Electrocatalytic properties of Pt nanowires supported on Pt and W gauzes

Wire-like Pt on mesoporous Ti0.7W0.3O2 Nanomaterial with Compelling Electro-Activity for Effective Alcohol Electro-Oxidation

Finding out robust active and sustainable catalyst towards alcohol electro-oxidation reaction is major challenges for large-scale commercialization of direct alcohol fuel cells. Herein, a robust Pt nanowires (NWs)/Ti_0.7W_0.3O₂ electrocatalyst, as the coherency of using non-carbon catalyst support and controlling the morphology and structure of the Pt nanocatalyst, was fabricated via an effortless chemical reduction reaction approach at room temperature without using surfactant/stabilizers or template to assemble an anodic electrocatalyst towards methanol electro-oxidation reaction (MOR) and ethanol electro-oxidation reaction (EOR). These observational results demonstrated that the Pt NWs/Ti_0.7W_0.3O₂ electrocatalyst is an intriguing anodic electrocatalyst, which can alter the state-of-the-art Pt NPs/C catalyst. Compared with the conventional Pt NPs/C electrocatalyst, the Pt NWs/Ti_0.7W_0.3O₂ electrocatalyst exhibited the lower onset potential (~0.1 V for MOR and ~0.2 for EOR), higher mass activity (~355.29 mA/mg_Pt for MOR and ~325.01 mA/mg_Pt for EOR) and much greater durability. The outperformance of the Pt NWs/Ti_0.7W_0.3O₂ electrocatalyst is ascribable to the merits of the anisotropic one-dimensional Pt nanostructure and the mesoporous Ti_0.7W_0.3O₂ support along with the synergistic effects between the Ti_0.7W_0.3O₂ support and the Pt nanocatalyst. Furthermore, this approach may provide a promising catalytic platform for fuel cell technology and a variety of applications.

Preparation and Characterization of Advanced PtRu/Ti0.7Mo0.7O2 Catalysts for Direct Methanol Fuel Cells

We report the new strategy by investigating the novel Ti0.7Mo0.3O2material can just as easily be used as a conductive support for PtRu for DMFCs to prevent not only the carbon corrosion but also improved activity of catalyst due to some functional advantages of novel Ti0.7Mo0.3O2support. The Ti0.7Mo0.3O2nanoparticle have good crystallinity with well-defined fringes corresponding to the 3.45 Å spacing value of the {101} plane of anatase TiO2, which were good according to the XRD pattern. The BET surface area measurements showed that the Ti0.7Mo0.3O2possessed 125 m2g-1Fig. 3 shows the TEM measurement of Ti0.7Mo0.3O2nanoparticle and Pt/Ti0.7Mo0.3O2, it can be observed that spherical PtRu alloy particles with an average particle size of 2-4 nm were uniformly anchored on the surface of Ti0.7Mo0.3O2support. More importantly, we found that there has a strong metal support interaction (SMSI) between the PtRu noble metal and the Ti0.7Mo0.3O2support material - resulting in facile electron donation from the Ti0.7Mo0.3O2support to PtRu metal with an ultimate drastic decrease in the d-band vacancy of Pt. Thus, the unique structural features of the Ti0.7Mo0.3O2support and the PtRu/Ti0.7Mo0.3O2catalyst appear to provide a suitable combination favoring that promise for the high performance of methanol oxidation, CO-tolerance in DMFCs.

Electroreduction of carbon dioxide to formate over a thin-layered tin diselenide electrode

We first report a thin-layered SnSe₂ film as a robust catalyst for CO₂ electroreduction, efficiently affording formate with a faradaic efficiency of 91% and a stable activity for more than 100 h at −0.8 V versus the reversible hydrogen electrode.

Tuning Nanowires and Nanotubes for Efficient Fuel-Cell Electrocatalysis

Developing new synthetic methods for the controlled synthesis of Pt-based or non-Pt nanocatalysts with low or no Pt loading to facilitate sluggish cathodic oxygen reduction reaction (ORR) and organics oxidation reactions is the key in the development of fuel-cell technology. Various nanoparticles (NPs), with a range of size, shape, composition, and structure, have shown good potential to catalyze the sluggish cathodic and anodic reactions. In contrast to NPs, one-dimensional (1D) nanomaterials such as nanowires (NWs), and nanotubes (NTs), exhibit additional advantages associated with their anisotropy, unique structure, and surface properties. The prominent characteristics of NWs and NTs include fewer lattice boundaries, a lower number of surface defect sites, and easier electron and mass transport for better electrocatalytic activity and lower vulnerability to dissolution, Ostwald ripening, and aggregation than Pt NPs for enhanced stability. An overview of recent advances in tuning 1D nanostructured Pt-based, Pd-based, or 1D metal-free nanomaterials as advanced electrocatalysts is provided here, for boosting fuel-cell reactions with high activity and stability, including the oxygen reduction reaction (ORR), methanol oxidation reaction (MOR), and ethanol oxidation reaction (EOR). After highlighting the different strategies developed so far for the synthesis of Pt-based 1D nanomaterials with controlled size, shape, and composition, special emphasis is placed on the rational design of diverse NWs and NTs catalysts such as Pt-based NWs or NTs, non-Pt NTs, and carbon NTs with molecular engineering, etc. for enhancing the ORR, MOR, and EOR. Finally, some perspectives are highlighted on the development of more efficient fuel-cell electrocatalysts featuring high stability, low cost, and enhanced performance, which are the key factors in accelerating the commercialization of fuel-cell technology.

Small-sized and highly dispersed Pt nanoparticles loading on graphite nanoplatelets as an effective catalyst for methanol oxidation

A series of high loading Pt nanoparticles (NPs) with a small particle size uniformly dispersed on graphite nanoplatelets (GNPs) have been synthesized in the presence of an imidazolium-based ionic liquid (Pt/I-IL (x)/GNPs). I-IL, an amphoteric ion used as an additive agent to stabilize Pt NPs, can also prevent the aggregation of the GNPs. The results obtained from X-ray diffraction, transmission electron microscopy and electrochemical testing showed that the I-IL assisted synthesis method resulted in size reduction of Pt NPs, an improvement of Pt dispersion on GNPs, and the identification of the relationships between the mean size of Pt NPs and the volume of I-IL. Among all as-prepared Pt/GNP catalysts with or without I-IL assisted, the sample with 10 microliters of I-IL assisted (Pt/I-IL (10)/GNPs) exhibits the highest electrocatalytic activity and the best stability toward the methanol oxidation reaction. Moreover, the Pt/I-IL (10)/GNP catalyst markedly outperforms the commercial Pt/C from Johnson Matthey in terms of both methanol oxidation activity and stability, revealed by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy.

Microemulsion-controlled synthesis of one-dimensional Ir nanowires and their catalytic activity in selective hydrogenation of o-chloronitrobenzene

Ultrathin iridium nanowires have been synthesized using a convenient method mediated by microemulsion via oriented attachment growth for the first time. The interconnected polycrystalline Ir nanowires possess high aspect ratio, small average diameter of 2 nm, and length up to several hundred nanometers. The 1D growth of surfactant-encapsulated primary nanoparticles, which is determined by the inherent crystal growth habit and the specific interactions of nanocrystals with surfactant molecules, accounts for the formation of Ir nanowires. The as-prepared Ir nanowires show high activity and selectivity toward the hydrogenation production of industrially valuable chloroaniline from o-chloronitrobenzene. Theoretical evidence based on DFT calculation indicates that H2 could be dissociated more easily and quickly on Ir(100) surface than on Ir(111), accounting for the higher hydrogenation rate over Ir nanowires exposing both (200) and (111) crystal facets rather than only (111) facet for Ir nanoparticles.

Plasma nitriding induced growth of Pt-nanowire arrays as high performance electrocatalysts for fuel cells

In this work, we demonstrate an innovative approach, combing a novel active screen plasma (ASP) technique with green chemical synthesis, for a direct fabrication of uniform Pt nanowire arrays on large-area supports. The ASP treatment enables in-situ N-doping and surface modification to the support surface, significantly promoting the uniform growth of tiny Pt nuclei which directs the growth of ultrathin single-crystal Pt nanowire (2.5–3 nm in diameter) arrays, forming a three-dimensional (3D) nano-architecture. Pt nanowire arrays in-situ grown on the large-area gas diffusion layer (GDL) (5 cm²) can be directly used as the catalyst electrode in fuel cells. The unique design brings in an extremely thin electrocatalyst layer, facilitating the charge transfer and mass transfer properties, leading to over two times higher power density than the conventional Pt nanoparticle catalyst electrode in real fuel cell environment. Due to the similar challenges faced with other nanostructures and the high availability of ASP for other material surfaces, this work will provide valuable insights and guidance towards the development of other new nano-architectures for various practical applications.

Nitrogen self-doped porous carbon from surplus sludge as metal-free electrocatalysts for oxygen reduction reactions

Nitrogen self-doped porous carbon was prepared by calcination treatment of surplus sludge, a toxic byproduct from microbial wastewater treatments, and exhibited a mesoporous structure, as manifested in scanning and transmission electron microscopic measurements. Nitrogen adsorption/desorption studies showed that the porous carbon featured a BET surface area as high as 310.8 m(2)/g and a rather broad range of pore size from 5 to 80 nm. X-ray photoelectron spectroscopic studies confirmed the incorporation of nitrogen into the graphitic matrix forming pyridinic and pyrrolic moieties. Interestingly, the obtained porous carbon exhibited apparent electrocatalytic activity in oxygen reduction in alkaline media, with the optimal temperatures identified within the range of 600 to 800 °C, where the number of electron transfers involved in oxygen reduction was estimated to be 3.5 to 3.7 and the performance was rather comparable to leading literature results as a consequence of deliberate engineering of the graphitic matrix by nitrogen doping.

Cost-effective atomic layer deposition synthesis of Pt nanotube arrays: application for high performance supercapacitor

Due to the unique advantages of Pt, it plays an important role in fuel cells and microelectronics. Considering the fact that Pt is an expensive metal, a major challenging point nowadays is how to realize efficient utilization of Pt. In this paper, a cost-effective atomic layer deposition (ALD) process with a low N2 filling step is introduced for realizing well-defined Pt nanotube arrays in anodic alumina nano-porous templates. Compared to the conventional ALD growth of Pt, much fewer ALD cycles and a shorter precursor pulsing time are required, which originates from the low N2 filling step. To achieve similar Pt nanotubes, about half cycles and 10% Pt precursor pulsing time is needed using our ALD process. Meanwhile, the Pt nanotube array is explored as a current collector for supercapacitors based on core/shell Pt/MnO2 nanotubes. This nanotube-based electrode exhibits high gravimetric and areal specific capacitance (810 Fg(-1) and 75 mF cm(-2) at a scan rate of 5 mV s(-1) ) as well as an excellent rate capability (68% capacitance retention from 2 to 100 Ag(-1) ). Additionally, a negligible capacitance loss is observed after 8000 cycles of random charging-discharging from 2 to 100 Ag(-1) .

One-pot synthesis of ultralong coaxial Au@Pt nanocables with numerous highly catalytically active perpendicular twinning boundaries and Au@Pt core-shell bead structures

Ultralong coaxial Au@Pt nanocables prepared by one-pot synthesis exhibit excellent electrocatalytic activity due to structural features of (1) numerous twinning boundaries and (2) lattice mismatch between the core and the shell.

Solution epitaxial growth of cobalt nanowires on crystalline substrates for data storage densities beyond 1 Tbit/in2

The implementation of nano-objects in numerous emerging applications often demands their integration in macroscopic devices. Here we present the bottom-up epitaxial solution growth of high-density arrays of vertical 5 nm diameter single-crystalline metallic cobalt nanowires on wafer-scale crystalline metal surfaces. The nanowires form regular hexagonal arrays on unpatterned metallic films. These hybrid heterostructures present an important perpendicular magnetic anisotropy and pave the way to a high density magnetic recording device, with capacities above 10 Terabits/in(2). This method bypasses the need of assembling and orientating free colloidal nanocrystals on surfaces. Its generalization to other materials opens new perspectives toward many applications.

Magnetically recoverable nanoflake-shaped iron oxide/Pt heterogeneous catalysts and their excellent catalytic performance in the hydrogenation reaction

In this study, a kind of unique Fe2O3/Pt hybrid consisting of uniform platinum nanoparticles deposited on a nanoflake-shaped Fe2O3 support was prepared by using a solvothermal reaction followed by a heat-induced reduction process. The prepared Fe2O3 sample displays well-defined nanoflake-like morphology; remarkably, there are many specific cavities on its surface. In addition, uniform Pt nanoparticles with narrow size distribution were deposited onto the surface of the preformed flake-like Fe2O3 support to form the Fe2O3/Pt hybrid via a facile heat-induced reduction reaction. Thus, the prepared Fe2O3/Pt hybrid can serve as heterogeneous catalyst over the hydrogenation reaction. Results demonstrated that the specific Fe2O3/Pt heterogeneous catalyst exhibits good catalytic performances, including high conversion, specific selectivity, and excellent recycling durability, over hydrogenation reactions for different substrates. Furthermore, the prepared Fe2O3/Pt heterogeneous catalyst could be easily separated from the product mixture by using a magnet and could be recycled for 10 cycles without catalytic activity loss. In a word, the present synthetic approach is facile, scalable, and reproducible, which can be easily facilitated to prepare other types of noble metals/metal oxide composite systems.

Twinning boundary-elongated hierarchical Pt dendrites with an axially twinned nanorod core for excellent catalytic activity

Introduction of twinning boundary elongation and lattice mismatch to the hierarchical and dendritic Pt₃Ni@Pt nanostructures by heteroepitaxial twinning transfer from five-fold twinned Pt₃Ni nanorods leads to great enhancement of the electrocatalytic performance in MOR and ORR.

A facile approach for in situ synthesis of graphene-branched-Pt hybrid nanostructures with excellent electrochemical performance

A facile and green approach for the synthesis of highly electroactive branched Pt nanostructures well dispersed on graphene has been developed by in situ reduction of graphene oxides and Pt(iv) ions in an aqueous medium. The as-synthesized branched Pt and graphene hybrid nanomaterials (GR-BPtNs) were thoroughly characterized using Transmission Electron Microscope (TEM), UV-Visible spectroscopy, Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and Raman spectroscopy. This report clearly exploits the decisive role of the graphene support, the pH of the solution and the stabiliser on shaping the branched morphology of the Pt nanostructures well dispersed on graphene. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy (EIS) measurements were employed to investigate the electrocatalytic performance and durability of GR-BPtNs towards methanol oxidation and oxygen reduction. The results reveal that the synergetic effect of the graphene support and the branched morphology triggers electrocatalytic performance and robust tolerance to surface poisoning of GR-BPtNs.

Self-supported Pt nanoclusters via galvanic replacement from Cu2O nanocubes as efficient electrocatalysts

A novel synthesis method for self-supported Pt nanoclusters (Pt NCs) comprised of interconnected 2-3 nm Pt nanoparticles was developed by employing the galvanic replacement process between Cu2O nanocubes and PtCl4(2-) ions. This discovered synthesis procedure eliminates the use of any polymer capping agents and enables a catalytically clean Pt surface. It is determined that the presence of H(+) ions is crucial for initializing the galvanic replacement reaction. The electrocatalytic performances of the Pt NCs were tested for both oxygen reduction and methanol oxidation reactions, which showed higher electrochemical activity and greater long-term durability as compared with commercial Pt materials.

Growth of Pt nanowires by atomic layer deposition on highly ordered pyrolytic graphite

The formation of Pt nanowires (NWs) by atomic layer deposition on highly ordered pyrolytic graphite (HOPG) is investigated. Pt is deposited only at the step edges of HOPG and not on the basal planes, leading to the formation of laterally aligned Pt NWs. A growth model involving a morphological transition from 0-D to 1-D structures via coalescence is presented. The width of the NWs grows at a rate greater than twice the vertical growth rate. This asymmetry is ascribed to the wetting properties of Pt on HOPG as influenced by the formation of graphene oxide. A difference in Pt growth kinetics based on crystallographic orientation may also contribute.

Synthesis of octopus-tentacle-like Cu nanowire-Ag nanocrystals heterostructures and their enhanced electrocatalytic performance for oxygen reduction reaction

In this article, the novel octopus-tentacle-like Cu nanowire-Ag nanocrystals heterostructures have been fabricated in solution phase via heterogeneous nucleation and growth of Ag nanocrystals on presynthesized Cu nanowires. The growth environment and dynamic factors of Ag nanocrystals play an important role for formation of such heterostructures. Combined the physical constants of Cu and Ag with a series of control experiments, the epitaxial growth means of Ag nanocrystals on Cu nanowire is found to abide by "layer-plus-island" (Stranski-Krastanow) mode. Because of the presence of multiple junctions and strong synergistic effect of their constituents, the obtained heterostructures exhibit greatly enhanced electrocatalytic performance toward oxygen reduction reaction compared with that of pure Ag nanocrystals, Cu nanowires, and mechanically mixed dual components as well as recently reported some non-Pt materials, which can be served as an alternative cathodic electrocatalyst to apply in alkaline fuel cells. Moreover, our method can be extended to fabricate octopus-tentacle-like Cu nanowire-Au nanocrystals and Cu nanowire-Pd nanocrystals heterostructures.

Kinetic study of Pt nanocrystal deposition on Ag nanowires with clean surfaces via galvanic replacement

Without using any templates or surfactants, this study develops a high-yield process to prepare vertical Ag-Pt core-shell nanowires (NWs) by thermally assisted photoreduction of Ag NWs and successive galvanic replacement between Ag and Pt ions. The clean surface of Ag nanowires allows Pt ions to reduce and deposit on it and forms a compact sheath comprising Pt nanocrystals. The core-shell structural feature of the NWs thus produced has been demonstrated via transmission electron microscopy observation and Auger electron spectroscopy elemental analysis. Kinetic analysis suggests that the deposition of Pt is an interface-controlled reaction and is dominated by the oxidative dissolution of Ag atoms. The boundaries in between Pt nanocrystals may act as microchannels for the transport of Ag ions during galvanic replacement reactions.

Recent advances in electrochemical sensing for hydrogen peroxide: a review

Due to the significance of hydrogen peroxide (H(2)O(2)) in biological systems and its practical applications, the development of efficient electrochemical H(2)O(2) sensors holds a special attraction for researchers. Various materials such as Prussian blue (PB), heme proteins, carbon nanotubes (CNTs) and transition metals have been applied to the construction of H(2)O(2) sensors. In this article, the electrocatalytic H(2)O(2) determinations are mainly focused on because they can provide a superior sensing performance over non-electrocatalytic ones. The synergetic effect between nanotechnology and electrochemical H(2)O(2) determination is also highlighted in various aspects. In addition, some recent progress for in vivo H(2)O(2) measurements is also presented. Finally, the future prospects for more efficient H(2)O(2) sensing are discussed.

Highly-ordered supportless three-dimensional nanowire networks with tunable complexity and interwire connectivity for device integration

The fabrication of three-dimensional assemblies consisting of large quantities of nanowires is of great technological importance for various applications including (electro-)catalysis, sensitive sensing, and improvement of electronic devices. Because the spatial distribution of the nanostructured material can strongly influence the properties, architectural design is required in order to use assembled nanowires to their full potential. In addition, special effort has to be dedicated to the development of efficient methods that allow precise control over structural parameters of the nanoscale building blocks as a means of tuning their characteristics. This paper reports the direct synthesis of highly ordered large-area nanowire networks by a method based on hard templates using electrodeposition within nanochannels of ion track-etched polymer membranes. Control over the complexity of the networks and the dimensions of the integrated nanostructures are achieved by a modified template fabrication. The networks possess high surface area and excellent transport properties, turning them into a promising electrocatalyst material as demonstrated by cyclic voltammetry studies on platinum nanowire networks catalyzing methanol oxidation. Our method opens up a new general route for interconnecting nanowires to stable macroscopic network structures of very high integration level that allow easy handling of nanowires while maintaining their connectivity.