Electrocatalytic Properties For Methanol Oxidation Research Articles

Pt-O/Pt active sites and electrocatalytic properties for methanol oxidation enhanced dually by anatase/rutile TiO2 and BiOx

Understanding the details of how Pt-O/Pt active sites are boosted is essential for many catalytic reactions. Herein, different anatase/rutile (A/R) phase ratios of TiO2 nanoparticles (NPs) prepared by controlling calcination temperature (T), and irreversibly adsorbed Bi(III) are employed to dually improve the Pt-O/Pt active sites and their electrocatalytic activities. It is found that a T-dependent concave improvement trend is obtained on Pt/TiO2-T for the Pt-O/Pt active sites and electrocatalytic methanol oxidation rate. In the simultaneous presence of TiO2-T and BiOx, the electron-rich R(110) facet of TiO2-950 can promote the formation of bimetallic Bi-Pt sites, and the oxygen-acceptable Bi(III) is favorite for the electrochemical assembly of {Bi-Ox-Pt} active sites on the R(110) facet, further achieving a remarkable increase of 19.7-fold and 4.5-fold for the Pt-O/Pt active sites and electrocatalytic activity towards methanol oxidation compared with the case of bare Pt electrodes, respectively. The relationship between the Pt-O/Pt active sites and electrocatalytic properties is demonstrated, and the complete oxidation mechanism of methanol is proposed on BiOx-[Pt-TiO2-950] with reliable long-term durability. This study shows a new dually tuning strategy to maximize the utilization efficiency and anti-deactivated ability of Pt-based catalysts by TiO2-T and BiOx.

Low-temperature N-anchored ordered Pt3Co intermetallic nanoparticles as electrocatalysts for methanol oxidation reaction.

To enhance nanocatalyst performance and durability for the methanol oxidation reaction (MOR) in a direct methanol fuel cell, small-sized (2.1 nm) and structurally ordered Pt3Co intermetallic nanoparticles are uniformly anchored onto nitrogen-doped carbon nanotubes (N-CNTs) via a low-temperature N-anchoring method, and the N-doping abilities of different N-containing reagents are compared. After investigating the microstructure of Pt3Co/N-CNTs and evaluating their catalytic activity for the MOR, the results show that N-doping facilitates the uniform loading of Pt3Co NPs and plays a crucial role in improving the electrocatalytic activity of Pt3Co NPs supported on CNTs. Pt3Co/N-CNT-M with melamine as the N dopant exhibits the highest MOR activity and stability among all N-CNT-supported Pt3Co NPs and Pt/N-CNT-M. Density functional theory calculations suggest that the doping of N enhances the binding energy of CNTs to Pt3Co NPs, and the MOR mechanism shows that the introduction of Co is the reason for the enhancement of MOR reaction kinetics. The excellent electrochemical performance of Pt3Co/N-CNT-M is mainly attributed to the synergistic effect of N and Pt3Co intermetallic nanoparticles. The combination of ordered alloy nanoparticles and high-performance carrier N-CNT-M described herein exhibits great potential for fuel cells and may provide an unequivocal direction for the optimization of catalyst performance.

Controllable synthesis of grain boundary-enriched Pt nanoworms decorated on graphitic carbon nanosheets for ultrahigh methanol oxidation catalytic activity

A convenient and cost-effective approach is developed to produce ultrafine grain boundary-enriched Pt nanoworms grown on nitrogen-doped low-defect graphitic carbon nanosheets, which possess excellent electrocatalytic properties for methanol oxidation. • Controllable synthesis of 1D ultrafine Pt nanoworms is achieved. • Electronic-structure engineering endows the catalyst with numerous active sites. • The catalyst shows a high mass activity of 1949 mA mg −1 for methanol oxidation. • DFT calculations reveal the underlying catalytic mechanisms of the hybrid system. Although one-dimensional Pt nanocrystals have long been regarded as ideal electrode catalysts for fuel cells, the synthetic techniques commonly involve the use of various complicated templates or surfactants, which have largely hampered their large-scale industrial application. Herein, we present a convenient and cost-effective approach to the stereoassembly of quasi-one-dimensional grain boundary-enriched Pt nanoworms on nitrogen-doped low-defect graphitic carbon nanosheets (Pt NWs/NL-CNS). Benefiting from its numerous catalytically active grain boundaries as well as optimized electronic structure, the as-derived Pt NWs/NL-CNS catalyst possesses exceptionally good electrocatalytic properties for methanol oxidation, including an ultrahigh mass activity of 1949.5 mA mg −1 , reliable long-term durability, and strong poison tolerance, affording one of the most active Pt-based electrocatalysts for methanol oxidation reaction. Density functional theory calculation further reveals that the formation of worm-shape Pt morphology is attributed to the modified electronic structure as well as controllable defect density of the carbon matrix, which could also weaken the adsorption ability of Pt towards CO molecule and meanwhile synergistically promotes the catalytic reaction kinetics.

Formation of Bi-Containing sea urchin-like Pt nanoparticles induced by the addition of bismuth element and their enhanced electrocatalytic properties for methanol oxidation

A facile method to synthesize Bi-containing sea urchin-like Pt nanoparticles is demonstrated. The morphology and chemical composition of the prepared Bi-containing sea urchin-like Pt nanoparticles were characterized using scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Electrochemical studies of the oxidation of methanol in an acidic medium using the Bi-containing sea urchin-like Pt nanoparticles were performed. The prepared nanoparticles exhibited enhanced electrocatalytic activity for methanol oxidation with a seven-fold higher oxidation current density and a more negative onset potential than commercial Pt/C (Pt 20%). Moreover, the current density of the Bi-containing sea urchin-like Pt nanoparticle/C catalysts was high even after 900 s of continuous electrocatalysis at 0.56 V. The synthesized Bi-containing sea urchin-like Pt nanoparticles should find attractive applications in various fields, such as fuel cells, sensors, and eletro- or organic catalysis.

Synthesis of Nanostructured Bimetallic Catalysts for Electrochemical Applications

Bimetallic nanostructures of specific compositions and enclosed by certain facets can significantly alter their physical and chemical properties and thus provide the opportunities to tailor them for particular electrochemical applications. Despite significant progress in recent years, it is still a grand challenge to control the spatial distribution of elements and surface structure of bimetallic nanoparticles. Thus, it remains very difficult to understand the properties of bimetallic nanoparticles, and even more challenging to overcome the formidable barriers to the rational design of bimetallic nanoparticles with the desired performance. This research focuses on the development of seed-mediated synthesis in solution aiming to precisely control the atomic arrangement in the bimetallic catalysts to establish the structure-composition-property relationship for electrocatalytic applications. In seed-mediated synthesis, the seeds can be preformed or in situ formed as a primary nanoscale substrate, followed by reducing secondary precursors to form bimetallic or multimetallic nanocatalysts. By controlling the shape of the seeds and reduction kinetics, well-defined bimetallic and multimetallic nanostructures can be obtained. In this work, CuPt and CuPtRu nanomaterials will be used as an example to demonstrate how changes of spatial atomic arrangement in the nanostructures influence their electrocatalytic properties for methanol oxidation. Fine tuning and mechanistic study of these synthetic strategies provide us fundamental understanding for precise control of bimetallic nanostructures to tackle problems in materials chemistry and open up the possibility for rational design and synthesis of future complex nanoarchitectures towards electrochemical applications.

Fabrication of a composite of platinum, N-g-C3N4 and Ketjen Black for photo-electrochemical methanol oxidation

Recently N-doped graphitic carbon-incorporated g-C3N4 (denoted as N-g-C3N4) exhibits better electroconductivity and photo-catalytic property compared with pure g-C3N4 as a support material for Pt nanoparticles (NPs). A composite catalyst consisting of Pt nanoparticles and N-g-C3N4-modified KB was designed and fabricated. Pt nanoparticles were prepared through a solution plasma process; N-g-C3N4 was prepared by direct heating the mixture of urea and citric acid monohydrate and subsequently treated by hydrothermal method. Their chemical composition, particle size and microstructure were investigated by X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. Compared with the Pt/KB catalyst, ternary Pt/N-g-C3N4/KB nanocomposites exhibit excellent electrocatalytic properties for methanol oxidation owning to the significant synergistic effects of individual components. Once light irradiation was supplied, Pt/N-g-C3N4/KB catalyst exhibits exceptional forward peak current densities as high as 2800 mA mg Pt −1 . And Pt/N-g-C3N4/KB catalyst also shows better CO tolerance than Pt/KB. Such a Pt/N-g-C3N4/KB composite catalyst may bring new design ideas for photo-assisted direct methanol fuel cell in the future.

Heterostructures in carbon-doped tungsten nitride and its effect on electrocatalytic properties for methanol oxidation

The hexagonal carbon-doped tungsten nitride nanoparticles (WC|N) have been derived from the cubic WN by inducing carbon atoms to WN lattices via a controlled carbonization method. The heterostructures discrepancy in WC|N catalysts involving constitutions of crystal phases and concentration of carbon and nitrogen could be effectively adjusted by simply changing carbonization time, and then had a great impact on the electrocatalytic behaviors of WC|N. Porous morphology of WC|N catalysts was also inherited from tungsten nitrides to provide the large surface area. The ternary Pt/WC|N catalysts were fabricated by an ethylene glycol reduction method with microwave-assisted heating. The intimate contact and intensive interaction between Pt and WC|N catalyst were verified. Impressively, the Pt/WC|N hybrid exhibited superior electrocatalytic activity for methanol oxidation and improved CO anti-poisoning capacity which higher than that of commercial Pt/C catalyst. The catalytic activity was enhanced due to the large amount of distortion which was induced during the diffusion of C into WN lattice and resultant phase transformation. Samples which were carbonized for 120min displayed the outstanding catalytic activity among all the materials even from the different tungsten sources suggest that the extent of distortion in catalyst is the crucial factor for the catalyst activity in electrochemistry reaction.

Electrocatalytic performance of Ni-Ti-O nanotube arrays/NiTi alloy electrode annealed under H2 atmosphere for electro-oxidation of methanol

In the present study, Ni-Ti-O nanotube arrays (Ni-Ti-O NTs) were fabricated by anodizing NiTi alloy in a mixed solution consisted of ethylene glycol and glycerol. Then the Ni-Ti-O NTs were suffered annealing treatment under hydrogen atmosphere, leading to the significant improved electrocatalytic performance. The morphologies, the phases and the surface electronic states of Ni-Ti-O NTs samples before and after annealing were characterized by SEM, XRD and XPS, respectively. And their electrocatalytic properties for methanol oxidation were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in the alkaline media. Results show that electrocatalytic activity of the Ni-Ti-O NTs samples annealed under H2 exhibits a significant improvement because of the increases of the conductivity and the active sites provided by reduction of Ni3+. The Ni-Ti-O NTs samples with lower crystallinity annealed at 500 °C for 2 h have better electrocatalytic performance for methanol electro-oxidation in alkaline medium. The peak current density increases after a consecutive sweep for 1000 times and varies indistinctively after placing in the air for 30 days, indicating the excellent long-term electrocatalytic stability. The in situ formation of Ni-base material catalyst in Ni-Ti-O nanotube benefits improvement of the catalytic properties during long-term operation. The Ni-Ti-O NTs/Ni-Ti alloy is a desirable substitute of catalysts support material or it is also a promising electrocatalytic electrode for direct methanol fuel cells.

Effect of nitrogen-doped PtRu/graphene catalyst on its activity and durability for methanol oxidation

Pt–Ru catalysts are highly regarded and investigated by many investigators. However, how to reduce Ru dissolution remains a major concern for their applications under realistic operating conditions. In this study, nitrogen-doped graphene supporting PtRu catalyst was synthesized by a mild microwave-assisted ethanol reduction process, which exhibited superior electrocatalytic properties for methanol oxidation. The morphologies and microstructures of the as-prepared catalysts were characterized by transmission electron microscopy and X-ray photoelectron spectroscopy. Long-term catalytic stability was evaluated by the accelerated aging cyclic voltammetry test. The results reveal that N-doping is beneficial for the minimization of metal migration and coalescence, and meanwhile it slows Ru dissolution.

Facile synthesis of graphene nanoplate-supported porous Pt–Cu alloys with high electrocatalytic properties for methanol oxidation

A porous Pt1Cu1 alloy nanocrystal catalyst supported on 1-aminopyrene functionalized graphene nanoplates, which is a highly active catalyst for methanol oxidation in alkaline medium, is synthesized by a one-step method without any high boiling point organic solvents, surfactants, stabilizers and templates.

Electrodeposition of PtNi Nanosheets on Flexible PET/ITO Substrate and their Electrocatalytic Properties for Methanol Oxidation

We report a facile synthesis of PtNi nanosheets on the flexible ITO/PET substrate by electrochemical deposition method. The morphology and composition of the PtNi nanosheets were characterized and it was revealed that the PtNi nanosheets were polycrystalline with a thickness of about 4 nm. The average Ni content in the nanosheets was about 10 at%. The results of the electrochemical measurements showed that the PtNi nanosheets have excellent catalytic activity and stability toward the electro-oxidation of methanol in alkaline medium, which making it more attractive for fuel cell applications.

One step preparation of ‘ready to use’ Au@Pd nanoparticle modified surface using deep eutectic solvents and a study of its electrocatalytic properties in methanol oxidation reaction

A facile one pot synthesis andin situelectrodeposition of Au–Pd core–shell nanoparticles (Au@Pd NPs) could be achieved in a deep eutectic solvent. The fabricated Au@Pd NPs modified graphite showed superior electrocatalytic properties for methanol oxidation at low activation energies.

Synthesis of Pt-Au/C Composite Catalysts with Different Au Compositions and Their Electrocatalytic Properties for Methanol Oxidation

Synthesis of Pt-Au/C Composite Catalysts with Different Au Compositions and Their Electrocatalytic Properties for Methanol Oxidation

Additive-free macroscopic-scale synthesis of coral-like nickel cobalt oxides with hierarchical pores and their electrocatalytic properties for methanol oxidation

Coral-like nickel cobalt oxides with hierarchical pores were massively synthesized via a one-pot additive-free solvent thermal decomposition route coupled with a post calcination treatment. The physicochemical properties of nickel cobalt oxides were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS) and nitrogen sorption measurements. The unique 3D hierarchical porous NiCo2O4 coral structures exhibit enhanced electrocatalytic properties for methanol oxidation with a desirable stability. The large-scale and facile additive-free synthetic technique can be applied to the construction of other metal oxide with complex hierarchical structures.

Pulsed electrodeposition of Pt particles on indium tin oxide substrates and their electrocatalytic properties for methanol oxidation

The platinum (Pt) particle electrocatalysts supported on the indium tin oxide (ITO) substrate were prepared by the pulsed electrodeposition for the methanol oxidation. The effect of the lower potential pulse duration (tl) of the electrodeposition on the surface morphology and structure of the Pt particles was investigated by the X-ray diffraction and scanning electron microscopy. The amount of the Pt loading was determined by an inductively coupled plasma method, and the electrocatalytic activity of the prepared Pt electrocatalysts on the ITO for the methanol oxidation was characterized by cyclic voltammetry. The results showed that the tl has a significant influence on the surface morphology of the Pt particles on the ITO substrate. As the tl decreases from 1 to 0.01s, the deposited Pt particles on the ITO exhibit flower-, nanosheet-, prickly and smooth spherical-like morphology in turn. Furthermore, there is a remarkable effect of the surface morphology of the Pt particles on the electrocatalytic activity for the methanol oxidation. Among all these morphologies, the flower- and nanosheet-like Pt particles on the ITO have a much higher mass specific activity (MA) for the methanol oxidation, and the Pt particles with prickly surface followed while the smooth spherical Pt particles have the lowest MA. In particular, the dispersed Pt nanosheets prepared at tl of 0.5s has the highest MA. The much improved MA of the dispersed Pt nanosheets is attributed not only to the large electrochemically active surface area (ECSA) achieved, but also to the high electrocatalytic activity per unit ECSA related to its special morphology.

Monodispersed Pd nanospheres and their electrocatalytic properties for methanol oxidation in alkaline medium

High-dispersed Pd nanospheres were synthesized successfully by a facile and green method using polyoxypropylenepolyoxyethylene copolymer as reducer and stabilizer. The size and shape of the nanospheres can be well controlled through simply varying the reaction temperature. The morphology and structure of the nanospheres were characterized by Transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray powder diffraction (XRD). The electrocatalytic test indicated that the obtained Pd nanospheres exhibit more negative onset oxidation potential and much higher current density for methanol oxidation in alkaline media compared to the bulk Pd electrode. The results of this paper provides a promising approach to prepare Pd-based nanocatalysts for alkaline fuel cells.

Large-scale electrosynthesis of Pd nanodendrites and their improved electrocatalytic properties for methanol oxidation

Using glassy carbon electrodes (GCE) as working electrodes, Pd nanodendrites have been prepared on a large scale by one-step electrodeposition, without any seed or surfactant, just with the assistance of ethylenediamine. The formation of Pd nanostructures is closely associated with their growth conditions, such as applied potential, electrolyte and its concentration, and electrodeposition time. It is found that Pd nanocrystals are preferential growing along the (111) directions during the electrolysis process. The as-prepared Pd dendrites have large electroactive surface area and exhibit high electrocatalytic ability towards methanol oxidation, which can be used as a better potential candidate for application in direct fuel cells.

Synthesis and characterization of PtCo nanowires for the electro-oxidation of methanol

PtxCo100−x (60≤x≤100) 1D nanostructures (nanowires) on titanium are prepared by direct electrodeposition throughout a porous anodic aluminum oxide membrane and analyzed for methanol electrooxidation. For comparison, thin films of the same composition are also prepared. The morphology and composition are characterized by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). A model based on the simultaneous deposition of Pt and Co underpotential deposition (UPD) on Pt was devised to understand how the composition varies with the electrodeposition potential. The deposition rates were determined by means of an Electrochemical Quartz Crystal Microbalance (EQCM). PtxCo100−x alloy formation was confirmed by X-ray diffraction (XRD). Electrocatalytic properties for methanol oxidation are investigated by cyclic voltammetry (CV) in 1.0M CH3OH+0.5M H2SO4. The results show that PtCo nanowires yield to an enhancement (by a factor of 5) of the exposed surface area (m2g−1). In the presence of CH3OH, If/Ib ratio of Pt rich nanowires is systematically higher than for thin films with the same composition. If/Ib ratio of Pt90Co10 nanowires is 1.59, larger than that of pure Pt (If/Ib=0.76–0.87) and commercially available PtCo deposited on carbon support (If/Ib=1.32).

Electrocatalysis of Ni-promoted Cd coated graphite toward methanol oxidation in alkaline medium

The nickel–cadmium (Ni-promoted Cd) catalyst for using direct methanol fuel cell (DMFC) applications is electrochemically deposited on a graphite substrate. The activity of methanol oxidation is assessed by recording cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA) techniques. The surface morphologies and chemical compositions of catalysts are determined by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray florescence spectroscopy (XRF). Mean roughness of catalysts is measured by atomic force microscopy (AFM). Kinetic parameters of oxidation such as the anodic electron transfer coefficient (αa), cathodic electron transfer coefficient (αc) and charge transfer rate constant (ks) are calculated. The effect of methanol concentration and temperature on methanol oxidation is also investigated. The electrochemical measurements show that the addition of Cd to single coating enhances the electrocatalytic properties for methanol oxidation and Ni-promoted Cd/C has the best catalytic activity and stability.

Platinum nanoflowers supported on graphene oxide nanosheets: their green synthesis, growth mechanism, and advanced electrocatalytic properties for methanol oxidation

This paper reports a nontoxic, rapid, one-pot and template-free synthesis of three-dimensional (3D) Pt nanoflowers (PtNFs) with high yield and good size monodispersity supported on graphene oxide (GO) nanosheets. The key synthesis strategy employed a low-cost, green solvent, ethanol as the reductant and an advanced, powerful 2D carbon material, GO nanosheets as the stabilizing material. The resulting PtNFs-GO nanosheets were characterized by transmission electron microscopy (TEM), high-resolution TEM, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and electrochemical techniques. It was found that the monodispersed, porous PtNFs supported on GO nanosheets were a uniform size of 30 nm and each was composed of numerous “clean” and small (4 nm) Pt nanoparticles, which revealed an unusually high activity for methanol oxidation reaction compared to commercial Pt black. Furthermore, based on a systematic study of the PtNFs growth conditions, a possible mechanism, and especially the importance of GO in the formation was proposed. Our study demonstrates that GO is a promising support material for developing next-generation advanced Pt based fuel cells and their relevant electrodes in the field of energy.