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Fundamentals of Electrocatalyst for fuel cell

This article deals with electrocatalyst for fuel cell.  Aims and objectives of research related to electrocatalyst for fuel cell.  Possible out come and future prospective.

Development of Pt-based Composite as Anode Material for Electrocatalytic Oxidation of Methanol

  1. Background and Significance of nanoparticles based electrocatalyst for fuel cell

The burning issues such as energy crisis and environmental pollution have significantly diverted research interest toward sustainable development of alternative energy sources. In this scenario, the development of fuel cells is a promising technology to overcome future energy challenges. Direct methanol fuel cell (DMFC) has received the utmost attention in transportation applications and portable devices due to its efficient energy conversion, low emission of pollutants and facile handling of the liquid fuels. However, the performance of DMFCs in practical application is strongly limited by catalytic instability and sluggish-anode kinetics. So, development of efficient DMFCs for practical applications is a fascinating research domain.

Platinum nanoparticles (PT-NPs) are usually used as anode material in DMFC owing to their outstanding electrocatalytic performance for methanol oxidation (MO). Several approaches such as synthesis of shape controlled Pt-NPs, fabrication of Pt-based binary and ternary electrocatalysts and development of a suitable conductive support for anchoring nanoparticles are adopted to enhance the electrocatalytic potential. Fabrication of suitable support for Pt-NPs is a useful approach for fuel cell development. A good support material leads to high dispersion, improved catalytic efficiency, greater stability and good poisoning tolerance of the catalyst. Previously, carbon black, Reduced graphene oxide (RGO), carbon nanotubes (CNTs) and conducting polymers (CPs) have been explored as effective supports for Pt-NPs. However, CPs as host-material has received the utmost attention owing to their high conductivity, good stability, poisoning tolerance and good interaction with catalyst. Besides this, CPs are proton conducting so these materials have the potential to replace expensive nafion used in fuel cells. Hence, CP modified electrode represents a smart choice as host material for Pt-NPs.

Recent research investigations have unveiled that incorporation of CNTs in the polymer skeleton leads to improvement in electrocatalytic potential and stability of Pt-NPs due to synergistic effects. On the other hand, the catalyst-poisoning tolerance can be enhanced by incorporation of RGO in CP-film. Actually, oxygen containing functional groups of RGO provides anchoring sites for Pt-NPs which results in high stability and dispersion of catalyst. Literature survey reveals that polyaniline, polythiophene and polypyrrole are widely investigated as support materials. Polyindoles and polycarbazoles are also applied for the same purpose in DMFCs. But the issues of low efficiency and catalyst poisoning still persist. The first challenge is addressed by applying CPs and their composites (with CNTs) as anchoring platform for Pt-NPs. While the second issue can be resolved by the incorporation of RGO in the electrodeposited CP-film.

  1. Aims and objectives

Novel ideas about the preparation of new materials bestowed with useful applications are always a challenge for the materials scientists. The dramatic advances in sciences and technology compel us to use high throughput quest for development of novel materials that might give positive-feedback in various walks of life. Doubtlessly, CPs have been extensively studied as support for Pt but still the composites have not been developed enough to satisfy the needs for practical applications. To bridge this gap, we intend to develop three series of novel promising electrocatalyst for MO-reaction with the following specific objectives;

  • Development of platinum/conducting polymer (Pt/CPs) composite electrocatalysts for efficient oxidation of methanol.
  • To further enhance the electrocatalytic potential of Pt/CPs catalyst, by the introduction of CNTs in CP-film to get Pt/CNTs composite anode material.
  • To enhance the stability, dispersion and poisoning tolerance of the composites, we will incorporate graphene in the CP-film
  1. Plan of action

Conducting polymers such as 2-ethoxyaniline, 3,4-(Methylenedioxy)aniline, 2-Isopropoxyaniline, 5-(Benzyloxy)indole and 5,6-Dimethoxyindole will be chosen for building CP-film at GCE as anchoring skeleton for Pt-NPs. In the current work, three series of novel composite anode materials each having five electrocatalyst will be developed via electrodeposition method.

3.1.      Development of Pt/CPs composite electrocatalyst for fuel cell

3.1.1.   Electrodeposition

  • The CPswill be deposited over the surface of clean ultrasonically rinsed glassy carbon electrode (GCE) via electrodeposition (ED) method. In this way, a highly conductive, stable and strong interactive platform is expected to be developed for anchoring Pt-NPs.
  • The resultant polymer film at GC-surface will then be exposed to electrodeposition of Pt-NPs at constant deposition potential. This will result in the building of a highly porous and rough surface having remarkable catalytic properties of Pt-NPs over the CP-skeleton.
  • For comparison, Pt-NPs will be deposited at a bare GCE by following the above procedure.
    • Development of Pt/CPs-CNTs composite electrocatalyst

For further enhancement of the conducting properties of electrocatalyst, CNTs will be incorporated in the polymer matrix as follows;

  • Electrodeposition
  • The composite catalyst will be prepared by facile single step electro-deposition approach. CNTs (dispersed in Trition X-100) will be added to 0.25 M solution of monomers having 1M HCL followed by scanning the GCE-potential within certain limits for electrodeposition via cyclic voltammetry.
  • In the next step, the Pt-nanostructures will be fabricated over CP/CNTs composite by electro-deposition from 0.30 M H3PO4 and 3 MMH2PtCl6
    • Development of Pt/CPs-Graphene composite electrocatalyst for fuel cell

To enhance stability, dispersion and poisoning tolerance of electrocatalyst, we will incorporate graphene in the CP-film.

  • Electrodeposition
  • Graphene/Conducting-polymer composite film will be synthesized via a facile single step electrodeposition method by using monomers and graphite oxide (GO). Initially, both the reagents will be mixed in H2SO4 followed by adding the suspension to clean GCE and then the potential of electrode will be scanned between certain potential limits. Consequently, the monomers will be polymerized and GO reduced to graphene leading to CPs/RGO composite.
  • Afterwards, the Pt- NPs will be electrodeposited from a solution containing 3 mMH2PtCl6 and 0.30 M H3PO4 over the graphene/CP modified electrode.
    • Characterization

The synthesized three series of composite materials will be characterized by using the following techniques.

  • Scanning Electron Microscopy (SEM)
  • Morphology and surface features of the composite materials including confirmation of Pt-NPs electro-deposition into the CP-film at GC-surface will be evidenced by SEM.
    • X-Ray Diffraction Analysis(XRD)
  • The successful incorporation of Pt-NPs into the matrix will be ensured by employing this technique.
    • Cyclic Voltammetry (CV)
  • CV will be applied for electrodeposition of CP-film at the GCE by recording consecutive CVs in the same solution.
  • The electrochemically deposited polymer-film will be characterized by using CV in order to through light on its general redox behaviour.
  • The electrocatalytic potential of the composites will be assessed from methanol electro-oxidation via CV.
    • Electrochemical Impedance Spectroscopy (EIS)
  • Besides CV, EIS will also be applied to probe the catalytic behaviour of the composites in terms of charge transfer resistance for MO-reaction. Hence, confirmation of catalytic potential from two different techniques will definitely add to authenticity of the results.
    • Chronoamperpmetry
  • The poisoning-tolerance of all the composite catalystswill be tested by chronoamperpmetry.
  1. Expected outcome

The horizon of fuel cell has silvery lining to solve future energy challenges. In general, the novel electrocatalysts are expected to develop the catalytic performance to the level of practical applications leading to attract significant attention from academia and industries. Specifically, the following milestones will be achieved during this journey.

  • The synthesized first series nanocomposites are expected to exhibit superior conductivities, even higher than the polyaniline.
  • Incorporation of CNTs in the support material will trigger its conducting and dispersionproperties leading to superior performance for MO-reaction.
  • Finally, incorporation of graphene in the CP-skeleton is expected to improve stability, dispersion and poisoning tolerance of Pt-NPs.
  1. Summary

Low efficiency and poisoning of electrocatalyst are the two critical challenges regarding DMFC development. Here, the first challenge is addressed by using CPs and then CP/CNTs composite as host material for Pt-NPs while the second issue is tackled by the synthesis of novel CP/RGO composites. Initially, a highly porous, conductive and strong catalyst interactive CP-film is built over GCE via electrodeposition. After that, Pt-NPs are electrodeposited over the polymer film to get novel Pt/CPs composites. The electrocatalyst are characterized by various techniques including CV for evaluation of catalytic performance for MO-reaction. The efficiency of the Pt/CPs-composites catalyst is further enhanced by incorporation of CNTs in the CP-film at GC-surface. This is achieved through single step facile electrodeposition of CNTs and monomers over GCE.Finally, we will incorporate graphene in the CP-skeleton via electrodeposition to synthesize Pt/CPs-RGO composite.The developed first series electrocatalyst are expected to exhibit high electrocatalytic activity than polyaniline. The incorporation of CNTs will further enhance the electrocatalytic properties via synergistic effects. Furthermore, incorporation of RGO is expected to dramatically improve stability and dispersion of Pt-NPs due to oxygen functional groups of RGO which provides anchoring sites for nanoparticles.

  1. Future Perspectives

Being a multidimensional approach, the novel smart materials can be applied to catalyze formic acid oxidation for FAFCs development and small organic molecules oxidation for miscellaneous purposes. Moreover, the synthesized composites can be properly developed for application in micro-batteries and energy storage devices like supper capacitors etc. The poisoning due to CO production can be avoided by using Ru which will serve as catalyst promoter for oxidizing CO to CO2

Role Pt/Ru electrocatalyst for fuel cell

Figure showing role Pt/Ru electrocatalyst for the oxidation of methanol

About Syed Noman ud din

Syed Noman ud din is an Electrical Engineer and working in Industry from last 3 years. He writes technical articles for electrical and electronic engineers. He has also published several research publications in renowned international journals.

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