enzymatic biofuel cells

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Enzymatic Biofuel Cells Presented by: Gurmeet singh 2013PCY7013 Malaviya National Institute of Technology, Jaipur

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Page 1: Enzymatic biofuel cells

Enzymatic Biofuel Cells

Presented by: Gurmeet singh

2013PCY7013

Malaviya National Institute of Technology, Jaipur

Page 2: Enzymatic biofuel cells

INTRODUCTION

Fuel cells are devices that convert chemical energy into electrical energy. Biofuel cells are a subset of fuel cells that employ biocatalysts. The main types of biofuel cells are defined by the type of biocatalyst. Microbial biofuel cells employ living cells to catalyze the oxidation of the fuel, whereas enzymatic biofuel cells use enzymes for this purpose.

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Enzymatic biofuel cells typically possess orders of magnitude higher power densities but can only partially oxidize the fuel and have limited lifetimes (typically 7–10 days).Enzymes have the added advantage of specificity, which can eliminate the need for a membrane separator. A conventional enzymatic fuel cell and the polymer electrolyte membrane (PEM) shown is standard, but if there are selective enzymes on both the cathode and the anode then the PEM is unnecessary.

Continued…

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Enzymetic biofuel cell

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What would it be like if you could recharge your cell phone battery instantly by pouring your soft drink into it?

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Technical challenges surrounding a fuel cell that will run on such simple sugars as those found in our everyday foodstuffs. Most fuel cells in the world today run on hydrogen. However, as the fuel gets more complex, this oxidation process becomes vastly more complicated

Researchers are turning to the natural world in an effort to see how sugars are oxidized by animals to produce power. Using enzymes (nature’s catalysts) seems to be the answer, since they do not suffer from the contamination problems that more traditional metallic catalysts suffer from.

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Action……….

In animals, enzymes are floating freely in the cells of the body, but to work in a fuel cell, they have to be put in a specific place and stay there, a process that scientists call immobilizing the enzymes.

They are also “selective,” a word that scientists use to describe an enzyme’s ability to work with a very specific fuel, and only that fuel, so that the byproduct of one oxidation step could be the fuel for another enzyme.

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A schematic of a generic biofuel cell oxidizing glucose as fuel at the bioanode and reducing oxygen to water at thebiocathode.

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History

Biofuel cells were first introduced in 1911 when Potter cultured yeast and E. Coli cells on platinum electrodes, but it was not until 1962 that the enzymatic biofuel cell was invented employing the enzyme glucose oxidase to oxidize glucose at the anode. Over the last 45 years, many improvements have been made in enzymatic biofuel cells and those can be found in several review articles.

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Recent advances in enzymatic biofuel cells

One of the most significant advances in biofuel cells has been the development of biocathodes and bioanodes that employ direct electron transfer(DET) instead of mediated electron transfer (MET). Enzymes are proteins that typically have short lifetimes (8 h to 2 days) in buffer solution,but Recently, active lifetimes have even been extended beyond 1 year through encapsulation in micellar polymers.

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Principles of biofuel cell design indicting the maximum oxidation potentials for glucose and the corresponding thermodynamic potential for oxygen reduction at neutral pH. Redox potentials of several enzymes and their corresponding co-factors are shown along with the potential “zone” containing the redox potentials of the usual mediators. Polarization curves depict typical current performances for direct and mediated electron transfer in biofuel cell electrodes.

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Fluorescence

The entrapment of enzymes within polymer networks has found numerous applications in the design of bioelectrochemical devices, primarily owing to the simplicity and mild conditions of the procedure and its ability to preserve the catalytic activity of biomolecules.In the context of biosensor and biofuel cell development, electrochemistry has generally been the method of choice when characterizing the performance of polymer- immobilized enzymes. Other methods, such as scanning electron microscopy , infrared spectroscopy, X-ray diffraction , atomic force microscopy.

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Fluorescently tagged enzymes in polymer films. Alcohol dehydogenase in an Eastman AQ membrane as shown (a) in a single plane and (b) in three-dimensions.

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(c) in a single plane and (d) in three dimensions Alcohol dehydogenase in a Nafion membrane shown

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Applications for Biofuel Cells and Their Desirable Features

Implantable - glucose/02/using human derived enzymes; biocompatible. Developing countries - carbohydrates or agricultural and municipal wastes/using microorganisms; robust, low-cost components. Portable - methanol or ethanol/using thermophilic enzymes; high activity (to achieve high power density). Space - human waste/microbial; simplicity in regeneration of catalysts,dual use in environmental management and power generation. Waste Control - waste/microbial; able to handle a large range of feeds.

Applications Fuel/type of catalyst ; Desirable Features

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Conclusions

Enzyme-based biofuel cells have many advantages over traditional fuel cells and primary batteries, they remain limited by short lifetimes, catalytic inefficiencies,low fuel utilization, and low power densities. Recently, working solutions to short lifetimes and catalytic inefficiencies have been introduced, but similar advances in improved fuel utilization and power density are needed. Improvements in these areas will require electrochemical characterization in standardized test geometries, and the use of additional spectroscopic procedures that can be coupled to classic electrochemical measurements.

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REFRENCES……

• WWW.SCIENCEDIRECT.COM

• WWW.WIKIPEDIA.COM

• WWW.GOOGLE.COM

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THANK YOU……