Activity Of Platinum Nanoparticles Research Articles

Microfluidically Produced Microcapsules with Amphiphilic Polymer Conetwork Shells

AbstractMicrocapsules with an aqueous core can be conveniently prepared by water‐in‐oil‐in‐water double emulsion microfluidics. However, conventional shell materials are based on hydrophobic polymers or colloidal particles. Thus, these microcapsules feature a hydrophobic shell impermeable to water‐soluble compounds. Capsules with semipermeable hydrogel shells have been demonstrated but may exhibit poor mechanical properties. Here, amphiphilic polymer conetworks (APCNs) based on poly(2‐hydroxyethyl acrylate)‐linked by‐polydimethylsiloxane (PHEA‐l‐PDMS) are introduced as a new class of wall materials in double emulsion microcapsules. These APCNs are mechanically robust silicone hydrogels that are swellable and permeable to water and are soft and elastic when dry or swollen. Therefore, the microcapsules can be dried and rehydrated multiple times or shrunken in sodium chloride salt solutions without getting damaged. Moreover, the APCNs are permeable for hydrophilic organic compounds and impermeable for macromolecules. Thus, they can be loaded with macromolecules or nanoparticles during microfluidic formation and with organic molecules after capsule synthesis. The microcapsules serve as microreactors for catalytically active platinum nanoparticles that decompose hydrogen peroxide. Finally, the surface of the APCN microcapsules can be selectively functionalized with a cholesterol‐based linker. Concluding, APCN microcapsules could find applications for the controlled delivery of drugs, as microreactors for synthesis, or as scaffolds for synthetic cells.

The Effect of Heteroatom-Doped Graphene Supports on the PtNPs Electrocatalytic Activity for ORR

There has been a global shift in energy production emphasizing the reduction of fossil fuels by the augmentation of more renewable energy. Proton-exchange membrane fuel cells (PEMFC) and anion-exchange membrane fuel cells (AEMFC) can mitigate a need for fossil fuels and provide an alternative route of hydrogen-based energy production. Fuel cells utilize a catalyst at both the cathode and anode to increase the overall kinetics of the redox reactions and enhance the cell performance.1 Current fuel cell technology employs a platinum based catalyst due to its efficiency and robust performance in both alkaline and acidic environments.1,2 The drawbacks associated with Pt-based catalysts are centered around its economic viability and its affinity towards surface poisoning.1 A catalyst using platinum nanoparticles (PtNPs) loaded onto a graphene support can address some of the aforementioned drawbacks.1 To maximize the electrocatalytic activity of the PtNPs – all aspects of the PtNPs catalyst must be optimized, which includes the optimization of the support material. The effect that the different commercially available heteroatom-doped graphene had on the activity of the PtNPs was investigated during this study. The PtNPs were synthesized using the citrate method, which produces ≤ 5 nm size particles. Our study confirmed that the choice of doped graphene support has an effect on the overall activity of PtNPs. The results were confirmed via a comparison with PtNPs supported on Vulcan XC-72R carbon. All Pt catalysts supported on the doped graphene showed an improvement in the oxygen reduction reaction (ORR) half-wave potentials (E 1/2) over PtNPs on Vulcan XC-72R carbon (Fig. 1A); with the nitrogen-doped graphene exhibiting the greatest improvements in the half-wave potential with the E 1/2 value of 0.85 V vs. RHE as compared to the 0.77 V of the Pt/C. A comparison of the Tafel slopes (Fig. 1B) confirmed that the transfer of the first electron was the rate-determining step for all of the Pt catalysts supported on doped graphene as all Tafel slopes were around -120 mV per decade. This has been confirmed in literature with Pt on various carbon supports.2 Figure 1. A) Comparison of RDE polarization curves for oxygen reduction on Pt/NGr (pink), Pt/SGr (green) and Pt/N-PGr (blue) with Pt/C (black) at 1900 rpm in a O2-saturated 0.1 M HClO4 solution (v= 10 mV s−1). B) Mass transfer corrected Tafel plots derived from A

Two Mesoporous Domains Are Better Than One for Catalytic Deconstruction of Polyolefins.

Catalytic hydrogenolysis of polyolefins into valuable liquid, oil, or wax-like hydrocarbon chains for second-life applications is typically accompanied by the hydrogen-wasting co-formation of low value volatiles, notably methane, that increase greenhouse gas emissions. Catalytic sites confined at the bottom of mesoporous wells, under conditions in which the pore exerts the greatest influence over the mechanism, are capable of producing less gases than unconfined sites. A new architecture was designed to emphasize this pore effect, with the active platinum nanoparticles embedded between linear, hexagonal mesoporous silica and gyroidal cubic MCM-48 silica (mSiO2/Pt/MCM-48). This catalyst deconstructs polyolefins selectively into ∼C20-C40 paraffins and cleaves C-C bonds at a rate (TOF = 4.2 ± 0.3 s-1) exceeding that of materials lacking these combined features while generating negligible volatile side products including methane. The time-independent product distribution is consistent with a processive mechanism for polymer deconstruction. In contrast to time- and polymer length-dependent products obtained from non-porous catalysts, mSiO2/Pt/MCM-48 yields a C28-centered Gaussian distribution of waxy hydrocarbons from polyolefins of varying molecular weight, composition, and physical properties, including low-density polyethylene, isotactic polypropylene, ultrahigh-molecular-weight polyethylene, and mixtures of multiple, post-industrial polyolefins. Coarse-grained simulation reveals that the porous-core architecture enables the paraffins to diffuse away from the active platinum site, preventing secondary reactions that produce gases.

Effect of tin content on TiO2-supported platinum-tin bimetallic catalysts for low temperature CO oxidation reaction

Removal of carbon monoxide (CO) is a significant issue in fuel processing for the production of hydrogen. Bimetallic platinum-tin catalysts are well-known as efficient catalysts for oxidation process due to their synergistic bi-functional mechanism, their ability to dissociate molecular oxygen at low temperature, and their capacity to adsorb both atomic oxygen and CO. In this study, we synthesized titanium dioxide supported platinum-tin bimetallic catalysts for low temperature CO oxidation process with different amount of tin. Titanium dioxide provided oxygen to active sites due to its abundant oxygen vacancies and prevented metal sintering of active platinum nanoparticles. We confirmed that our titanium dioxide supported platinum-tin bimetallic catalysts showed excellent performance for low temperature CO oxidation. Moreover, the amount of tin on titanium dioxide affected the adsorption behaviors of CO and O2, resulting in the difference in catalytic activity of Pt based catalysts.

Platinum Nanoparticles Uniformly Dispersed on Covalent Organic Framework Supports for Selective Synthesis of Secondary Amines

AbstractCovalent organic frameworks (COFs) with pore structures are talented supports for active components. In this report, COF has been rationally fabricated and served as host for growing uniformly dispersed platinum nanoparticles with a narrow size distribution (2 nm). The obtained hybrid Pt/COF exhibits high catalytic activity in the reductive amination of benzaldehyde towards secondary amines with a yield of 96 % and good recyclability. The preferable selectivity towards secondary amines could be attributed to synergistic effects of active platinum nanoparticles and COF, in which metallic Pt nanoparticles were uniformly dispersed with a positively charged surface. This work will open an avenue towards controlling the interaction between active metals and support as well as rational design of catalysts for demanding transformations for fine agrochemicals intermediates.

Enhancement of the Oxygen Reduction Reaction Activity of Pt by Tuning Its d-Band Center via Transition Metal Oxide Support Interactions

The enhancement of the oxygen reduction reaction (ORR) activity of platinum nanoparticles (Pt NPs) using transition metal oxide (MOx, M = Ti, Nb, Ta, W, Y, and Zr) supports has been examined. To enable the use of transition metal oxides having low electric conductivity as supports, Pt NPs were formed on thin transition metal oxides formed on conducting cup-stacked carbon nanotubes (CSCNTs). Metal oxide composites (M1M2Ox) prepared from two types of transition metal (M1M2: TiNb, NbTa, and TaW) precursors were also used as supports. Pt NPs were photodeposited on MOx/CSCNTs and M1M2Ox/CSCNT supports, resulting in MOx/CSCNT- and M1M2Ox/CSCNT-supported Pt NP catalysts (abbreviated as Pt/MOx/CSCNTs and Pt/M1M2Ox/CSCNTs). Their ORR activities in 0.1 M HClO4 aqueous solution were found to significantly depend on the atomic ratio of M1 and M2 in M1M2Ox and the type of metal oxide support. A “volcano-type” dependence of the ORR activity (represented as the current density, mass activity, and specific activity at 0.9 V vs reversible hydrogen electrode (RHE)) on the Pt d-band center, relative to the Fermi level, was obtained in a series of the Pt/MOx/CSCNTs and Pt/M1M2Ox/CSCNT catalysts. It was found that the d-band center values (ranging from −3.83 to −3.42 eV) of Pt deposited on MOx/CSCNTs and M1M2Ox/CSCNT supports were lower than that (−3.39 eV) of the reference Pt/carbon black (CB) and that the Pt/TiNbOx (Ti/Nb = 1:6.6 in atomic ratio)/CSCNTs with a d-band center of −3.59 eV exhibited the maximum ORR activity, in agreement with the theoretical expectation that an ORR catalyst having a d-band center that is ca. 0.2 eV lower than that of Pt would have maximal ORR activity.

Stability and activity of platinum nanoparticles in the oxygen electroreduction reaction: is size or uniformity of primary importance?

Platinum–carbon catalysts are widely used in the manufacturing of proton-exchange membrane fuel cells. Increasing Pt/C activity and stability is an urgent task and the optimization of their structure seems to be one of the possible solutions. In the present paper, Pt/C electrocatalysts containing small (2–2.6 nm) nanoparticles (NPs) of a similar size, uniformly distributed over the surface of a carbon support, were obtained by the original method of liquid-phase synthesis. A comparative study of the structural characteristics, catalytic activity in the oxygen electroreduction reaction (ORR), and durability of the synthesized catalysts, as well as their commercial analogs, was carried out. It was shown that the uniformity of the structural and morphological characteristics of Pt/C catalysts makes it possible to reduce the negative effect of the small size of NPs on their stability. As a result, the obtained catalysts were significantly superior to their commercial analogs regarding ORR activity, but not inferior to them in terms of stability.

Enhancement of Oxygen Reduction Reaction Activity of Pt By Tuning Its D-band Center Via Transition Metal Oxide Support Interactions

The enhancement of the oxygen reduction reaction (ORR) activity of platinum nanoparticles (Pt NPs) using transition metal oxide (MOx, M = Ti, Nb, Ta, W, Y and Zr) supports has been examined. In order to enable the use of transition metal oxides having low electric conductivity as supports, the Pt nanoparticles were formed on conducting cup-stacked carbon nanotubes (CSCNTs). Metal oxide composites (M1M2Ox) prepared from two types of transition metal (M1M2: TiNb, NbTa and TaW) precursors were also used as supports. Pt NPs were photodeposited on MOx/CSCNTs and M1M2Ox/CSCNTs supports, resulting in MOx/CSCNTs and M1M2Ox/CSCNTs-supported Pt NPs catalysts (abbreviated as Pt/MOx/CSCNTs and Pt/M1M2Ox/CSCNTs). Their ORR activities in 0.1 M HClO4 aqueous solution were found to significantly depend on the atomic ratio of M1 and M2 in M1M2Ox as well as the type of metal oxide support. A “volcano-type” dependence of the ORR activity (represented as current density, mass activity and specific activity at 0.9 V vs. RHE) on the Pt d-band center, relative to the Fermi level, was obtained in a series of the Pt/MOx/CSCNTs and Pt/M1M2Ox/CSCNTs catalysts. It was found that the d-band center values (ranging from -3.83 to -3.42 eV) of the Pt deposited on MOx/CSCNTs and M1M2Ox/CSCNTs supports were lower than that (-3.39 eV) of the reference Pt/carbon black (CB), and that the Pt/TiNbOx (Ti:Nb = 1:6.6 in atomic ratio)/CSCNTs with a d-band center of -3.59 eV exhibited the maximum ORR activity, in agreement with the theoretical expectation that an ORR catalyst having a d-band center which is ca. 0.2 eV lower than that of Pt would have maximal ORR activity. A possible contribution of lattice strain (geometric effect) to the enhanced ORR activity is also briefly discussed. Our results demonstrate that the ORR activity of Pt NPs deposited on a series of the metal oxide supports can be deliberately controlled by the choice of support and CSCNTs.

A nanocomposite hydrogel with catalytic properties for trace-element detection in real-world samples

A nanocomposite material characterized by peroxidase-like properties was developed through the dispersion of platinum nanoparticles (PtNPs) inside a hydrogelic matrix. The integration of the PtNP catalysts within the matrix resulted in their stabilization, preventing aggregation and precipitation in media of environmental interest, characterized by high ionic strength and by the presence of organic solutes. A thorough optimization of the matrix design was aimed at granting optimal diffusion of the reagents, in order to maintain the efficiency of the catalytic action. Such combined features allowed the implementation and prototyping of a colorimetric method for the detection of mercury in environmental water samples. The assay was based on a chromogenic reaction catalyzed by the peroxidase-like activity of PtNPs and its specific inhibition caused by trace amounts of mercury.

Synthesis, characterization of platinum(II) complexes of Schiff base ligands and evaluation of cytotoxic activity of platinum nanoparticles

New cytotoxic mononuclear Pt(II) coordination complexes of ligands {hydrazinecarboxamide (L1H) and hydrazinecarbothioamide (L2H) of 2-hydroxy-1-naphthaldehyde} have been synthesized. Free ligands, their metal complexes, and metal nanoparticles have been characterized based on elemental analysis, melting point, and molecular weight determinations, magnetic measurements, SEM, IR, 1H NMR, and UV–Visible spectra. Square planar geometry has been proposed to the complexes. The ligands and their complexes exhibit antimicrobial effects against various strains of bacteria and fungi. Platinum(II) nanoparticles were prepared by using green technique. The gel electrophoresis clearly exhibits that the metal complexes along with the ligands show cleavage activity on DNA of Escherichia coli (ATCC 25922). The newly synthesized complexes manifested significant in vitro cytotoxicity against human MCF-7 breast adenocarcinoma cancer cell line with cell death mainly caused by apoptosis. Further, nanoparticles of Pt complex exhibited MCF-7 cell multiplication through induction of apoptotic cell death.

Cellulose nanocrystal/clay based macroion nanogel as support for stable platinum catalyst for electrochemical oxidation of methanol in alkaline medium

Nanogels are well known for their ability to encapsulate metal nanoparticles. However, only few reports exist on the application of such metal nanoparticle-loaded nanogels as electrocatalyst. Here, the formation of a self-assembled macroion nanogel-based complex using sustainable nanomaterials and its functional application as catalyst support for methanol oxidation in alkaline medium is reported. Physico-chemical and morphological investigations of the nanogel showed the formation of micro-nano particles, suggesting the presence of good ionic interactions. Prepared complex was utilized to host catalytically active platinum nanoparticles. On calcination, Pt-loaded nanogels showed good activity towards methanol oxidation in alkaline medium. Further, based on linear sweep voltammetry, it was proposed that for the current system reported here, reaction intermediates formed in methanol oxidation during the cyclic voltammetry analysis get removed from the catalyst surface during the forward scan, instead of the reverse scan. The proposed hypothesis was further supported by impedance analysis and the potential range for removal of intermediates was determined, which was found to be 0.1 V – 0.2 V in alkaline medium during the forward scan. Thus, it has been successfully demonstrated that such catalytic nanoparticle-encapsulated complexes have good electrochemical activity.

Active Platinum Nanoparticles as a Bifunctional Promoter for Lithium−Sulfur Batteries

AbstractAs a widely used electrocatalyst in fuel cells, metallic platinum has achieved great success in terms of kinetic promotion. Still plagued by a familiar problem, owing to the sluggish kinetics of irreversible Li2S2/Li2S species deposition, lithium−sulfur batteries with high theoretical energy are far from being realized. Inspired by the similarity between oxygen and sulfur, being in the same group, commercially available Pt/C was investigated here to explore the possible effect on the sulfur cathode. The electrochemical tests show that the electrode with 2 wt% Pt added delivers a 61 % enhancement in the discharging specific capacity compared to the control electrode after 200 cycles at 0.5 C, along with an average coulombic efficiency of 98.3 %. It is proven that these beneficial results can be attributed to the favorable capability of polysulfide immobilization and effective inhibition of self‐discharging behavior. The ex situ XPS analysis and the increased exchange current density further reveal that the involved platinum nanoparticles could not only function as a static chemical absorber for polysulfide species, but, more importantly, to promote the redox kinetic effectively as an electrochemical catalyst. The positive effect of utilizing commercial Pt/C materials directly on sulfur cathodes is of great significance in developing sulfur cathodes for Li/S batteries.

Highly active platinum nanoparticles supported by nitrogen/sulfur functionalized graphene composite for ethanol electro-oxidation

In this study, Pt nanoparticles are deposited on the surface of nitrogen-sulfur functionalized reduced graphene oxide and mixed with double wall carbon nanotubes (Pt/NS-rGO/DWCNT). The obtained nanocomposite is used as an electrocatalyst for the ethanol electro-oxidation reaction (EOR). CO oxidation studies with differential electrochemical mass spectroscopy (DEMS) show a lower onset potential indicating higher poisoning tolerance of these materials. The electrocatalytic activity of the Pt/NS-rGO/DWCNT nanocomposite is studied at different temperatures (40, 50, 60, and 70°C) and compared with that of Pt/rGO, Pt/rGO/DWCNT composites and commercial carbon-supported Pt catalyst. Pt/rGO/DWCNT and Pt/NS-rGO/DWCNT display significantly higher ethanol electro-oxidation currents especially at low potentials relevant to fuel cell applications. At high temperatures (>50°C), Pt/NS-rGO/DWCNT is the most active catalyst in concordance with its higher apparent activation energy. Pt/NS-rGO/DWCNT is also the most durable of the catalysts after a 500 potential cycle test and suffers the least from poisoning effects during chronopotentiometric testing. These results allow to conclude that combining NS-functionalized graphene catalyst support with DWCNT to form a composite provides excellent performances due to enhanced Pt electrocatalytic activity from NS-functionalization and enhanced mass transfer from the DWCNT filler.

High-Utilisation Nanoplatinum Catalyst (Pt@cPIM) Obtained via Vacuum Carbonisation in a Molecularly Rigid Polymer of Intrinsic Microporosity

Polymers of intrinsic microporosity (PIM or here PIM-EA-TB) offer a highly rigid host environment into which hexachloroplatinate(IV) anions are readily adsorbed and vacuum carbonised (at 500 °C) to form active embedded platinum nanoparticles. This process is characterised by electron and optical microscopy, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and electrochemical methods, which reveal that the PIM microporosity facilitates the assembly of nanoparticles of typically 1.0 to 2.5-nm diameter. It is demonstrated that the resulting carbonised “Pt@cPIM” from drop-cast films of ca. 550-nm average thickness, when prepared on tin-doped indium oxide (ITO), contain not only fully encapsulated but also fully active platinum nanoparticles in an electrically conducting hetero-carbon host. Alternatively, for thinner films (50–250 nm) prepared by spin coating, the particles become more exposed due to additional loss of the carbon host. In contrast to catalyst materials prepared by vacuum-thermolysed hexachloroplatinate(IV) precursor, the platinum nanoparticles within Pt@cPIM retain high surface area, electrochemical activity and high catalyst efficiency due to the molecular rigidity of the host. Data are presented for oxygen reduction, methanol oxidation and glucose oxidation, and in all cases, the high catalyst surface area is linked to excellent catalyst utilisation. Robust transparent platinum-coated electrodes are obtained with reactivity equivalent to bare platinum but with only 1 μg Pt cm−2 (i.e. ~100% active Pt nanoparticle surface is maintained in the carbonised microporous host).Graphical ᅟ

A Highly-Durable CO-Tolerant Poly(vinylphosphonic acid)-Coated Electrocatalyst Supported on a Nanoporous Carbon.

For direct methanol fuel cells (DMFCs) to be commercialized, the durability of the anodic electrocatalyst needs to be highly considered, especially under high temperature and methanol concentration conditions. Low durability caused by carbon corrosion as well as carbon monoxide (CO) poisoning of the platinum nanoparticles (Pt-NP) leads to a decrease in active Pt-NPs and increases inactive Pt-NPs covered by CO species. In this study, we deposited Pt-NPs on poly[2,2'-(2,6-pyridine)-5,5'-bibenzimidazole] (PyPBI)-wrapped nanoporous carbon (NanoPC) and coated the as-synthesized electrocatalyst with poly(vinylphosphonic acid) (PVPA). The durability of the as-synthesized NanoPC/PyPBI/Pt/PVPA was tested in 0.1 M HClO4 electrolyte at 60 °C by cycling the potential from 1.0 to 1.5 V relative to RHE, and the results indicated that NanoPC/PyPBI/Pt/PVPA showed ∼5 times better durability relative to that of the commercial CB/Pt. The methanol oxidation reaction (MOR) of the electrocatalyst was tested before and after the potential cycling in the presence of 4 or 8 M methanol at 60 °C and found that the CO tolerance of the electrocatalyst was ∼3 times higher than that of the commercial CB/Pt. Such a higher CO tolerance is due to the coating of the PVPA, which was proven by an EDX mapping measurement. The NanoPC/PyPBI/Pt/PVPA showed a high durability and CO tolerance under high temperature and high methanol concentration conditions, indicating that the electrocatalyst could be used in real fuel applications.

Synthesis, Characterization, and Catalytic Applications of Core–Shell Magnetic Carbonaceous Nanocomposites

Magnetic resorcinol/formaldehyde resin (RF) and silica/RF nanocomposites with well-defined core–shell architecture and tunable structural parameters had been prepared via the extended Stöber method. The carbon counterparts with similar structure and morphology can be obtained by thermal-treating the polymer precursors under N2 atmosphere. The prepared materials were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, Mössbauer spectroscopy, N2 physical adsorption/desorption, and thermogravimetric analysis. The catalytic applications of the synthesized magnetic nanocomposites were also explored. It has been shown that the magnetite core was oxidized to γ-Fe2O3 during polymer coating process and further reduced to original Fe3O4 phase during carbonization. In addition, the iron oxide core can react with the shell when carbonization temperature reaches 700 °C. The structural stability of magnetic silica/RF is superior to magnetic RF because of the existence of an inner silica shell. Through a simple deposition–precipitate method, active platinum nanoparticles can be loaded in high dispersity onto the surface of the nanocomposites. The constructed magnetic catalysts are very active in hydrogenation of nitroarenes to corresponding amines and can be separated facilely with an external magnetic field.

Autonomous movement of platinum-loaded stomatocytes

Polymer stomatocytes are bowl-shaped structures of nanosize dimensions formed by the controlled deformation of polymer vesicles. The stable nanocavity and strict control of the opening are ideal for the physical entrapment of nanoparticles which, when catalytically active, can turn the stomatocyte morphology into a nanoreactor. Herein we report an approach to generate autonomous movement of the polymer stomatocytes by selectively entrapping catalytically active platinum nanoparticles within their nanocavities and subsequently using catalysis as a driving force for movement. Hydrogen peroxide is free to access the inner stomatocyte cavity, where it is decomposed by the active catalyst (the entrapped platinum nanoparticles) into oxygen and water. This generates a rapid discharge, which induces thrust and directional movement. The design of the platinum-loaded stomatocytes resembles a miniature monopropellant rocket engine, in which the controlled opening of the stomatocytes directs the expulsion of the decomposition products away from the reaction chamber (inner stomatocyte cavity).

Highly Active Platinum Nanoparticles on Graphene Nanosheets with a Significant Improvement in Stability and CO Tolerance

Graphene nanosheets (GNS) supporting Pt nanoparticles (PNs) are prepared using perfluorosulfonic acid (PFSA) as a functionalization and anchoring agent. Transmission electron microscope (TEM) results indicate that the prepared Pt NPs are uniformly deposited on GNS with a narrow particle size ranging from 1 to 4 nm in diameter. A high catalytic activity of this novel catalyst is observed by both cyclic voltammetry and oxygen reduction reaction (ORR) measurements due to the increasing of proton (H(+)) transmission channels. Significantly, this novel PFSA-functionalized Pt/GNS (PFSA-Pt/GNS) catalyst reveals a better CO oxidation and lower loss rate of electrochemical active area in comparison with that of the plain Pt/GNS and conventional Pt/C catalysts, indicating our PFSA-Pt/GNS catalysts hold much higher stability and CO tolerance by virtue of introduction of PFSA.

Controllable deposition of platinum nanoparticles on polyaniline-functionalized carbon nanotubes

We demonstrate a novel and very efficient interfacial polymerization method for the synthesis of high-quality polyaniline-wrapped carbon nanotubes (CNT–PANI), which represent a novel type of CNT–polymer heterostructure. The interfacial polymerization at the liquid–liquid interface is prone to form uniform core–shell CNT–PANI composites due to the presence of π–π interactions between PANI and CNT walls. Then electrocatalytically active platinum nanoparticles (Pt NPs) were loaded on the carbon nanotubes (CNT) through the introduction of electron-conducting PANI to bridge the Pt NPs and CNT walls with the presence of platinum–nitride (Pt–N) bonding and π–π bonding. The Pt NPs with controllable loading density were uniformly dispersed onto the CNT–PANI walls. The Pt/CNT–PANI hybrids possess exceptional electrochemical activity and exhibit excellent electrochemical stability towards methanol oxidation and oxygen reduction.

Highly catalytic activity of Pt electrocatalyst supported on sulphated SnO 2/multi-walled carbon nanotube composites for methanol electro-oxidation

Highly catalytic active platinum nanoparticles supported on sulphated SnO 2/multi-walled carbon nanotube composites (Pt–S–SnO 2/MWCNT) are reported. As a novel catalyst support, S–SnO 2/MWCNT composites with both electron and proton conductivity can improve the catalytic activity and utilization of Pt catalyst in direct methanol fuel cell. X-ray diffraction and transmission electron microscopy show that the sulphated SnO 2 and Pt nanoparticle is coexist in the Pt–S–SnO 2/MWCNT composites and coated uniformly on the surface of the MWCNTs. Fourier transform infrared spectroscopy analysis proves that the MWCNT surfaces are modified with sulphated SnO 2 and a high concentration of SO x , and adsorbed OH species exist on the surface of the sulphated SnO 2. Electrochemical studies are carried out using cyclic voltammetry, chronoamperometry and CO stripping voltammetry. The results indicate that Pt–S–SnO 2/MWCNT catalysts have much higher catalytic activity and CO tolerance for methanol electrooxidation than Pt-SnO 2/MWCNTs, commercial Pt/C and PtRu/C.