Carbon supported Pt hollow nanospheres as anode catalysts for direct borohydride-hydrogen peroxide fuel cells

The carbon supported Pt hollow nanospheres were prepared by employing cobalt nanoparticles as sacrificial templates at room temperature in aqueous solution and used as the anode electrocatalyst for direct borohydride-hydrogen peroxide fuel cell (DBHFC). The physical and electrochemical properties of the as-prepared electrocatalysts were investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), cyclic voltammetry (CV), chronoamperometry (CA), chronopotentiometry (CP) and fuel cell test. The results showed that the carbon supported Pt nanospheres were coreless and composed of discrete Pt nanoparticles with the crystallite size of about 2.8 nm. Besides, it has been found that the carbon supported Pt hollow nanospheres exhibited an enhanced electrocatalytic performance for BH₄⁻ oxidation compared with the carbon supported solid Pt nanoparticles, and the DBHFC using the carbon supported Pt hollow nanospheres as electrocatalyst showed as high as 54.53 mW cm⁻² power density at a discharge current density of 44.9 mA cm⁻².     

Preparation and characterization of nanoporous carbon-supported platinum as anode electrocatalyst for direct borohydride fuel cell

The nanoporous carbon (NPC) is synthesized by carbonization of metal–organic framework-5 (MOF-5, [Zn₄O(bdc)₃], bdc = 1,4-benzenedicarboxylate) with furfuryl alcohol (FA) as carbon source and used as the carrier of the anode catalyst for the direct borohydride–hydrogen peroxide fuel cell (DBHFC). Then the NPC-supported Pt anode catalyst (Pt/NPC) is firstly prepared by a modified NaBH₄ reduction method. The obtained Pt/NPC catalyst is characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive spectrometry (EDS), cyclic voltammetry, chronopotentiometry, chronoamperometry and fuel cell test. The results show that the Pt/NPC is made up of the spherical Pt nanoparticles which disperse uniformly on the surface of the NPC with average size 2.38 nm, and exhibits 36.38% higher current density for directly borohydride oxidation than the Vulcan XC-72 carbon supported Pt (Pt/XC-72). Besides, the DBHFC using the Pt/NPC as anode electrocatalyst shows the maximum power density as high as 54.34 mW cm⁻² at 25 °C.     

Preparation and electroactivity of polymer-functionalized graphene oxide-supported platinum nanoparticles catalysts

Polymer-functionalized graphene oxide or pristine graphene oxide supported platinum nanoparticles (Pt NPs) was prepared to study the surface modification effects. The catalysts were characterized by transmission electron microscopy, energy dispersive spectrometry, X-ray diffraction and thermogravimetric analysis. The electrochemical activities of Pt NPs were measured by cyclic voltammograms. The poly(diallyldimethylammonium chloride) (PDDA) was used as a modifier agent which formed a functionalized layer on graphene oxide (GO) sheets. As a result, the electrochemical active surface area (ESA) of PDDA functionalized GO supported Pt (Pt/PDDA–graphene) was shown to 66 m²/g that indicated higher hydrogen adsorption amount than 55 m²/g of the pristine Pt/graphene. In addition, an average particle size of Pt/PDDA–graphene NPs was measured to 1.8 nm slightly smaller than 2.0 nm of pristine Pt/graphene NPs.     

Addition of rhenium (Re) to Pt-Ru/f-MWCNT anode electrocatalysts for enhancement of ethanol electrooxidation in half cell and single direct ethanol fuel cell

Pt-Ru and Pt–Re and Pt-Ru-Re nanoparticles supported on functionalized multi-walled carbon nanotubes (f-MWCNT) were synthesized via modified polyol reduction method and tested thoroughly in a half cell and single direct ethanol fuel cell for ethanol electrooxidation in acidic medium. The MWCNTs were functionalized in a mixture of HNO₃/H₂SO₄ solution for depositing a more active metal alloy nanoparticle on support material. The alloy formation of bi-metallic and tri-metallic electrocatalysts were examined by XRD analysis and more clearly explained by FE-SEM element mapping. The TEM analyses reveal that electrocatalysts nanoparticles are well dispersed on f-MWCNT, with spherical shapes and nano sizes range of 1.5–4 nm. The electrochemical analyses by cyclic voltammetry and chronoamperometry measurements reveal that tri-metallic electrocatalyst Pt-Ru-Re (1:1:0.5)/f-MWCNT exhibits the highest electrocatalytic activity and stability towards ethanol electrooxidation among all the synthesized electrocatalysts. The same electrocatalyst as anode in single DEFC results in excellent performance in comparison to all other synthesized electrocatalysts, with a maximum power density of 9.52 mW/cm² at a cell temperature of 30 °C. The bi-metallic Pt-Ru (1:1)/f-MWCNT and Pt–Re (1:1)/f-MWCNT produced power density of 7.48 mW/cm² and 4.74 mW/cm² at room temperature of 30 °C. The power density of DEFC enhanced 2.44 times, when cell operating temperature was increased from 30 °C to 80 °C using anode electrocatalyst Pt-Ru-Re (1:1:0.5)/f-MWCNT and keeping other parameters constant. The best result obtained in half cell and single DEFC using Pt-Ru-Re (1:1:0.5)/f-MWCNT electrocatalyst may be attributed to the synergistic effect of Pt, Ru and Re combined with bi-functional and ligand effects.     

One-step fabrication of new generation graphene-based electrodes for polymer electrolyte membrane fuel cells by a novel electrophoretic deposition

High Pt loading has better tradeoff in polymer electrolyte membrane fuel cell (PEMFC) in terms of improved performance and operational longevity. But, to employ low amounts of Pt electrocatalysts via an alternative carbon-based support and utilization technique is vital. This study presents the use of a one-step novel technique, an electrophoretic deposition (EPD) method, through which reduced graphene oxide (rGO) supported Pt nanoparticles have been directly fabricated onto carbon paper to form electrodes for PEMFC. Our process involves simultaneous synthesis and deposition of Pt-reduced GO nanocomposites onto oxygen plasma pre-treated carbon paper in an organo-aqueous media at various deposition time. Through this technique, homogenously distributed Pt nanoparticles ranging from 5 to 6 nm in size on graphene support were successfully synthesized to form catalyst layer on carbon paper. The characteristics of fabricated electrodes were investigated ex-situ by Raman spectroscopy, FE-SEM, XPS, ICP, FIB, TEM. Furthermore, catalytic activity towards hydrogen oxidation reaction was evaluated via CV measurements and fuel cell performance tests were also conducted. The highest ECSA value of 27.4 m²g^-1 and the Pt utilization efficiency of 1.48 kW/g_Pt^?1 were achieved at an optimized Pt loading of 0.129 mg cm^?2. A maximum power density of 280 mW cm^?2 was obtained with increasing EPD time and Pt precursor concentration at the same time. The achieved results are attributed to the dispersion of Pt nanoparticles on rGO nanosheets displaying synergetic performance as catalyst necessary for PEMFCs, thanks to the EPD technique's viability, ease in handling, and reproducibility in the synthesis route. In the previous studies on Pt/GO based fuel cell electrodes by EPD, on one hand, Pt NPs were synthesized on GO by chemical methods first and electrodes were fabricated by a subsequent EPD. On the other hand, the fuel cell performances of those electrodes have been rarely shown. To the best of our knowledge, this is the first time in literature not only about the use of EPD technique for the fabrication of fuel cell electrodes in one-step but also the evaluation of fuel cell performance of the electrodes fabricated by EPD.     

Multi walled carbon nanotubes based micro direct ethanol fuel cell using printed circuit board technology

Multi walled carbon nanotubes (MWNTs) have been synthesized by chemical vapour deposition technique using AB₃ alloy hydride catalyst. Platinum supported MWNTs (Pt/MWNTs) and platinum-tin supported MWNTs (Pt–Sn/MWNTs) electrocatalysts have been prepared by chemical reduction method. MWNTs and electrocatalysts have been characterized by powder X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), high resolution TEM (HRTEM) and Energy dispersive X-ray analysis (EDAX). The anode and cathode electrodes for DEFC have been fabricated using Pt–Sn/MWNTs and 1:1 Pt/MWNTs + Pt/C electrocatalyst respectively. Performances of Direct Ethanol Fuel Cell (DEFC) with these electrodes have been studied at different temperatures of the membrane electrode assembly at ambient fuel conditions and the results have been discussed. A maximum power density of 38.6 mW/cm² at a current density of 130 mA/cm² is obtained. A six cell planar Micro Direct Ethanol Fuel Cell (μ-DEFC) stack was also constructed using these electrocatalysts and etched printed circuit boards as anode and cathode current collectors. A maximum power density of 2 mW/cm² was achieved when the μ-DEFC was operated in air breathing mode at room temperature. This enhancement of the performance may be attributed to dispersion and accessibility of MWNTs support and Pt–Sn in the electrocatalyst mixture for ethanol oxidation reaction.     

Novel anodes for fuel cell using nanostructured tungsten and titanium based electrocatalysts

Nano-structured Pt-WO₃/C, Pt-WO₃-TiO₂/C and Pt/C catalysts are synthesized by chemical reduction method using sodium borohydride as reducing agent. The catalysts thus prepared are characterized and compared with commercial Pt/C catalyst. The electrochemical performances are characterized by single cell test evaluation, long term stability test and cyclic voltammetry measurement. The chemical compositions, physical and morphological characterizations are investigated by various techniques such X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). XRD analysis shows that, all prepared catalysts exhibited face-centered cubic structures. XRD results confirm that, the Pt-WO₃/C and Pt-WO₃-TiO₂/C catalysts are smaller in particle size and larger in surface area calculated from line broadening. The amount of Pt reduced from1.76 mg cm⁻² (10% Pt/C) to 1.056 mg cm⁻² and 0.704 mg cm⁻² in the case of Pt-WO₃/C and Pt-WO₃-TiO₂/C respectively. Both the tungstate and titanate based electrocatalysts have exhibited higher performance in single cell tests than lone Pt catalysts.     

Chemically and thermally reduced graphene oxide supported Pt catalysts prepared by supercritical deposition

Reduced graphene oxide (RGO) is used in many energy applications, especially in Polymer Electrolyte Membrane (PEM) fuel cells, as carbon sourced catalyst support materials. In this study, thermally (T-RGO) and chemically (C-RGO) reduced GO support materials were synthesized for utilization in PEM fuel cells. Pt catalysts were synthesized using supercritical carbon dioxide (SCCO₂) deposition technique over synthesized support materials. Physical (BET, SEM-EDX, FTIR, RAMAN, XRD, TEM, ICP-MS and optical tensiometer) and electrochemical (CV, PEM fuel cell test) characterizations of synthesized support materials and corresponding Pt catalysts were performed. The differences between the structures of thermally and chemically reduced graphene oxide supports and their Pt catalysts were investigated. The ECSA values of the Pt/T-RGO and Pt/C-RGO catalysts are 19.86 m² g^?1 and 6.31 m² g^?1, respectively. The current and power density values of the Pt/T-RGO and Pt/C-RGO catalysts at 0.6 V are 84 mA cm^?2, 80 mA cm^?2 and 50 mW cm^?2, 45 mW cm^?2, respectively. Pt/T-RGO and Pt/C-RGO catalysts showed similar trend in PEMFC environment.     

The performance and degradation of Pt electrocatalysts on novel carbon carriers for PEMFC applications

Electrocatalyst stability is an important factor influencing the performance of polymer electrolyte membrane (PEM) fuel cells and is essential in maintaining the cell output. The aim of this work was to elucidate factors which influence the stability of platinum supported onto graphitic nanofibres (Pt/GNFs) and to compare the performance of these materials with the commonly used Pt/Vulcan electrocatalyst. Platinum nanoparticles (average diameter of 6.9 nm) were supported on GNFs which were prepared by chemical vapour deposition over an unsupported nickel oxide (NiO) catalyst precursor. The performance of Pt/GNFs based electrodes were studied by cyclic voltammetry and a single-cell fuel cell test and were compared with a commercially available carbon nanostructure, Vulcan XC-72, which was also impregnated with Pt nanoparticles. Characterisation of the pre- and post-operation of the Pt/GNFs by XRD and TEM showed that structural changes of the Pt had occurred during testing. It was found that the average diameter of each grain and the degree of agglomeration among particles was increased, creating elongated clusters of Pt along the carbon fibre. Analysis of electrocatalyst post-operation also identified that the sulphate from the Nafion membrane was reacting with the Pt surface forming platinum sulphide (PtS). These phases were confirmed by the presence of low intensity, but sharp XRD peaks, attributed to a few large diameter particles (49 nm). These two factors resulted in current density dropping from 0.2 A/cm² to 0.1 A/cm² (at 0.70 V) over a 25 h test period.     

Efficient electro-oxidation of methanol using PtCo nanocatalysts supported reduced graphene oxide matrix as anode for DMFC

Platinum – cobalt (PtCo) alloy based highly efficient nano electro-catalysts on reduced graphene oxide (rGO) matrix have been synthesized for the electro-oxidation of methanol, by chemical reduction method. Different molar ratio of Pt (IV) and Co (II) ions along with graphene oxide (GO) were reduced using ethylene glycol to obtain PtCo nanoparticles onto rGO sheets (Pt/rGO, PtCo (1:1)/rGO, PtCo (1:5)/rGO, PtCo (1:9)/rGO and PtCo (1:11)/rGO) with 20 wt. % metal and 80 wt. % rGO. The average particle size of PtCo nanoparticles onto rGO support was observed to be 2–5 nm using XRD and TEM analysis. The PtCo (1:9)/rGO nanocomposite catalyst exhibited ～23 times higher anodic current density compare to commercially available Pt/C catalyst (1.68 mA/cm²) for methanol oxidation reaction. The peak power density of 118.4 mW/cm² was obtained for PtCo (1:9)/rGO catalyst in direct methanol fuel cell (DMFC) at 100 °C, 1 bar, and 2 M methanol as anode feed, which is ～3 times higher than that of Pt/C catalyst. The results indicate the potential application of synthesized nanocomposite catalyst in commercial DMFCs.     

Preparation of PEDOT-modified double-layered hollow carbon spheres as Pt catalyst support for methanol oxidation

In this paper, Pt nanoparticles (Pt NPs) deposited hybrid carbon support is prepared by modifying double-layered hollow carbon spheres（DLHCs）with poly(3,4-ethylenedioxythiophene) (PEDOT) and used as anode catalyst of methanol oxidation. The structure of nanocomposites is characterized by SEM, TEM, FT-IR, XRD and XPS, confirming the greatly enhanced synergistic effect between the PEDOT and DLHCs, and illustrating the uniform distribution of Pt NPs on the PEDOT/DLHCs composite surface with a small particle size (~2.63 nm). Cyclic voltammetry, chronoamperometry and impedance spectroscopy applied to determine the electrocatalytic activity of catalysts, it is found that the synthesized PEDOT/DLHCs/Pt possesses excellent characteristics such as large electrochemically active surface area and high mass activity of 59.45 m² g⁻¹ and 807 mA mg⁻¹ in 0.5 M H₂SO₄ containing 1 M methanol solution, which is almost 1.24 and 2.8 times greater than those of commercial Pt/C, and the catalyst exhibits superior stability after 500 durability cycles. The enhanced electrocatalytic behavior can be ascribed to the excellent electronic conductivity of PEDOT-modified DLHCs and the strong binding of PEDOT/DLHCs to Pt NPs, suggesting that the PEDOT/DLHCs/Pt is a promising electrocatalyst for direct methanol fuel cell.     

CVD graphene supported cobalt (II) phthalocyanine as cathode electrocatalyst for PEM fuel cells

For the first time, CVD graphene supported cobalt (II) phthalocyanine (CoPc) is investigated as a possible catalyst to replace Pt cathode in polymer electrolyte membrane (PEM) fuel cells. Impregnation method is utilized for the synthesis of CVD graphene supported CoPc catalyst. Higher heat-treatment temperatures for CoPc/CVD graphene mixtures have resulted with better electrochemical activity and stability. 5% Co/CoPc-G electrode compare to 9.3% Co/CoPc-G for 0.3 mg Co/cm² loading has resulted reduced voltage-current characteristics due to kinetic and mass transfer limitations. Operational parameters are evaluated resulting maximum power density of 186 mW/cm² with 9.3Co%/CoPc-Graphene, 25-psi backpressure, 100% RH and 80 °C operational temperature.     

Hydrothermal synthesis of Pt/MWCNTs nanocomposite electrocatalysts for proton exchange membrane fuel cell systems

A hydrothermal method for preparation of size-controlled Pt nanoparticles dispersed highly on multiwalled carbon nanotubes (Pt/MWCNTs) has been studied to optimize the effective parameters (temperature, time, pH and stirring rate) using Taguchi method. The synthesized Pt/MWCNTs nanocomposite samples were characterized through X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray fluorescence (XRF) analyses to identify mean Pt nanoparticles size and Pt content. The analysis of the primary experimental data and demonstration of the main effect trend of each parameter showed that a reaction temperature of about 140 °C, a reaction period of 5 h, a slightly basic reaction pH (∼9) and a stirring rate of 500 rpm are the optimum process conditions which give a low mean Pt nanoparticles size (2.8 nm) and a high Pt content (19.4 wt.%) simultaneously. Cyclic voltammetry (CV) analysis showed that under optimum conditions the synthesized sample gives a specific surface area of 99 m² g⁻¹. Obtaining the polarization curves for the two fabricated membrane electrode assemblies (MEAs) using the optimized catalyst and a commercial Pt/C catalyst (10 wt.%, Aldrich) with Pt loading of 0.4 mg cm⁻² demonstrated that the catalyst prepared under optimum conditions shows a considerably better performance.     

PtCo/N-doped carbon sheets derived from a simple pyrolysis of graphene oxide/ZIF-67/H2PtCl6 composites as an efficient catalyst for methanol electro-oxidation

Many alloy catalysts have been developed for methanol electro-oxidation, but most synthetic methods are complicated. Herein, PtCo alloy catalysts supported on N-doped carbon sheets (PtCo/NCS) are successfully prepared by a simple pyrolysis of graphene oxide/ZIF-67/H₂PtCl₆ composites at different temperatures (700, 800, 900 °C) under a gas flow of H₂/Ar, in which ZIF-67 is served as Co and N sources. SEM, TEM, XRD, XPS and electrochemical characterization are employed to study as-prepared catalysts. In acidic methanol solution, the area-specific activity (1.25 mA cm⁻² Pt) of PtCo alloy catalyst obtained at 800 °C (PtCo/NCS-800) is 2.6 times of commercial Pt/C (0.48 mA cm⁻² Pt), and the area-specific activity of PtCo/NCS-800 is 3.5 times of Pt/C after 1000 cycles. Furthermore, an improved CO-tolerance of Pt is confirmed. The electronic effect and synergistic effect of metallic elements are responsible for outstanding performance of as-prepared catalysts. This work provides a simple approach to obtain high performance alloy catalysts.     

Synthesis and characterization of Pt-Au/C catalyst for glucose electro-oxidation for the application in direct glucose fuel cell

To minimize the poisoning of Pt-catalyst in glucose electro-oxidation for direct glucose fuel cell, carbon supported low metal loaded platinum-gold (Pt-Au/C) catalyst (1:1) was synthesized by immobilizing metal sols on carbon. The physical characterization of Pt-Au/C, Pt/C and Au/C was carried out using transmission electron microscope (TEM), scanning electron microscope (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD) and thermo gravimetric analysis (TGA). SEM indicates the uniformity in loading of metals on Vulcan XC-72 carbon support, whereas TEM picture and XRD pattern confirm the formation of Pt-Au nanoparticles of less than 10 nm size. TGA shows the metal present in Pt-Au/C catalyst is 14.5% by wt. Electrochemical analysis such as cyclic voltammetry (CV) and chronoamperometry (CA) on Pt-Au/C and commercial Pt/C and Au/C (40 wt. % of metal) for glucose electro-oxidation in alkaline media shows that Pt-Au/C is capable of electro-oxidation of glucose at low potential as that of Pt/C catalyst and more active than Au/C catalyst. The poisoning rate of prepared Pt-Au/C (0.0046% s⁻¹) is lower than that of Pt-Ru/C (0.0085% s⁻¹) and Pt/C (0.011% s⁻¹) catalysts. A batch cell operated using Pt-Au/C as anode and activated charcoal as cathode delivered 0.9 V OCV and 0.72 mW cm⁻² peak power density at 0.2 M glucose in 1 M KOH solution.     

Sm2O3 promoted Pd/rGO electrocatalyst for formic acid oxidation

Herein, we report the synthesis of Sm₂O₃ incorporated palladium based electrocatalyst, supported over reduced graphene oxide (rGO). Pd_xSm_y nanoparticles (20 wt %) are distributed over rGO surface by using sodium borohydride reduction technique. Different physicochemical analyses are used to characterize the Pd_xSm_y/rGO electro-catalysts (x = 2,4,6 and y = 8,6,4). The synthesized materials (Pd_xSm_y/rGOs) are investigated for their catalytic capabilities toward electro-oxidation of formic acid. The results show that adding Sm₂O₃ to the Pd/rGO electrocatalyst boosts electrochemical activities of the materials toward formic acid oxidation. The optimized catalyst (Pd₆Sm₄/rGO) shows excellent activity towards formic acid oxidation with current density of 46.70 mA/cm² compared to reference catalysts i.e., Pd/rGO (28.78 mA/cm²) and Pd/C (22.22 mA/cm²). The optimized catalyst also demonstrates high CO tolerance and great stability during formic acid oxidation reaction. The enhanced activity and stability are attributed to the synergistic interaction between Sm₂O_3, and palladium nanoparticles supported over reduced graphene oxide.     

Synthesis,characterization and 1-propanol electrooxidation application of carbon nanotube supported bimetallic catalysts

In this study, 1-propanol electrooxidation activities of Pt and Bi catalysts synthesized by NaBH₄ co-reduction and sequential reduction methods are compared. The characterization of the catalysts supported carbon nanotube (CNT) is determined by XRD, SEM-EDX, TEM, and ICP-MS analyzes. In the TEM results, it is seen that Pt and Bi metal nanoparticles are dispersed into carbon nanotubes. Electrochemical measurements of CV, CA, and EIS are applied to investigate the catalytic activities of catalysts for 1-propanol electrooxidation. Bi@Pt/CNT catalyst exhibits the highest catalytic activity (24.212 mA/cm² and 1950.06 mA/mg Pt), long-term stability and lowest resistance. As a result, it was concluded that the catalyst activity increased with the sequential reduction method and the Bi@Pt/CNT catalyst was promising with its high activity value for direct alcohol fuel cells.     

Investigation of the effect of graphitized carbon nanotube catalyst support for high temperature PEM fuel cells

In this study, it is aimed to investigate the graphitization effect on the performance of the multi walled carbon nanotube catalyst support for high temperature proton exchange membrane fuel cell (HT-PEMFC) application. Microwave synthesis method was selected to load Pt nanoparticles on both CNT materials. Prepared catalyst was analyzed thermal analysis (TGA), Transmission Electron Microscopy (TEM) and corrosion tests. TEM analysis proved that a distribution of Pt nanoparticles with a size range of 2.8–3.1 nm was loaded on the Pt/CNT and Pt/GCNT catalysts. Gas diffusion electrodes (GDE) were manufactured by an ultrasonic spray method with synthesized catalyst. Polybenzimidazole (PBI) membrane based Membrane Electrode Assembly (MEA) was prepared for observe the performance of the prepared catalysts. The synthesized catalysts were also tested in a HT-PEMFC environment with a 5 cm² active area at 160 °C without humidification. This study demonstrates the feasibility of using the microwave synthesis method as a fast and effective method for preparing high performance Pt/CNT and Pt/GCNT catalyst for HT-PEMFC. The HT-PEMFC performance evaluation shows current densities of 0.36 A/cm²0.30 A/cm² and 0.20 A/cm² for the MEAs prepared with Pt/GCNT, Pt/CNT and Pt/C catalysts @ 0.6 V operating voltage, respectively. AST (Accelerated Stress Test) analyzes of MEAs prepared with Pt/GCNT and Pt/CNT catalysts were also performed and compared with Pt/C catalyst. According to current density @ 0.6 V after 10,000 potential cycles, Pt/GCNT, Pt/CNT and Pt/C catalysts can retain 61%, 67% and 60% of their performance, respectively.     

Preparation and characterization of Pt nanoparticles supported on modified graphite nanoplatelet using solution blending method

Platinum nanoparticles have been successfully assembled on polyaniline functionalized graphite nanoplatelet (GNP) via a noncovalent functionalization strategy. The characterization of obtained nanocomposite was investigated by XRD, TEM, XPS and electrochemical technology. When the moderate amount of polyaniline as a stabilizer, Pt nanoparticles with sizes of approximate 4–5 nm uniformly disperse on GNP surface. In methanol oxidation reaction, the electrocatalytic activity of Pt/PANI-GNP is nearly 2 times higher than that of Pt/GNP catalyst. Through analysis, it is suggested that the electrocatalysis performance of Pt/PANI-GNP may be improved by the following four factors: (1) uniformly distributed nanoparticle; (2) increased of amount of Pt⁰ and oxygen-containing groups; (3) the existence of N atoms; (4) difference reaction mechanism.     

Pt and Pt–Ag nanoparticles supported on carbon nanotubes (CNT) for oxygen reduction reaction in alkaline medium

In this work, we investigated the effect of the carbon nanotubes (CNT) as alternative support of cathodes for oxygen reduction reaction (ORR) in alkaline medium. The Pt and Pt–Ag nanomaterials supported on CNT were synthesized by sonochemical method. The crystalline structure, morphology, particle size, dispersion, specific surface area, and composition were investigated by XRD, SEM-EDS, TEM, HR-TEM, N₂ adsorption-desorption and XPS characterization. The electrochemical activity for ORR was evaluated by cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS) in alkaline medium. The electrochemical stability was researched by an accelerated degradation test (ADT). Pt/CNT showed the better electrocatalytic activity towards ORR compared with Pt–Ag/CNT and Pt/C. Pt/CNT exhibited higher specific activity (1.12 mA cm^?2 _Pt) than Pt/C (0.25 mA cm^?2 _Pt) which can be attributed to smaller particle size, Pt-CNT interaction, and Pt load (5 wt%). The Pt monometallic samples supported on CNT and Vulcan showed higher electrochemical stability after ADT than Pt–Ag bimetallic. The ORR activity of all materials synthesized proceeded through a four-electron pathway. Furthermore, the EIS results showed that Pt/CNT exhibited the lower resistance to the transfer electron compared with conventional Pt/C and Pt–Ag/CNT.