Electrospinning-derived carbon fibrous mats improving the performance of commercial Pt/C for methanol oxidation

The carbon fibrous mats (CFMs) formed by carbon nanofibers whose average diameter is about 150 nm have been fabricated by thermally treating the electrospun polyacrylonitrile fibrous mats. The electrocatalytic activity of commercial Pt/C supported on the CFMs for methanol oxidation in a sulfuric acid solution has been investigated by cyclic voltammetry, chronoamperometry, quasi-steady state polarization, and electrochemical impedance spectroscopy (EIS) methods. The results show that the commercial Pt/C supported on the CFMs exhibits higher electrocatalytic activity, more stability, larger exchange current and smaller charge transfer resistance than that on commercial carbon papers (CPs), which reveals that the CFMs could be developed as suitably-supporting materials for Pt/C catalyst due to their special porous and continuous fibrous structures.     

Titanium carbide nanoparticles supported Pt catalysts for methanol electrooxidation in acidic media

Titanium carbide (TiC) nanoparticles supported Pt catalyst for methanol electrooxidation is investigated for the first time. The resultant TiC/Pt catalysts are prepared by using a simple electrodeposition to load Pt nanoparticles on TiC nanocomposite. The electrodes are characterized by scanning electron microscopy and cyclic voltammetry. It is found that the TiC/Pt catalysts help alleviate the CO poisoning effect for methanol electrooxidation with a higher ratio of the forward anodic peak current (I_f) to the reverse anodic peak current (I_b). The improvement in the catalytic performance is attributed to the fact that TiC ameliorates the tolerance to CO adsorption on Pt nanoparticles. One possible mechanism to improve the CO tolerance of Pt taking TiC as supporting material in methanol electrooxidation is also proposed. The results suggest that TiC could be practical supporting materials to prepare electrocatalysts that are suitable for the methanol electrooxidation applications.     

Synthesis and electrocatalysis of 1-aminopyrene-functionalized carbon nanofiber-supported platinum-ruthenium nanoparticles

Platinum-ruthenium/carbon composite nanofibers were prepared by depositing PtRu nanoparticles directly onto electrospun carbon nanofibers using a polyol processing technique. The morphology and size of PtRu nanoparticles were controlled by 1-aminopyrene functionalization. The noncovalent functionalization of carbon nanofibers by 1-aminopyrene is simple and can be carried out at ambient temperature without damaging the integrity and electronic structure of carbon nanofibers. The resulting PtRu/carbon composite nanofibers were characterized by cyclic voltammogram in 0.5 M H₂SO₄ and 0.125 M CH₃OH + 0.2 M H₂SO₄ solutions, respectively. The PtRu/carbon composite nanofibers with 1-aminopyrene functionalization have smaller nanoparticles and a more uniform distribution, compared with those pretreated with conventional acids. Moreover, PtRu/1-aminopyrene functionalized carbon nanofibers have high active surface area and improved performance towards the electrocatalytic oxidation of methanol.     

Platinum nanoparticles supported on activated carbon fiber as catalyst for methanol oxidation

Activated carbon fiber (ACF) with high specific surface area has been used as support in the preparation of Pt nanoparticles electrocatalyst (Pt/ACF) for direct alcohol fuel cells. It is found that the Pt nanoparticles on ACF are highly and homogeneously dispersed with a narrow size distribution in the range of 1.5–3.5 nm with an average size of 2.4 nm. In comparison with the commercial E-TEK Pt/C catalyst, the Pt/ACF catalyst exhibits much higher catalytic activity for methanol, ethanol and isopropanol oxidation, which are about 2.4 times as high as that of the former. The Pt/ACF catalyst is observed to be significantly more stable during the constant current density polarization and continuous cyclic voltammetry in comparison with Pt/C catalyst. Both the uniform dispersion of Pt nanoparticles and strong interactions between Pt nanoparticles and ACF are of benefit to achieve the performance improvement of Pt/ACF catalyst.     

Saccharide-based graphitic carbon nanocoils as supports for PtRu nanoparticles for methanol electrooxidation

Highly graphitic carbon nanocoils were synthesised from the catalytic graphitization of carbon spherules obtained by the hydrothemal treatment of different saccharides (sucrose, glucose and starch). This nanostructured carbon was characterized by X-ray power diffraction, N₂ adsorption and microscopy techniques (SEM and TEM). The carbon nanocoils were used as a support for PtRu nanoparticles, which were well-dispersed over the carbon surface. This catalytic system was investigated for use as an electrocatalyst for methanol electrooxidation in an acid medium. The experiments were carried out at two working temperatures (25 °C and 60 °C). It was found that the carbon nanocoils supporting PtRu nanoparticles exhibit a high catalytic activity, which is even higher than that of conventional carbon supports (Vulcan XC-72R). We believe that the high electrocatalytic activity of the carbon nanocoils presented here is due to the combination of a good electrical conductivity, derived from their graphitic structure, and a wide porosity that allows the diffusional resistances of reactants/products to be minimized.     

Synthesis and characterization of Pt nanoparticles on sulfur-modified carbon nanotubes for methanol oxidation

Pt nanoparticles supported on carbon nanotubes (Pt/CNTs) have been synthesized from sulfur-modified CNTs impregnated with H₂PtCl₆ as Pt precursor. The dispersion and size of Pt nanoparticles in the synthesized Pt/CNT nanocomposites are remarkably affected by the amount of sulfur modifier (S/CNT ratio). The results of X-ray diffraction and transmission electron microscopy indicate that an S/CNT ratio of 0.3 affords well dispersed Pt nanoparticles on CNTs with an average particle size of less than 3 nm and a narrow size distribution. Among different catalysts, the Pt/CNT nanocomposite synthesized at S/CNT ratio of 0.3 showed highest electrochemically active surface area (88.4 m² g⁻¹) and highest catalytic activity for methanol oxidation reaction. The mass-normalized methanol oxidation peak current observed for this catalyst (862.8 A g⁻¹) was ∼ 6.5 folds of that for Pt deposited on pristine CNTs (133.2 A g⁻¹) and ∼ 2.3 folds of a commercial Pt/C (381.2 A g⁻¹). The results clearly demonstrate the effectiveness of a relatively simple route for preparation of sulfur-modified CNTs as a precursor for the synthesis of Pt/CNTs, without the need for tedious pretreatment procedures to modify CNTs or complex equipments to achieve high dispersion of Pt nanoparticles on the support.     

Silicotungstic acid stabilized Pt–Ru nanoparticles supported on carbon nanofibers electrodes for methanol oxidation

Silicotungstic acid stabilized Pt–Ru nanoparticles supported on Functionalized Carbon Nanofibers have been prepared by a microwave-assisted polyol process. The samples were characterized by XRD, SEM and TEM analysis. The electro-catalytic activities of the prepared composites (20% Pt–Ru/STA–CNF) were examined by using Cyclic Voltammetry (CV) for oxidation of methanol. The electro-catalytic activity of the carbon nanofiber based composite (20% Pt–Ru/STA–CNF) electrode for methanol oxidation showed better performance than that of commercially available Johnson Mathey 20% Pt–Ru/C and 20% Pt–Ru/STA–C catalyst. The results imply that carbon nanofiber based STA composite electrodes are excellent potential candidates for application in direct methanol fuel cells.     

Platinum nanoparticles anchored on aminated silica@PEDOT-PSS hybrid for enhanced methanol oxidation electrocatalysis

Direct methanol fuel cell (DMFC) with near-zero pollution emission, large energy density, and low operating temperature provides a beneficial and sustainable way for alleviating fossil energy crisis and ecological pollution issues. In this work, a systematic protocol was explored for the design of novel electrocatalyst based on PEDOT-PSS coated amino-functionalized SiO₂ microspheres (SiO₂–NH₂@PEDOT-PSS) support, and then Pt nano-particles (NPs) were uniformly anchored for the anodic process of DMFCs. Characterization techniques, e.g. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed that the dispersity and homogeneity of Pt NPs on the surface of SiO₂–NH₂@PEDOT-PSS were markedly improved due to PEDOT-PSS modification, and the distribution of Pt NPs was in a smaller mean-size ~2.8 nm. Subsequently, X-ray photoelectron spectroscopy (XPS) study exposed fast electron shift phenomenon from SiO₂–NH₂@PEDOT-PSS support to Pt NPs in the catalyst. The various electrochemical tests such as cyclic voltammetry (CV), chronoamperometry (CA) and impedance spectroscopy (EIS) revealed that the prepared Pt/SiO₂–NH₂@PEDOT-PSS catalyst presented higher electrocatalytic efficacy, excellent durability with improved CO-tolerance towards methanol oxidation reaction rather than commercial Pt/C catalyst. These distinctive physical and chemical features of designed catalyst raise the spirit to design an efficient electrocatalyst based on Pt/SiO₂–NH₂@PEDOT-PSS in DMFC applications.     

Synthesis of carbon nanofibers/poly(para-phenylenediamine)/nickel particles nanocomposite for enhanced methanol electrooxidation

Several studies have been conducted on direct methanol fuel cells (DMFCs) to resolve major issues such as the high cost of the catalyst and the poisoning of the electrode. Herein, a low-cost catalyst based on nickel particles (NiPs), carbon nanofibers (CNF) and poly(para-phenylenediamine) (PpPD) was carried out using a simple electrochemical method. The morphology and structure of the nanocomposite electrodes are characterized by field-emission gun scanning electron microscopy coupled with an energy dispersive X-ray detector, X-ray diffraction, Fourier transform infrared spectroscopy and Raman spectroscopy. The effects of various parameters such as the PpPD film thickness and the NiPs content on the electrocatalytic performance of CPE/CNF/PpPD/NiPs are evaluated which lead to the optimized composition. The results of the methanol electrooxidation reaction at room temperature showed that the optimized CPE/CNF/PpPD/NiPs nanocomposite exhibits a high catalytic activity (I_p = 38.11 mA cm⁻²), good stability and durability for more than 6 h in comparison with CPE/CNF/NiPs. These findings truly highlight the synergetic effect of CNF/PpPD in enhancing the electrochemical activity and stability and the vast potential of CPE/CNF/PpPD/NiPs as low-cost catalyst and electrodes for DMFCs.     

Effect of Co in the efficiency of the methanol electrooxidation reaction on carbon supported Pt

The effect of Co addition to carbon nanotubes supported Pt in the methanol oxidation reaction has been investigated by means of differential electrochemical mass spectrometry (DEMS). It has been observed that the CO₂ efficiency increases in carbon nanotubes supported PtCo compared to its homologous Pt catalysts, especially at potentials lower than 0.55 V. Despite of this, the Faradaic current reached by the bimetallic catalysts in the methanol electrooxidation was lower than those recorded on the monometallic samples. This is because Co addition difficult finding enough Pt vicinal sites for methanol dehydrogenation. On the other hand, it has been found that alloying Pt with Co, shifts down the d-band center of the larger element, so the strength of the interaction with adsorbates decreases. Consequently, it will be easier to oxidize CO_ad on the bimetallic surface. Furthermore, the necessary -OH_ad species for the CO_ad oxidation to CO₂ will be provided by the CNTs themselves.     

Excellent electrocatalysis of methanol oxidation on platinum nanoparticles supported on carbon-coated silicon

The prepared carbon-coated silicon (Si@C) material was blended with graphite powder together to form the specific carbon paste electrode with different mass percent X% of Si@C (CPE-Si@C(X%)). The electrochemical impedance spectroscopy (EIS) was performed on the prepared CPE-Si@C and the pure carbon paste electrode (CPE), and the results show that the CPE-Si@C (X%) electrode has a smaller charge transfer resistance. Pt/CPE and Pt/CPE-Si@C(X%) electrodes were prepared by electrodepositing Pt particles on CPE-Si@C and CPE, and the obtained electrodes were used for electrocatalytic oxidation of methanol in acid media. The results show that the activity of Pt/CPE-Si@C(X%) electrode for electrocatalytic oxidation of methanol was higher than that of Pt/CPE electrode, and the mass peak current density of Pt/CPE-Si@C(10%) electrode for electrocatalytic oxidation of methanol reached 321 mA mg^?1, which was 1.8 times higher than that of Pt/CPE electrode. The Pt/CPE-Si@C (10%) electrode and the Pt/CPE electrode were characterized by chronoamperometry. The results show that Pt/CPE-Si@C (10%) has a better stability of activity and stronger tolerance against CO poisoning.     

Novel hollow PtRu nanospheres supported on multi-walled carbon nanotube for methanol electrooxidation

A multi-walled carbon nanotube supported hollow PtRu nanosphere electrocatalysts was prepared at room temperature in a homogeneous solution employing cobalt metal nanoparticles as sacrificial templates. Transmission electron micrograph (TEM) measurements showed that carbon nanotube supported PtRu nanospheres were coreless and composed of discrete PtRu nanoparticles with the crystallite size of about 2.1 nm. X-ray diffraction (XRD) results showed that the hollow PtRu nanospheres had a face-centered cubic structure. Electrochemical measurements demonstrated that the carbon nanotube supported hollow PtRu nanosphere electrocatalysts exhibited enhanced electrocatalytic performance for methanol oxidation compared with carbon nanotube supported solid PtRu nanoparticles and commercial E-TEK PtRu/C (20 wt%) catalysts, which is crucial for anode electrocatalysis in direct methanol fuel cells (DMFCs).     

Oxidized carbon nanofibers supporting PtRu nanoparticles for direct methanol fuel cells

Oxidized carbon nanofibers (CNFs) have been investigated as supports for PtRu nanoparticles. Two distinct CNFs characterized by different surface area and crystallinity have been considered and treated with nitric acid and a mixture of sulfuric and nitric acids to introduce oxygen functionalities. The oxidized CNFs have been then physico-chemically characterized and used for the preparation of PtRu/CNF catalysts by a modified microemulsion procedure. PtRu nanoparticles of ca. 2 nm size were obtained despite the relatively low surface area of CNFs (90–180 m² g⁻¹). A good particle distribution on the supports has been obtained, as confirmed by TEM micrographs and by the high values of electrochemically active surface areas (up to 200 m² g⁻¹). Catalysts based on oxidized carbon nanofibers present a significant increase of activity toward the electro-oxidation of methanol. The effect of oxidation treatments is not independent of the CNF properties, which must be considered for a convenient support optimization. Nevertheless, the optimum support is obtained when balancing three parameters: a sufficient electrochemical surface area, an improved metal-support interaction due to the effect of oxygen functionalities, and better methanol diffusion through the catalyst pores due to the wettability of oxidized CNFs.     

Nontrivial role of carbon nanofibers morphology in binderless Pt nanocatalyst supported electrode

Similar to conventional composite electrodes, developing binderless-based carbon nanostructured (CNs) electrodes for fuel cells requires particularly the optimisation of both the morphology and the density of the CNs. In this work, carbon nanofibers (CNFs) have been optimised and used as catalyst support for Pt nanoparticles (NPs). The nontrivial role of the CNFs on the catalytic behavior is clearly demonstrated. We have shown that for a similar amount, morphology and dispersion of the Pt NPs fabricated onto CNFs, the density of the latter and to a lesser extent their diameter are the main factors influencing the catalytic activity. For the particular case of CNFs considered in this work, an optimum activity toward methanol fuel cell reaction was obtained when Pt NPs were supported with CNFs synthesized with a C₂H₂/Ar ratio of 0.31.     

Pt supported on boron,nitrogen co-doped carbon nanotubes (BNC NTs) for effective methanol electrooxidation

The research for electrocatalyst with high electroactivity and great CO-resistance ability for direct methanol fuel cells (DMFCs) is still a huge challenge. In this report, we develop Boron, Nitrogen co-doped carbon nanotubes (BNC NTs) as a support for Pt. Owing to the doping of boron, the catalyst not only provides extremely active sites for methanol oxidation reactions (MOR) but also protects Pt nanoparticles from agglutinating, performing superior electroactivity and excellent ability to anti CO poisoning. The X-ray photoelectron spectroscopy (XPS) results demonstrate the strong electron effect between Pt and B. Notably, the Pt/BNC NTs catalyst exhibits higher catalytic activity towards MOR and more superior durability in comparison with Pt/NC NTs and commercial JM Pt/C catalyst. The accelerated durability test (ADT) illustrates that Pt/BNC NTs catalyst can improve the issue of electrochemical surface area (ECSA) conservation, with only 30% diminish in comparison with the initial ECSA after 5000 cycles. The experiment result demonstrate that boron doping is the key step to improve the catalytic activities and CO-resistance ability due to the combination effects, involving firm B–C and N–C bonds, the stronger electron transfer in the nanotube structure among Pt, B and N, the stronger adsorption intensity of oxygen species from doped B.     

Pt nanoparticles supported on titanium iron nitride nanotubes prepared as a superior electrocatalysts for methanol electrooxidation

Titanium iron nitride (Ti_0.95Fe_0.05N) supports with one-dimensional (1D) hollow and porous nanotubes(Ti_0.95Fe_0.05N NTs)are prepared by a two-step method, including hydrothermal method followed post-nitriding treatment. Pt nanoparticles (NPs) are further supported on Ti_0.95Fe_0.05N NTs for methanol electrooxidation. The experimental results reveal that the prepared material is Ti_0.95Fe_0.05N NTs with high purity, and this support is characterized by a porous tubular structure with hollow walls and large specific surface area. The X-ray photoelectron spectroscopy (XPS) pattern shows the strong interaction between the robust Ti_0.95Fe_0.05N NTs support and uniform Pt NPs catalyst. In addition, the electrochemical data demonstrate that Ti_0.95Fe_0.05N NTs loaded Pt NPs (Pt/Ti_0.95Fe_0.05N) display greatly improved activity and stability than that of Pt/C catalyst. The significantly enhanced durability of the hybrid electrocatalysts and electrochemical surface area (ECSA) preservation of the catalyst are observed after the accelerated durability test (ADT). The experimental data verify that the introducing of Fe can tune the electronic structure of Pt atoms, which contributes to the strengthened activity and stability of the Pt catalyst for the methanol oxidation reaction.     

Palladium nanoparticles supported by three-dimensional freestanding electrodes for high-performance methanol electro-oxidation

Palladium (Pd) nanoparticles (NPs) prepared by gas phase cluster deposition demonstrated excellent electrocatalytic activity. Herein, a series of Pd NPs modified freestanding electrodes with a super clean surface and easy repeating process for methanol oxidation reaction is reported. Pd NPs with different coverage were deposited on Ni foams and three-dimensional graphene-Ni foams, respectively. Owning to the special three-dimensional structure of Ni foam, the Pd NPs-Ni foam composite exhibited remarkable activity and unusually long-term stability for methanol electro-oxidation. The introduced three-dimensional graphene prepared by conventional chemical vapour deposition improved the electrocatalytic performance. The results can be attributed to the Pd NPs with high electrochemical activity and unique properties for three-dimensional supports.     

Testing of carbon supported Pd-Pt electrocatalysts for methanol electrooxidation in direct methanol fuel cells

In the present work, a detailed characterization of the electrochemical behavior of carbon supported Pd-Pt electrocatalysts toward CO and methanol electrooxidation in direct methanol fuel cells is reported. Technical electrodes containing an ionomer in their catalyst layer were prepared for this purpose. CO and methanol electrooxidation reactions were used as test reactions to compare the electrocatalytic behavior of bimetallic supported nanoparticles in acidic liquid electrolyte and in solid polymer electrolyte (real fuel cell operating conditions). Experimental results in both environments are consistent and show that the electrochemical behavior of carbon supported Pd-Pt depends on their composition, giving the best performance in direct methanol single fuel cell with a Pd:Pt atomic ratio of 25:75 in the catalyst.     

A highly active Pt nanocatalysts supported on RuO2 modified TiO2-NTs for methanol electrooxidation with excellent CO tolerance

Poisoning devitalization of Pt catalyst caused by the absorption of carbon monoxide is an important issue in direct Methanol Fuel Cell (DMFC). To solve this problem, this work introduced a novel nano-structured Pt catalytic electrode, in which RuO₂ modified TiO₂ nanotube arrays (TiO₂-NTs) was used as a carrier for the load of Pt nanocatalysts. Specifically, RuCl₃ sol was filled into the voids of TiO₂-NTs under vacuum condition, followed by thermal decomposition to form RuO₂/TiO₂-NTs support, and then Pt particles were loaded on the RuO₂/TiO₂-NTs support by pulse potential electrodeposition from H₂PtCl₆ aqueous solution. The electrochemical results show that the methanol oxidation current on Pt/RuO₂/TiO₂-NTs is much higher than that on Pt/TiO₂-NTs. In addition, the current attenuation on Pt/RuO₂/TiO₂-NTs with the increased scan cycle is also decreased. The Pt/RuO₂/TiO₂-NTs electrode with 8 g m⁻² RuO₂ exhibits the most stable performance, indicating a strong effects of anti CO poisoning endowed by RuO₂. In Nyquist diagrams, one capacitance arc representing the action of deprivation of H atom appears in the first quadrant and one inductance arc representing the action of deprivation of CO appears in the fourth quadrant. From the fitting results, both the reaction resistance R_ct and the inductance L decrease with the argument of RuO₂ content under bias potential of 600 mV, and in this case CO oxidation is the rate controlling step.     

Platinum nanoparticles ion-implanted-modified indium tin oxide electrode for electrocatalytic oxidation of formaldehyde

A facile and low-cost method is developed to ion implant platinum nanoparticles (PtNPs) onto indium tin oxide (ITO) electrode. This modified electrode is eco-friendly without the use of any linking chemicals. The PtNPs formed on the electrode are in the zero-valent metallic state with a size distribution in the range of 5–12 nm. The modified electrode surface becomes smoother after platinum ion implantation and the PtNPs formed on the electrode. Electrochemical performances are measured by cyclic voltammetry (CV) and chronoamperometric. The PtNPs/ITO electrode shows prominent electrocatalytic activity towards the oxidation of formaldehyde with long-term stability, which could be useful in fuel cells.