Research efforts direct ethanol fuel cell defc


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Research efforts direct ethanol fuel cell defc

  1. 1. © 2012 American Chemical Society - | ACS Catal. 2012, 2, 287− 297 Palladium − Tin Alloyed Catalysts for the Ethanol Oxidation Reaction in an Alkaline Medium By: A.M,Sheikh LAPEC (Corrosion Research Laboratory) – UFRGS – Brazil
  2. 2. The Objective7/26/2012 To formulate the Pd-Sn/C binary alloyed catalyst for EOR to determine its activity towards ethanol electrooxidation in alkaline medium 2
  3. 3. Experimental, Pd-Sn/catlysts synthesis• Pd-Sn/C catalysts were synthesised by the modified polyol method followed by supporting carbon black (Vulcan XC72R).• (33.3 mg SnCl2+12 mL Ethylene Glycol (EG)+1 mL DI water) heating 80C+1 hr reac.• 26 mg of K 2 PdCl4+3 mL of EG+ 8 mL of pre- heated EG 130C + 0.02mmol Sn solution• 30 min reaction + argon flow+ C black
  4. 4. Experimental- charachterization• The high-angle annular dark field HAADF- TEM, & electron energy loss spectroscopy (EELS)• XRD Bruker AXS instrument equipped with a GADDS (GeneralArea Detector Diffraction System) detector• Chemical compositions;Pd-Sn:PGT Imix-PC energy dispersive X-ray spectroscopy (EDS)
  5. 5. Electrochemical Measurements• Using 3-electrode cell; GCE working electrod, platinum wire counter electrode & Hg/HgO (1 M KOH) reference electrode• Nafion working solution:Nafion 117 ∼ 5 wt% mixed of lower aliphatic alcohols and water• DFT Calculations: by dual basis set, using the Gaussian and plane waves (GPW) method.
  6. 6. Conclusion• C supported Pd−Sn nanoparticles via a polyol method• Pd−Sn/C catalysts: two times higher peak current densities than Pd/C in CV measures• Sn content charge transfer rate during EOR• EOR on Pd−Sn catalysts partial oxidation of ethanol forming acetic acid• Future: complete:EOR DFT calculation Pd−Sn (facile synthetic route& enhancing EOR
  7. 7. international journal of hydrogenenergy36(2011)9994-9999 Performance of an alkaline-acid direct ethanol fuel cell By: A.M.Sheikh LAPEC (Corrosion Research Laboratory) – UFRGS
  8. 8. Electrochimica Acta 55 (2010) 3002–3007Carbon supported Pd–Co–Mo alloy as analternative to Pt for oxygen reduction in direct ethanol fuel cells By: A.M.Sheikh LAPEC (Corrosion Research Laboratory) – UFRGS
  9. 9. Journal of Power Sources 190 (2009) 241–251 Pd and Pt–Ru anode electrocatalysts supported onmulti-walled carbon nanotubes (MWCNTs) and theiruse in passive and active direct alcohol fuel cells with an anion-exchange membrane (alcohol = methanol, ethanol, glycerol) By: A.M.Sheikh LAPEC (Corrosion Research Laboratory) – UFRGS
  10. 10. Experimental-Materials analysis & Catalyst preparation• MWCNTs: by CVD & treated with H2SO4 50% (v:v) for 14 h & (HNO3 65%, 120◦C, 8 h)• MWCNTs Pd & Pt-Ru: [Pt(CH3)2(COD)], [Ru (COD)(COT)], [Pd2(dba)3]• Pd/MWCNT: 1gm MWCNT+ 50ml THF+ sloution [Pd2(dba)3] (.25gm) in 50 ml THF• Pt-Ru/MWCNT: 65ml toluene aerated with argon+2gm MWCNT,1hr sonication+ 1gm [Ru (COD)(COT)] + 0.7gm [Pt(CH3)2(COD)]
  11. 11. Experimental- Active & Passive DAFCs Active DAFC with Au-The home-made DAFC: toevaluate the performance plated current collectorsof Pd/MWCNT anodes, and Ti end plates forpassive DAFC alkaline purpose A dense anode ink was prepared by mixing the powdered catalyst with a 5– 10 wt.% aqueous dispersion of PTFE.
  12. 12. 7/26/201212
  13. 13. 7/26/201213
  14. 14. 7/26/2012 Polarization and power density curves at different temperatures of active DAFC with a Pd/MWCNT anode (metal loading 1 mg cm−2 ), fuelled with an aque- ous 2 M KOH solution of (A) methanol (10 wt.%); (B) ethanol (10 wt.%); (C) glycerol (5 wt.%). Inset report the temperatures of fuel (left), cell (central), oxygen gas (right). 14
  15. 15. Conclusion• The MWCNT-supported Pd nanoparticles are effective catalysts for alcohol oxidation DAFC• (MEA) containing a Pd/MWCNT anode,Fe-Co Hypermec™ cathode &Tokuyama A-006 AEM provided excelent results• Ethanol: oxidized on Pd/MWCNT to acetic acid, to acetate ion in the alkaline media.• DMFC: Pd/MWCNT is more active than Pt- Ru/MWCNT
  16. 16. S.Y. Shen et al. / Electrochimica Acta 55 (2010) 9179–9184Carbon-supported bimetallic PdIrcatalysts for ethanol oxidation in alkaline media By: A.M.Sheikh LAPEC (Corrosion Research Laboratory) – UFRGS
  17. 17. Literature review• Non-noble metal catalyst is na advantage of AEM in alkaline media EOR in DAFCs• Ethanol as alcohol: high energy density, less toxic, can be transported in large quantities.• Pd has bothe higher activity for EOR and steady state behavior in alkaline media than Pt.• Pd: alloyed (Au, Sn, Ru, Ag, Ni, Pb or Cu)• This work: to have PdIr/C by simultanous red.
  18. 18. Experimental- Catalyst synthesis• All chemicals in DI water• PdCl2, H2IrCl6, K3C6H5O7, NaBH4, KOH, HCl, & ethanol (CH3CH2OH) were used.• Catalysts sythesised by simultaneous reduction method using cericate as complexing agent and stabilizer• Dissolution in DI water+ K3C6H5O7 + suspending Cpowder+ filteration+drying Pd/C ci-Pd/C catalysts
  19. 19. Experimental- Physicochemical, electrochemical characterizations• XRD (scan rate of 0.025◦/s)• TEM at 200 kV• XPS Al monochromatic X-ray at a power of 350 W• CV, LSV and CP: conventional 3-electrode cell: (GCE) of 0.1256 cm2-working, Pt foil-counter, and Hg/HgO/KOH (1.0 mol dm−3) (MMO, 0.098 V vs. SHE)-reference.
  20. 20. Conclusion• Carbon supported bimetalic PdIr catalysts by reduction method using NaBH4 as reductant and citrate as complexing agent.• The onset potential of PdIr7/C is much more negative than Pd/C• Addition of Ir can remove adsorbed ethoxi species.
  21. 21. M.C. Oliveira et al. / Journal of Power Sources 196 (2011) 6092–6098 Evaluation of the catalytic activity ofPd–Ag alloys on ethanol oxidation andoxygen reduction reactions in alkaline medium By: A.M.Sheikh LAPEC (Corrosion Research Laboratory) – UFRGS
  22. 22. Letrature review• Most polymer membrane reaseach efforts were considering exclusively the acid media.• The reaction kinetics in alkaline media are higher than that in acid media.• Pd and Pd alloys have shown higher activity for ORR an EOR for DAFCs specially in alkaline media than traditional Pt alloys.
  23. 23. Objective• In this work, Pd–Ag alloys containing different amounts of Ag were prepared and their intrinsic catalytic activities towards EOR and ORR in alkaline media
  24. 24. Experimental- Preparation of Pd–AgPreparation of Pd–Ag films (oxide filmintermetalic barrier), supstrates dippingin SnCl2 & PdCl2 with de-ionizedwater to seed stainless steel withcatalytc nucleous.
  25. 25. Experimental- Preparation of Pd–Ag• Ag deposited at 60C and Pd at room temp.• Both Pd &Ag deposisted in 10 ml plating solution• Rinsing (deionized water) & drying at 40C- 24h• Annealing in argon atmosphere at 650C-6h
  26. 26. Exp. Pd-Ag films charchterization• XRD• SEM/EDS• EOR study (scan rate 20mV/s in NAOH + ETOH 1.0 M)• ORR study (scan rate 5mV/s in O2 staurated NaOH solution 1.0 M• Stainless steed coated with Pd-Ag film (0.169 cm2): used as electrode
  27. 27. Conclusion• Pd-Ag alloys synthesised by electroless deposition on stainless steel supstrate.• Pd-Ag alloys: better activity for EOR than Pd the highest active alloy is 21%Ag• Pd-Ag alloys have better activity for ORR than Pd at room temp.; the highest alloys is 8%Ag• Future: preparation of Pd-Ag as nanomaterial dispersed on carbon substrate.
  28. 28. international journal of hydrogen energy 36(2011)12686e12697 Pd-Ni electrocatalysts for efficient ethanol oxidation reaction in alkaline electrolyte By: A.M.Sheikh LAPEC (Corrosion Research Laboratory) – UFRGS
  29. 29. Literature review• Production, storage, & transport of hydrogen for PEMFC and Ethanol is alternative• DEFC: ideal electrochemical device (without carnot cycle limitations)• Reported that PtSN catalysts than Pt-metal• DEFC AEM & high effeciency (improved kinetics, enhanced life time, reduced cost)• Pd can break C-C in high pH media.
  30. 30. Objective• Elegant organic sythesis solution for control of nanoparticles thickness• In this work, is saught to develop carbon support Pd-Ni with different compositions• Catalysts have 3nm distributions• The correlation between enhanced EOR and the Pd-Ni composition and structure.
  31. 31. ExperimentalPd/C, PdxNiy/C, and Pd1 Ni1 /CeNaBH4catalysts preparation Procedures of nanocapsule synthesis method for preparing Pd1- Ni1 /C catalyst
  32. 32. Charachterization• XRD• TEM• HR-TEM• Energy Dispersive X-ray spectroscopy (EDS)• Inductively coupled plasma atomic emission spectroscopy (ICP-AES)• Thermogravimetric analysis (TGA)
  33. 33. Tests• cyclic voltammetry (CV)• Linear scan voltammetry (LSV)• chronoamperometry (CA)• All potentials: vs. Hg/HgO (1.0 M NaOH) electrode (0.140 V vs. NHE)• First, (1.0mg catlyast+1.0ml ethanol) ultrasonically- treated 5 min.• Electrode: dropping 20 ml on GCE (covered .05% TPQPOH solution
  34. 34. Conclusion• A solution phase-based nanocapsule method: PdxNiy/C catalysts, diameters (2.4-3.2nm), size distributions (1-6nm) & surface areas (i.e. 68.0 m/g for Pd2Ni1/C)• PdxNiy/C catalysts in alkaline medium: higher activity towards EOR &’detoxification’ ability• Ni could promote refreshing Pd active sites• Nanocapsule method: efficient Pd&Ni contacts
  35. 35. Electrochimica Acta 75 (2012) 191–200 Co-deposition of Pt and ceria anode catalyst in supercritical carbon dioxidefor direct methanol fuel cell applications By: A.M.Sheikh LAPEC (Corrosion Research Laboratory) – UFRGS
  36. 36. international journal of hydrogen energy 37(2012)9314-9323 Effect of decreasing platinum content amount in Pt-Sn-Ni alloys support as electrocatalyst for ethanol electrooxidation Patrı´cia dos Santos Correa.a,*, Elen Leal da Silva.a, Renato Figueira da Silva.b,Cla´udio Radtke.c, Berta Moreno.d, Eva Chinarro.d, Ce´lia de Fraga Malfatti By: A.M.Sheikh LAPEC (Corrosion Research Laboratory) – UFRGS
  37. 37. Letrature review• Pt is the most favorable catalyst metal.• Methanol is toxic.• Ethanol is considered good alternative in low temperature.• Ethanol oxidation is complex and slow.• Pt/C is most comum, but it is poisoned rapidly (CO catalyst)• The presence of Sn2O3 is favored and Si causes dilatation of crystal lattic.
  38. 38. The work objective• The use of impregnation/reduction method• Ethyln glycol is the reducing agent.• Using ctalayst alloys of PtNiSn/C• Mesuring the effect of the composition on the electrochemical behavior.
  39. 39. Experimental-Electrocatalysts preparation1. PtSnNi/C Impregnation/Reduction2. Ethylene glycol Reducing agent3. Solution of H2 PtCl6.6H2O, SnCl 2.2H2O and NiCl2 (with 40% metal) in ethylene glycol and water (75/25 v/v)4. Adding carbon and agitation in ultrasonic bath dissolution of salts.5. Pure Pt, and Pt –Sn alloys were used to compare.6. The PH is 12 and T is 130 C7. Samples centrifugation and drying8. Analyses of the results RBS, XRD, TEM
  40. 40. Experimental- Electrochemical characterization• To determine the catalysts behavior in 1.0 M ethanol and 0.5 M H2 SO4 solution (25 C, 10 min).• Cyclic voltammetries CVs (PAR 273, scan rate of 50 mV/s+ 0.04 to 0.96 V potential range related to saturated calomelan electrode (SCE)• Electrochemical impedance spectroscopy measurements were performed in potentiostatic mode at 750 mV vs SCE (Solartorn SI 1255 coupled to a potentiostat Omnimetra PG-05).
  41. 41. Results analysis Diffractogram of the Pt-Sn-Ni/C (4 and 5) and Pt/C-home made electrocatalysts. (*)Unknown peaks.
  42. 42. Images obtainedfrom TEM (a)PtSnNi/C - A and(b) PtSnNi/C - Band distributionparticle size (c)and (d) of therespectiveelectrocatalysts.
  43. 43. CVs obtained in a 0.5 M H2 SO4 and 1.0 M ethanol solution (scan rate of 50 mV/s)ofthe: (a) PtSnNi/C - A, PtSnNi/C - B and Pt/C and (b) PtSn/C -C and PtSn/C - Delectrocatalysts.
  44. 44. Conclusion• RBS results: impregnation/reduction process Pt- Sn-Ni alloy particles with a composition control.• XRD: Pt fcc structure• The onset voltage for ethanol oxidation and the current density with adding Sn & Ni to Pt.• Decrease in Pt/Sn ratio: detrimental to catalytic activity toward ethanol electrooxidation• Adding Ni leads to decrease of charge transfer resistence
  45. 45. Received: 17 February 2012 /Revised: 26 April 2012 /Accepted: 17 May 2012 # Springer-Verlag2012 Preparation of PtSnRh/C-Sb2O5·SnO2 electrocatalysts by an alcohol reduction process for direct ethanol fuel cell J. C. Castro & R. M. Antoniassi & R. R. Dias & M. Linardi & E. V. Spinacé & A. Oliveira Neto By: A.M.Sheikh LAPEC (Corrosion Research Laboratory) – UFRGS
  46. 46. Literature review• The attention for new DEFC catalysts• (Pt + Co catalyst) is the most comum.• PtSN is a very good but acetaldhyde& acidic acid are produced.• Adding Rh to PtSn DEFC Co2• Another: to deposit Pt,Sn,&Rh nanoparticles on metal oxides CeO2,RuO2, SnO2• Pt nanoparticles supported on C &/or ATO
  47. 47. Objective• To prepare PtSnRh/C-Sb2O5·SnO2 with different atomic ratios• Using the alcohol reduction process to study the catalysts effect on ethanol electrooxidation• Comparing the results of PtSnRh/C- Sb2O5·SnO2 with those of PtSnRh/C (the reported most active ternary catalyst.
  48. 48. Experimental• Electrocatalysts PtSnRh/C-Sb2O5·SnO2 : prpared from H2PtCl6·6H2O, SnCl2·2H2O, & RhCl3·xH2O as metal sources in one step,• Pt/Sn/Rh (90:05:05, 70:25:05, & 50:45:05)• Ethylene glycol as solvent and reducing agent,• physical mixture of Vulcan XC72 (85 wt%) and Sb2O5·SnO2 (15 wt%) as supports.• XRD for PtSnRh/C & PtSnRh/C-Sb2O5·SnO2.• TEM, CV & CA were also carried out.
  49. 49. Experimental• DEFC tests: anode PtSnRh/C-Sb2O5·SnO2 & cathode Pt/C in single cell (A= 5 cm2)• DEFC; carbon closth as GDL & Nafion® 117 membrane as electrolyte• Electrodes: hot pressed on both sides of membrane at 100C, 2 min, 225GPa• Pt/cm2 of electrode is 1 mg, T(O2 humidifier)= 80 °C, O2 flow 500 mL/min, & 2 bar
  50. 50. Conclusion• Alcohol reduction: producing in a single step of PtSnRh/C-Sb2O5·SnO2 for ethanol oxidation.• Structure fcc for Pt & Pt alloys.• Nanoparticle size distribution 2-3 nm.• PtSnRh/C-Sb2O5·SnO2 (90:05:05) & PtSnRh/C- Sb2O5·SnO2 (70:25:05): exhibited higher performance than PtSnRh/C.
  51. 51. international journal of hydrogen energy36(2011)849-856 Electrolless Ni-B supported on carbon for direct alcohol fuel cell applications. H.B. Hassan, Z. Abdel Hamid By: A.M.Sheikh LAPEC (Corrosion Research Laboratory) – UFRGS
  52. 52. Letrature review• In this paper, the previous research efforts about Ni-B coatings for different uses. One of them is the electroless. Refs [1-10]• The srtucture of Ni-B coatings depends on the B content; <0.8 NANOcrystalline and >=20% AMOrphous.• The AMOrphous alloys have excellent catalytic properities, so they are used in hydrotreating operation.
  53. 53. The work objectiveThis work aims to investigate thecatalytic activitiy of Ni-B coatingssupported on comercial electrodesusing electroless technique and havecome from acidic path towards theelectrooxidation of some alcohols(ethanol and methanol.
  54. 54. The experimental preparartion• The Dimethyle Amine Borone (DMAB) was used as a reduceing agent.• The acidic plating path was 5 g/l Nicl2.6H2O, 7 g/l NaC 2 H 3 O 2 2 O, 7 g NaC 2 H 3 O 2 , 1.0 g/l (DMAB)• Operation conditions are PH 4, &T 60C.
  55. 55. Electrode preparation1. Mechanical polishing2. Degreased with acitone3. Rinsed with distilled water, and4. Dried with soft paperThree different NieB/C samples (I, II and III)were prepared at different deposition time of30, 60 and 120 min, respectively.
  56. 56. Electrical measurements preparation• The electrochemical measurements were performed using an Amel 5000 system (supplied by Amel instrument, Italy) driven by a PC for data processing.• The phase structure of the coatings was studied using XRD and The surface morphology was observed using SEM.• the boron content was determined using inductively coupled plasma-mass spectrometer (ICP-MS)
  57. 57. Results and Discussion• The Ni-B coating deposites decrease with the deposition time.• The coatings are uniform and they consist of agglomerates of nickel that are randomly distributed, these agglomerates slightly increase as the deposition time increases.• the material is microcrystalline nickel that considered as amorphous
  58. 58. Received: 12 January 2012 / Accepted: 10 May 2012v Springer Science + Business Media B.V. 2012 Platinum nanocatalysts prepared with different surfactants for C1–C3 alcohol oxidations and their surface morphologies by AFMSalih Ertan,Fatih S¸em,Selda S¸em,Gu¨lsu¨n Go¨kag˘ac By: A.M.Sheikh LAPEC (Corrosion Research Laboratory) – UFRGS
  59. 59. Lterature review• Metal nanoparticles (MNPs): used in catalytic reactions due to larger surface area than bulk• Surfactants: to prepare surfactant-stabilized PtNPs• MNPs: oxidation of alcohol to CO2 (DAFC)• DMFC & DEFC are the comum examples• Methanol: toxic & Ethanol: CO catalyst req.• Longer chain alcohols (2-propanol): energy density
  60. 60. Objective• Pt : the most active electrocatalyst• To produce PtNPs using PtCl4(starting)+ surfcants (1-octanethiol,1-decanethiol,1-dodecanethiol, &1- hexadecanethiol)• These catalysts: to determine surfactants chain length on alcohol oxidation.• XRD, XPS, AFM, CV, & CA were carried out on the catalyst samples.
  61. 61. Experimental• Catalyst is prepared by staring material PtCl4.• Catalysts I,II,III, and IV were prepared by super hydreide/reduction method (Ki-Sub et al. 2004; Sen et al. 2011)
  62. 62. Ctalayst preparation• PtCl4 (99 %) was obtained from Alfa, tetrahydrofuran (THF) (99.5 %)• Methanol (C99.5 %), ethanol (99.9 %), 2-propanol (C99.5 %) and HClO4 (60 %) were purchased from Merck.• Lithium triethylborohydride (superhydride) (1.0 M dissolved in THF)• 1-octanethiol, 1-decanethiol, 1-dodecanethiol and1-hexadecanethiol, were bought from Sigma-Aldrich,• Carbon XC-72 was acquired from Cabot Europa Ltd.• All chemical reagents in this study were of analytical grade purity.
  63. 63. superhydride/reduction method• 0.25 mmol (0.0808 g) of PtCl4 was completely dissolved in small amount of anhydrous THF• 0.25 mmol of surfactants was added to this solution.• Finally, superhydride and ethanol were added to reduce the thiol-stabilized platinum complex up to the observation of a brown color in the solution• dry ethanol was used to wash the resulting solution• the solution was centrifuged for an hour• Finally, the solid Pt nanoparticles were dried under vacuum at room temperature.
  64. 64. Structural & morphological analyses• TEM: to determine the size of platinum nanoparticles.• Samples: prepared by sonicated (10 min) CCl4 suspension• Suspension drops: deposited onto carbon covered 400-mesh copper grid & the solvent allowed evaporating before analysis.• XPS: to deduce Pt oxidation states• XRD, CV and CA measurements were carried out.• SCE: reference, glassy carbon: counter, catalysts: electrodes
  65. 65. Electrode preparation• C powder (36.78mg) + nafion(0.5mL)+N,N- dimethylformamide(0.15mL)+distilled water 2.5 mL homogeneous solid solution.• the solution: dropped on 7 mm (dia) of glassy carbon electrode.• The electrode: dried at 40, 65C for 20min• The electrode: heated to 100C for 1h adhesion
  66. 66. Further analyses• ICP to determine the Pt amount.• AFM to specify the surface topography.• All measurements:0.01–0.025ohm-cm antimony-doped silicon probes (2 nm R,328– 379 kHz RFs) spring(K)= 20–80 N/m• prepared catalysts: suspended in a deionized water• Solvent evaporated at room temperature
  67. 67. Results & Discussion XRD of blank(a), catalyst I(c), II (d), III(e), and IV (b)
  68. 68. High resolution transition electron micrograph and particle size histogram of catalyst I. Transmission electronmicrograph of catalystIII
  69. 69. a. AFM images of catalysts. b Histogram of height of particles obtained from AFM data. cHistogram of lateral diameter of particles obtained from AFM data
  70. 70. Journal of Power Sources 195 (2010) 1001–10067/26/2012 Synthesis of PdNi catalysts for the oxidation of ethanol in alkaline direct ethanol fuel cells By: A.M.Sheikh LAPEC (Corrosion Research Laboratory) – UFRGS 70
  71. 71. Objective7/26/2012 Is to quantify the quality of PdNi/C catalyst for alkaline DEFC using NaBH4 as reductant, and to use Pd/C for comparison purposes through the XRD, TEM, XPS, ICP-AES tests. 71
  72. 72. Experimental Catalyst Synthesis7/26/2012 • The cehemicals are PdCl2, NiCl2 ·6H2O, KOH, NaBH4, HCl, CH3CH2OH & Vulcan XC-72 carbon (particle size 20–40 nm)+ 5 wt.%(PTFE) emulsion • PdCl2, NiCl2 ·6H2O dissolve in DI water. • C powders: suspended in the resulting • 2 wt.% NaBH4 added 72
  73. 73. 7/26/201273
  74. 74. 7/26/201274
  75. 75. Conclusion7/26/2012 • FCC phase of Pd is present and Ni(OH)2 on the C powder • TEM &EDS images show the well-dispersed metal particles on the C powder & well distribution • CV, CP: Pd2Ni3/C superior activity to EOR • Ni oxidized state distributed over Pd, proved to be enhancing EOR. 75
  76. 76. Journal of Power Sources 218 (2012) 148 - 1567/26/2012 Ni nanowire supported 3D flower-like Pd nanostructures as an efficient electrocatalyst for electrooxidation of ethanol in alkaline media By: A.M.Sheikh LAPEC (Corrosion Research Laboratory) – UFRGS 76
  77. 77. 7/26/201277
  78. 78. Objective7/26/2012 Synthesizing novel hybrid (Ni nano wire array) NiNWA/PdNF(nanoflowers) electrocatalyst using one-dimensional (1D) and conductive metal NiNWA as a support for the PdNF by electrodeposition of NiNWA using polycarbonate template and the reduction of Pd as NF onto the surface of NiNWA through borohydride hydrothermal reduction method. 78
  79. 79. Experimental- Synthesis of NiNWA7/26/2012 • Polycarbonate template was coated by a 400 nm thick layer of Ni using thermal evaporation technique • A Cu wire was connected to the Ni backside of the template by Ag paste • Solution: Nix(So4)y+ NixBry + H2Bo3 + ANKOR • A 2 electrodes cell: anode; Ni pellets in a Ti- basket, cathode; Ni/porous polycarbonate template 79
  80. 80. Synthesis of NiNWA supported PdNF7/26/2012 • NiNWA preparation (0.5 *0.5 cm2) 1 M nitric acid for 1 min washed in DI water • PdNF preparation (NaBH4 hydrothermal reduction with salt (10 mM PdCl2) in water) • NiNWA piece immersed in 5 ml glass tube , 0.5 ml aliquots of Pd metal precursor salt at 80C • NiNWA/PdNF electrocatalyst: removed & washed in Di water 80
  81. 81. 7/26/2012 SEM images (a) NiNWA top view 81
  82. 82. 7/26/2012 SEM images (b) NiNWA supported Pd nanoparticles cross-sectional view. 82
  83. 83. 7/26/2012 BF TEM images of transverse cross-section showing (a) PdNF at the surface of a Ni nanowire, (b) high magnification region of (a), and (c) a full coverage of Pd that varies in thickness from w50 to 100 nm. (d) A diffraction pattern confirming the presence of Ni and Pd, and the lattice parameter of 83
  84. 84. ) Cyclic voltammograms of NiNWA/PdNF in 0.5 M KOH solution, and in 0.5 M KOH þ7/26/2012 1 M EtOH solution in the hydrogen adsorption/desorption region (scan rate: 50 mV s 1 ). Inset shows the magnified view of onset potential region of cyclic voltammograms. (a) Cyclic voltammograms of NiNWA/PdNP and NiNWA/PdNF for the electrooxidation of ethanol in 0.5 M KOH þ 1 M EtOH solution. Conditioning/initial potential: 0.55 V, 20 s; scan rate: 20 mV/s 84
  85. 85. 7/26/2012 (a) Cyclic voltammograms of NiNWA/PdNF for the electrooxidation of ethanol at different scan rates in 0.5 M KOH þ 1 M EtOH solution, (b) Plot of forward anodic peak current density and the corresponding peak potential at different scan rates. 85
  86. 86. Conclusion7/26/2012 • Ni nanowire array supported three dimensional flower- like Pd nano-electrocatalyst and investigated their electrocatalytic performance toward electrooxidation reaction in alkaline media • 1D metallic Ni nanowire array can be used as a noble metal catalyst supports as an alternative to CNTs • Ni nanowire array/Pd nanoflowers electrocatalyst exhibits large electrochemically active surface area , higher stability and poisoning tolerance than Pd nanoparticles • Inherent nature of the abundant grain boundaries and the three-dimensional open nanostructure of the Pd nanoflowers. 86