ENERGY MATERIALS FOR FUEL CELL

 

 

ElectroCatalytic EnergyMaterials      Pt based Energy Materials          Non-Pt based Energy Materials  

NanoStructur Energy Materials                Materials Synthesis                 Materials Characterization

Non-Pt based Energy Materials

Non Pt based inexpensive, high electro catalytic activity materials need to be developed for fuel cell electrodes to produce renewable green energy from biomass at cheap rate.  Several oxides and metal alloys have been found to show good electro catalytic properties. Materials such as CoTi  , PbO2 , TiO2  and β-MnO2  show very  encouraging results for application in fuel cell electrodes.  Paul et al  produced MnO2 and MnO2-nano carbon electrodes by electro synthesis to produce clean energy through a fuel cell, using glucose as fuel. Nano composite metal oxides, ZnO-Al2O3 produced by paul et al performed as very good electro catalytic energy material as glucose fuel cell electrode.   There are a few works on Ni based alloy electrodes development for fuel cell. A small addition of Al to Ni produced an improved electrode property as cathode in molten carbonate fuel cells (MCFC) . A wide compositional range of Ni–Pd alloy catalysts were prepared by Suresh Kumar for application as anode materials for methanol oxidative fuel cells in alkaline conditions .

 

Materials Characterization

The operating parameters of nanomaterials synthesis by electrodeposition

should be first determined by conducting the following laboratory experiments.

 

Cyclic voltammetry


Chronoamperometric


 Potentiodynamic polarization


X ray diffraction


 Electron microscopy (SEM/TEM)


Cyclic voltammetry, the potential is scanned through a potential, starting from a potential well below the potential for cathodic reduction of the half cell reaction to that over the potential of anodic oxidation of other half cell reaction. In cyclic voltammetry curve, two peaks canbe observed: cathodic reduction and anodic oxidation of the ions.

 

Chronoamperometric is conducted to study I = f(t) at differentfixed potentials preselected around deposition potential. Such measurement gives us additional qualitative and quantitative information about electrolyte composition, speed of electrode processes and chemical reaction taking place at the electrodes and in electrolyte. Chronoamperometric curves should be registered at potential exceeding overpotential value.


Potentiodynamic polarization, the potential is scanned from cathodic to anodic side, and corresponding current are recorded. From the graph and experimental data, all electrokinetic parameters such as Tafel slope, exchange current density, limiting current density, overvoltage and so on are determined.1–5 Depending on applied deposition potential/current, an electrodeposition can be charge transfer controlled or mass transfer controlled. The polarization curve thus guides the selection of deposition potential. The exchange current determination helps to select the physical properties of the substrate on which nanodeposit is produced. A substrate with low exchange current density produces finer deposit.

 

X ray diffraction graph exhibits the constituents of the deposit materials and their characteristics. The grain size of the deposit can be estimated from the peak intensity data , using, Scherrer formula.

 

SEM/TEM

The morphology of the nano electro deposit structure is revealed under scanning electron microscope which displays a 3D image  and nano grain size can be determined from the image. To determine the grain size more accurately Transmission electron microscope which exhibits a 2D image is adopted.

 

   High Current Delivered Non Pt based Energy Materials

 Pt based Energetic Materials

Nano pores  anodized Al   are filled up  by Pt + Ru  & Pt+Ru+C by electrodeposition

 

Materials Synthesis : Electrodeposition

The electrochemical deposition method is superior, because of its low  reaction temperature, the controllability of the thickness and shape, high deposition rate, low-cost equipment, nontoxicity and eco-friendly feature, and more importantly, thethin films deposited are crystalline structure. Electrodeposition can be carried out by deposition of pure metal and alloys1,2,5at cathode or oxides and hydroxides3,4,8–10 at anode/cathode.By using electroplating method, the graded coatings can
easily be manufactured by changing the process variables, likecurrent density, applied potential, chemistry of the electrolyte, temperature, pH, stirring and particle loading in the bath.
Among these parameters, the imposed current is one of the most important one, having a great influence on particle content in the composite coating and consequently on coating properties. Different types of currents like direct current (DC), pulsed current (PC) and pulsed reversed current have been employed. PC has been proved to be a useful tool for designing metallic coating properties.

NanoStructured Energy Materials

They possess much enhanced electronic, electrical, mechanical, optical, magnetic and electrocatalytic properties .

SEM Image of Nano Structured Energy Materials

Nano Electrodeposition controlling Parameters

Materials

Substrate

Electrolyte composition m/l

Current Density mA/cm2

Potential

volt

pH

Tem

oC

Time

min

Fuel

Ni-Co

Al

NiSO4,7H2O  0.53-0.63

NiCl2,6H2O  0.126

CoSO4,7H2O 0.038

H3BO3

NH4)2SO4

30-80

6-7

4.8-5

65-70

10

1(M) methanol and 0.5(M) H2SO4

MnO2

304

0.6 M MnSO4, +

0_34 M H2SO4

50-150

4-6

11-14

150

45

1 (M)

methanol and 0.5 (M) H2SO4,

MnO2-C

304

MnSO4: 0·25–0·4

H2SO4: 0·55–0·6

C- 0.2

214-270

4-6

11-14

150

5

1 M potassium hydroxide (KOH) and 0·5 M glucose

ZnO-Al2O3

Al

0.5M ZnCl2 +

0.2 M KCl (conductivity) bubbling with air

160-100 mA/cm2

-1.4volt (vs SCE

4 - 8

220- 700

3-6

in glucose solution in phosphate buffer (K2HPO4/KH2PO4) at pH 7.4

Ni coating

Cu

NiCl2.xH2O= 0.5 M                           NiSO4.xH2O= 0.25 M                           Boric Acid=  30g/Lit

0-1

0-50

Pulse coating

-0.31 to

 -0.645 vs SCE

4.1

40

30 cycles

ton 5sec

toff 20 sec

Ethanol 1m

KOH 1M

Ni+ CeO2

Cu

  Above+

 Ce(SO4)2 4H2O  0.1M                  

  KCl 0.1M

0-5

0-300

Pulse coating

 

0.2 to 0.9

4.6

25

30 cycles

ton 5sec

toff 20 sec

Ethanol 1m

KOH 1M

Pt+Ru+C

2 stage anodized Al in H2SO4+ Oxalic

H2PtCl6  6H2O RuCl3

140

0.05–0.2 V

 

70

 

Bio alocohol from Rice husk

 

        

 

 Nano Properties

Large surface area/volume ratio

 

 High atoms density on surface:

 

Enhanced Charge density

 

Inter network morphology

 

Effect on Electrode Reaction

 

Increased effective Electrode surface area for charge/discharge reaction

 

 

High Electrocatalytic Activity

 

 

Higher Current delivered from cell with minimum overvoltage

 

 

 

 

 

Pt based Energy Materials

 Platinum is a good electrode with high exchange current density for anodic and cathodic reactions of the many low temperature fuel cells. However, the performance of a pure Pt catalyst suffers considerable deterioration due to the formation of strongly adsorbed poison species. In particular, Pt is an excellent catalyst for the dehydrogenation but, on the other hand, it is extremely susceptible to poisoning by CO and halides .
These remain strongly adsorbed on the Pt surface and block the active sites from further catalysis, resulting in a dramatic decrease in efficiency and overall performance. Efforts to minimize this poisoning have been centered around with the addition of cocatalysts such as Ru, Sn, Au, W, Mo, Os, Re, Rh, Pd, Pb, Bi, and Ir to Pt to promote CO oxidation . Platinum-based nanomaterials with high surface areas have been receiving increased attention due to their unique properties and a number of impressive applications in catalysis and fuel cells.

 

Electrocatalytic Materials

Since the fuel in the fuel cell is electrochemically oxidized at anode and the output current is delivered at the cathode, the materials and surface properties of the anode and cathode are the most important parts of all activities of fuel cell development. A good anode material should have the electro catalytic property for fast electrochemical oxidation of the fuel along with good electrical conductivity, low polarization resistance, strong biocompatibility, chemical stability and anti-corrosion property.  A cathode material on other hand should have capacity to capture and transfer electron rapidly with high redox potential besides low polarization resistance