt cm −2 and 33 wt% ionomer, where a maximum power density of 0.93 W cm −2 is obtained, which is better than the state-of-the-art commercial gas diffusion electrode (GDE) with 0.40 mg Pt cm −2 . [ABSTRACT FROM AUTHOR]

Surface roughed platinum (Pt) nanowires,which have been synthesized by a galvanostatic electrodeposition method in a nanoporous template, were applied as electrocatalysts for methanol oxidation reaction. The experimental results showed that the surface roughness of the Pt nanowires (correspondingly the surface morphology and grain size) has a dramatic effect on their catalytic property. From cyclic voltammetry and chronoamperometric measurements, the surface roughed Pt nanowires presented better activity (109.5 mA mg -1 ) and higher stability for methanol oxidation than the surface smooth Pt nanowires. From the electrochemical impedance spectroscopy (EIS) measurements, the surface roughed Pt nanowires showed higher electrical conductivity and more efficient electrochemical performance than the surface smooth nanowires. The experimental results indicated that both the increased surface area and larger crystal grain size of the surface roughed nanowires contributed to improved catalytic performance. The surface roughed Pt nanowires showed great promise in many important applications such as catalysis and fuel cells. [ABSTRACT FROM AUTHOR]

Periodic twins are an intrinsic structural feature of some types of chemically synthesized metallic nanowires but not others. A model that accounts for this well-known observation is presented. The model considers the influence of twin boundary energy and surface energy on nanowire growth kinetics, and it was tested using high-resolution electron microscopy and parallel-nanobeam diffraction data from geometrically identical nanowires of gold and platinum. The effects of twin boundary energy on nanowire growth kinetics can explain the structural difference between the gold and platinum nanowires without the need to speculate about the nature of ligand interactions during growth. [ABSTRACT FROM AUTHOR]

Abstract: Pt-nanowire (Pt-NW) catalyst layers were prepared by in-situ growing Pt nanowires onto carbon matrix coated on electrolyte membrane surface and used as PEMFC cathodes. The performances of the catalyst layer with various catalyst loadings and carbon matrix thicknesses were evaluated. Scanning electron microscopy (SEM) was employed to observe the morphology and thickness of the Pt-NW catalyst layers, energy-dispersive X-ray spectroscopy (EDS) was used to investigate the Pt distribution along the layers. The polarization curve, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) were performed in fuel cells to check the practical electrochemical activity of the Pt-NW catalyst layers. The results showed that the electrochemical surface area (ECSA) and the cell performance exhibited a volcano-type curve with different Pt loadings, while the carbon matrix thickness had an influence on the Pt-NW gradient distribution, the mass diffusion, and the charge transfer in the electrodes. [Copyright &y& Elsevier]

Abstract: The effects of ionomer contents were investigated in composite electrodes with in-situ grown single crystal Pt nanowires (Pt-NWs) for PEMFCs, including the amount in the carbon matrix and impregnated on the surface of the electrocatalyst layer. The electrocatalyst layer was prepared by growing Pt-NWs directly on the carbon matrix with a simple one-step wet chemical approach at room temperature. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), polarization curve tests, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) were employed to evaluate the ionomer effects. The experimental results showed that the ionomer in the carbon matrix had an influence on the ionic conductivity and aggregation and distribution of the Pt-NWs, and the ionomer impregnated on the surface of the electrocatalyst layer affected the mass transport and ionic conductivity. The performance of the MEA was improved by optimizing the ionomer contents. [Copyright &y& Elsevier]

Abstract: A strategy of sacrificial template was put forward to prepare porous Pt nanowires core with carbon shell (Pt PNW@C) using Te nanowires as template. These Pt PNW@C hybrids show a highly sensitive response to H2O2 oxidation recorded by chronoamperometry at 0.2V vs. the saturated calomel electrode (SCE). Under optimal conditions, this H2O2 transducer displays a linear range of 0.01–1.2μM with a sensitive of 6.28μAμM−1 cm−2 (r =0.9997), and a detection limit of 0.002μM (signal/noise=3). Moreover, the carbon layer on Pt PNW@C hybrids can greatly enhance the selectivity in H2O2 detection in the presence of the common interfering species, such as lactic acid (LA), uric acid (UA), creatinine and glucose, at a positive potential by compared with porous Pt nanowires (Pt PNWs). A glucose biosensor was constructed using this sensitive and selective H2O2 transducer combined with glucose oxidase. A calibration curve of glucose concentration can be obtained by measureing enzymatically generated H2O2, which shows a linear range from 0.5 to 20μM with a sensitivity of 0.35μAμM−1 cm−2 and a detection limit of 0.1μM. [Copyright &y& Elsevier]

The large-scale practical application of proton exchange membrane fuel cells (PEMFCs) is difficult to achieve if their performance and durability cannot be improved. We successfully synthesized N-doped carbon nanotube (NCNT) supported Pt nanowire catalysts (PtNW/NCNTs) using the soft template method with NCNTs as support. The results of transmission electron microscopy show that the Pt nanowires are uniformly loaded on the support (NCNTs). X-ray photoelectron spectroscopy reveals that the N atom doped on the surface is in the form of graphite N and pyridine N. The electrocatalytic activity of PtNW/NCNTs is studied via the half-cell electrochemistry test. The PtNW/NCNTs show better oxygen reduction reaction activity than commercial Pt/C catalysts. The results of the single-cell polarization experiment reveal that the performance of PEMFCs with PtNW/NCNTs is improved, and the maximum power density is 966 mW cm−2. After 500 h dynamic cycle durability test, the average voltage loss of the single cell is 3.6% for the PtNW/NCNTs catalyst and 7.2% for the Pt/C catalyst. The Pt/C catalyst demonstrates severe Pt nanoparticle growth and aggregation with a broad size distribution, the PtNW along with minimal changes observed. PtNW/NCNTs are a promising replacement to traditional Pt/C catalysts as electrocatalyst in PEMFC applications. [Display omitted] • PtNW/NCNTs were synthesized using the soft template method with NCNTs as support. •The ORR activity of the PtNW/NCNTs catalyst were remarkably improved. •The PtNW has reduced the mass transfer resistance values. •The PtNW/NCNTs catalyst has better performance and life of single cell. [ABSTRACT FROM AUTHOR]

A tremendous development of nanotechnology enabled us to prepare precisely structure-controlled nanocrystals (NCs). Recently, such structure controlled NCs have been applied as model catalysts with controlled active sites to evaluate reaction mechanisms. Here, we review our recent works on preparation of shape controlled Pt NCs, such as cube and wire, and on application as model catalysts for olefin hydrogenation to assess active Pt sites. A hydrogen reduction method of Pt(II) ion was adopted in an aqueous phase to prepare Pt cube in the presence of shape forming agent (NaI) and organic protective agent (sodium polyacrylate or sodium succinate). We succeed to prepare Pt cube with high size and shape selectivity, followed by very small Pt cube of less than 3 nm. Such simultaneous control of both size and shape of Pt NCs has been successfully achieved by the sophisticated tuning of multiple conditions for the growth kinetics of Pt nuclei during hydrogen reduction of PtCl in aq. N- , N-dimethylformamide (DMF) solution. The key strategy is to produce small Pt nuclei and to avoid the excessive growth of Pt nuclei, in conjunction with face selective adsorption of anionic protective and shape-forming agents by the control of solvent system. For the preparation of Pt nanowires with high anisotropy, template-assisted methods have been usually used. We have developed facile liquid phase preparation method at room temperature in air without any template. The key factors of the method are: firstly, to use aqueous organic solvent system to control solvent polarity; secondly, to use co-solvent DMF as shape forming agent; thirdly, to use excess NaBH as a stabilizer of Pt nuclei to prevent formation of conventional particles. Single-crystalline Pt nanowires of 2 nm diameter and more than micron length were easily obtained by the reduction of Pt(IV) with excess NaBH in water-DMF-toluene solution (1:8:5 volume ratio) in a short reaction period of 3 h. Then, we have applied shape-controlled Pt NCs protected with PAA prepared by our original methods, such as cube, tetrahedron and wire, as model catalysts for olefin ( cis- and trans-stilbenes) hydrogenation in ethanol to evaluate the active facet of Pt catalysts; e.g., Pt(111) or Pt(100). The estimated TOF values for the hydrogenation of cis- and trans-stilbene decreased in the order: cube > cuboctahedron > tetrahedron ~ nanowire. This tendency indicates that Pt(100) show high activity compared with Pt(111). The result is compatible with measurement of XPS and Raman spectra, suggesting strong adsorption of reactant on Pt(100). Hydrogenation of olefins (1-hexene and cyclohexene) has been carried out over Pt cubes with different sizes (8.2-10.1 nm) as catalysts to get information about active sites of Pt catalysts, e.g., flat facet or edge/corner atoms. The results of similar TOF values among Pt cubes with different sizes imply that the active sites are flat facets. [ABSTRACT FROM AUTHOR]

Abstract: The effect of varying Nafion® ionomer loadings coated on the surface of gas diffusion electrodes (GDEs) with in-situ grown single crystal Pt nanowires and their durability in Proton Exchange Membrane Fuel Cells (PEMFCs) were investigated. GDEs were fabricated by growing Pt nanowires directly onto the Gas Diffusion Layer (GDL) surface with a simple one-step wet chemical approach at room temperature, as reported in our previous studies. The samples were then coated with various Nafion® ionomer loadings and tested as cathodes in a 25 cm2 PEMFC hardware with Hydrogen/Air. The data were compared to commercial GDEs (E-TEK ELAT® GDE LT 120E-W). Performance results showed that the as-prepared GDEs with Pt nanowires required higher Nafion® ionomer loading coating compared to the commercial ones. Accelerated ageing tests (500 cycles of voltage scan) were performed in views of evaluating the as-prepared GDE durability. The experimental data showed that the as-prepared GDEs exhibited much larger current densities at 0.7 V but higher degradation rates compared to commercial GDEs, indicating that the as-prepared GDEs gave poor durability. This was due to the difference in GDE surface nanostructures influenced by the electrolyte ionomer loading coating. This effect is further discussed in this paper. [Copyright &y& Elsevier]

Abstract: Pt nanowires are prepared by treating electrospun polyvinyl pyrrolidone (PVP)–Pt composite fibers at high temperatures in an air atmosphere and their activities toward a methanol oxidation reaction (MOR) are investigated. Thermogravimetric analysis (TGA) and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) results indicate that the electrospun PVP–Pt composite fibers thermally decompose at 250°C, which leads to the removal of 98wt% of the PVP polymer and the simultaneous reduction of the Pt precursor to a Pt nanowire. The physical and electrochemical properties of Pt nanowires are found to be affected by the heat treatment conditions such as heating rate, time, temperature, and atmosphere. Furthermore, polymer fibers subjected to a pyrolization process in nitrogen followed by exposure to an air atmosphere enhance the surface area of the Pt nanowires, leading to high electrochemical activity toward a MOR. The detailed physical and electrochemical properties of the Pt nanowires are characterized by various spectroscopic and electrochemical techniques, and the possibilities of using them as electrocatalysts in a fuel cell are explored. [Copyright &y& Elsevier]

• Facile synthesis of Pt nanowires (PtNW) on carbon nanotubes (SWNT) introduced. • 100 times lower Pt content induces comparable activity to state of the art catalyst. • Activity attributed to metallic PtNW – SWNT interactions and morphology. • In an electrolyzer a stable voltage generated for more than 2000 h at a 1 A cm−2. Pertinent existing hydrogen technologies for energy storage require unsustainable amounts of scarce platinum group metals. Here, an electrocatalyst comprising high-aspect-ratio platinum nanowires (PtNWs) on single-walled carbon nanotubes (SWNTs) with ultralow Pt content (340 ng Pt cm−2) is employed for hydrogen evolution reaction (HER). A comparable activity (10 mA cm−2 at −18 mV vs. RHE) to that of state-of-the-art Pt/C (38,000 ng Pt cm−2) is reached in acidic aqueous electrolyte. This is attributed to favorable PtNW interaction with SWNTs and PtNW edge-sites which adsorb hydrogen optimally and aid at alleviating repulsive interactions. Moreover, the metallic nature of Pt, morphological effects and enhanced wetting contribute positively. The PtNW/SWNT relevance is emphasized at a proton-exchange-membrane electrolyzer generating stable voltage for more than 2000 h, successfully competing with the state-of-the-art reference but with one tenth of Pt mass loading. Overall, this work presents an unprecedently efficient HER catalyst and opens up avenues for PtNW/SWNT catalyzing other high-impact reactions. [ABSTRACT FROM AUTHOR]