Chemistry Issue Investigation(Draft)

7/27/2019 Chemistry Issue Investigation(Draft)

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CHEMISTRY ISSUE INVESTIGATION

DRAFT

Is hydrogen fuel cell a viable alternative to petrol powered car?

Introduction

Due to the scarcity of fuels, its price is continuously rising and growing concern for the

global environment. More focus is being given to the hydrogen fuel cell as a

replacement for burning fossil fuels. Hydrogen fuel cell is an electrochemical conversion

device that converts the chemical energy from a fuel into electricity through a chemical

reaction with oxygen. Hydrogen is the most common fuel, but hydrocarbons such as

natural gas and alcohols like methanol are sometimes used. In a fuel cell, hydrogen and

oxygen are constantly flow into the cell, which is then produced electricity in order to

power the car. Because hydrogen and oxygen gases are electrochemically converted intowater, fuel cells have more benefits over petrol cars. Hydrogen fuel cell is very efficient,

does not involve any moving parts and does not produce any polluting gases.

Chemical Background of Hydrogen Fuel Cell

Figure 1: Schematic Diagram of a Proton Exchange Membrane (PEM) Fuel Cell


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The fuel cell used to power a vehicle is known as Proton Exchange Membrane (PEM) Fuel

Cell. It is also referred as Polymer Electrolyte Membrane Fuel Cell. In a PEM fuel cell, , two half-cell

reactions take place simultaneously, an oxidation reaction (loss of electrons) at the anode and a

reduction reaction (gain of electrons) at the cathode. These two reactions make up the total

oxidation-reduction (redox) reaction of the fuel cell, the formation of water from hydrogen and

oxygen gases.

As in the electrolysers, the anode and cathode are separated by an electrolyte, which allows

ions to be transferred from one side to the other. The electrolyte in a PEM fuel cell is a solid acid

supported within the membrane. The solid acid electrolyte is saturated with water so that the

transport of ions can proceed.

Anode reaction: H2 2H+ + 2e-

Cathode reaction:

O2 + 2e

- + 2H+ H2O (l)

Overall reaction: H2 +

O2 H2O (l)

At the anode, the hydrogen molecules first come into contact with a platinum catalyst on

the electrode surface. The hydrogen molecules break apart, forming a bond with the surface of

platinum. As the hydrogen molecule is now broken the oxidation reaction can proceed. Each

hydrogen atom releases its electron, which travels around the external circuit to the cathode (it is

this flow of electrons that is referred to as electrical current). The remaining hydrogen proton bonds

with a water molecule on the membrane surface, forming a hydronium ion (H3O+). The hydronium

ion travels through the membrane material to the cathode, leaving the platinum catalyst site free for

the next hydrogen molecule.

At the cathode, oxygen molecules come into contact with a platinum catalyst on the

electrode surface. The oxygen molecules break apart forming a weak bonding at the surface of

platinum, enabling the reduction reaction to proceed. Each oxygen atom then leaves the platinum

catalyst site, combining with two electrons (which have travelled through the external circuit) and

two protons (which have travelled through the membrane) to form one molecule of water. The

redox reaction has now been completed. The platinum catalyst on the cathode electrode is again

free for the next oxygen molecule to arrive.

However the source of hydrogen doesnt come from the air. Hydrogen gas is produced froma process known as Natural Gas Reforming. Natural gas contains methane (CH4) that can be used

to produce hydrogen with thermal processes, such as steam-methane reformation and partial

oxidation.


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Steam-Methane Reforming

Most hydrogen produced today is made from steam-methane reforming, a process which

high-temperature steam (700C1,000C) is used to produce hydrogen from a methane source, such

as natural gas. In steam-methane reforming, methane reacts with steam under 325 bar pressure (1

bar = 14.5 psi) in the presence of a catalyst to produce hydrogen, carbon monoxide, and a relativelysmall amount of carbon dioxide. Steam reforming is an endothermic reaction whereby heat must be

supplied to the process for the reaction to proceed.

Chemical equation: CH4 + H2O (+heat) CO + 3H2

Partial Oxidation

In partial oxidation, the methane and other hydrocarbons in natural gas react with a limited

amount of oxygen (typically from air) that is not enough to completely oxidize the hydrocarbons to

carbon dioxide and water. With small amount of oxygen available, the reaction products containmostly hydrogen and carbon monoxide (and nitrogen, if the reaction is carried out with air rather

than pure oxygen), and a relatively small amount of carbon dioxide and other compounds.

Subsequently, in a water-gas shift reaction, the carbon monoxide reacts with water to form carbon

dioxide and more hydrogen.

Chemical equation: CH4 +

O2 CO + 2H2 + heat

Points of View

Advantages of Hydrogen Fuel cell

Hydrogen fuel cell is very efficient compared to petrol car.

They convert hydrogen and oxygen directly into electricity and

water, with no combustion within the process; petrol car undergoes

combustion process where heat is loss along the process, thus

reduces its efficiency.

Hydrogen fuel cell does not produce any polluting gases.

A fuel cell does not undergo combustion process. Therefore it

produces no emission of sulphur dioxide which can lead to acid rainand no emission of nitrogen oxides which produce smog or dust

particulates.

In a petrol car, it involves combustion process where harmful waste

products are produced which causes global warming, formation of

acid rain and greenhouse effect.

Hydrogen fuel cell does not contain any moving parts.

With no moving parts in the fuel cell, it does not require any

maintenance. As a result, electrical power produced is relatively

silently.


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The engine in a petrol car contains moving parts such as pistons and

fans. Therefore, maintenance is required in order to prevent the car

from breakdown.

Disadvantages of Hydrogen Fuel Cell

Hydrogen fuel cell is costly.

Due to the presence of pure hydrogen and oxygen which is first

produced, followed by storing as a carrier and the existence of

precious metal (Platinum) as a catalyst, It raises the cost up to

$300,000 per car which is 5x the price of a petrol car.

Hydrogen gas is very explosive.

When hydrogen gas which is previously mixed with oxygen isexposed to the air, it will create an explosion that may cause fatality.

Safety measures must be taken in order to insulate the fuel.

There are limited fuelling stations of hydrogen fuel.

Hydrogen is not easily available at fuelling stations and the

availability of hydrogen for easy fuelling requires large infrastructure.

Alternative Point Of View

Hydrogen can be obtained using steam reforming. However, this production method

has produces carbon dioxide as a by-product which contributes to negative environmental

impact Therefore, it defeat the purpose of using hydrogen fuel cell.

1 Car with internal combustion engine2 Fuel cell car with hydrogen produced from coal generation

3 Fuel cell car with gasoline reformer4 Fuel cell car with methanol reformer5 Fuel cell car using hydrogen from natural gas (distributed from urban retail outlets)6 Fuel cell car using hydrogen from natural gas (made at large refineries)


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Figure 2. Graph comparing carbon dioxide emissions of cars, using different types of fuel sources.

Conclusion

Hydrogen fuel cells are an attractive alternative to oil dependency. Fuel cells give off no

pollution, and in fact produce pure water as a by-product. In order to cope with the depletion of

non- renewable sources, hydrogen fuel cell should be encouraged to sustain the environment.

References

Bellis, 2000, Hydrogen Fuel Cells,

http://inventors.about.com/od/fstartinventions/a/Fuel_Cells_2.htm

Brown, Bursten, Lemay, Murphy & Woodward, 2012, Chemistry The Central Science, Twelfth

Edition, ed. Adam Jaworski, Pearson Prentice Hall, United States of America, pp. 856-857.

Cook, 2001, An Introduction To Fuel Cell and Hydrogen Technology, no.6, pp.26, accessed 14 July

2013

http://fuelcellstore.com/products/heliocentris/intro.pdf

Dana1981, Teej, Stins, Jenifer, Neytie, 2008, Hydrogen Cars

http://www.greenoptions.com/a/hydrogen-cars

Davies, 2013, A Hydrogen-Powered Car Could Someday Be Sitting In Your Driveway

http://www.businessinsider.com/pro-con-future-of-hydrogen-fuel-cell-electric-vehicles-fcev-2013-4

Fuel cell hydrogen energy association, 2009, Hydrogen Production From Coal

http://www.fchea.org/core/import/PDFs/factsheets/Hydrogen%20Production%20From%20Coal_NE

W.pdf

James Madison University, 2003, Alternative Fuel Data Center

http://www.afdc.energy.gov/fuels/hydrogen_basics.html
http://inventors.about.com/od/fstartinventions/a/Fuel_Cells_2.htmhttp://fuelcellstore.com/products/heliocentris/intro.pdfhttp://www.greenoptions.com/a/hydrogen-carshttp://www.businessinsider.com/pro-con-future-of-hydrogen-fuel-cell-electric-vehicles-fcev-2013-4http://www.fchea.org/core/import/PDFs/factsheets/Hydrogen%20Production%20From%20Coal_NEW.pdfhttp://www.fchea.org/core/import/PDFs/factsheets/Hydrogen%20Production%20From%20Coal_NEW.pdfhttp://www.afdc.energy.gov/fuels/hydrogen_basics.htmlhttp://www.afdc.energy.gov/fuels/hydrogen_basics.htmlhttp://www.fchea.org/core/import/PDFs/factsheets/Hydrogen%20Production%20From%20Coal_NEW.pdfhttp://www.fchea.org/core/import/PDFs/factsheets/Hydrogen%20Production%20From%20Coal_NEW.pdfhttp://www.businessinsider.com/pro-con-future-of-hydrogen-fuel-cell-electric-vehicles-fcev-2013-4http://www.greenoptions.com/a/hydrogen-carshttp://fuelcellstore.com/products/heliocentris/intro.pdfhttp://inventors.about.com/od/fstartinventions/a/Fuel_Cells_2.htm


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Nice, Strickland, 2007, How Fuel Cells Work

http://auto.howstuffworks.com/fuel-efficiency/alternative-fuels/fuel-cell4.htm

Santany, 2007, How Does a Hydrogen Fuel Cell Work

http://www.ehow.com/how-does_4568949_hydrogen-fuel-cell-work.html

West, 2005, Is Hydrogen the Fuel of the Future?

http://environment.about.com/od/fossilfuels/a/fcv.htm
http://auto.howstuffworks.com/fuel-efficiency/alternative-fuels/fuel-cell4.htmhttp://auto.howstuffworks.com/fuel-efficiency/alternative-fuels/fuel-cell4.htmhttp://www.ehow.com/how-does_4568949_hydrogen-fuel-cell-work.htmlhttp://www.ehow.com/how-does_4568949_hydrogen-fuel-cell-work.htmlhttp://environment.about.com/od/fossilfuels/a/fcv.htmhttp://environment.about.com/od/fossilfuels/a/fcv.htmhttp://environment.about.com/od/fossilfuels/a/fcv.htmhttp://www.ehow.com/how-does_4568949_hydrogen-fuel-cell-work.htmlhttp://auto.howstuffworks.com/fuel-efficiency/alternative-fuels/fuel-cell4.htm

Chemistry Issue Investigation(Draft)

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