Electrochemistry : Fuel Cells
BY: Maria Shena
Electrochemistry
Electrochemistry is the study of chemical processes that cause electrons to move. This movement of electrons is called electricity, which can be generated by movements of electrons from one element to another in a reaction known as an oxidation-reduction
Electrochemistry is important in the transmission of nerve impulses in biological systems. Redox chemistry, the transfer of electrons, is behind all electrochemical processes. An electrochemical cell is any device that converts chemical energy into electrical energy or electrical energy into chemical energy.
Fuel Cells
A fuel cell uses the chemical energy of hydrogen or another fuel to cleanly and efficiently produce electricity. If hydrogen is the fuel, electricity, water, and heat are the only products. Fuel cells are unique in terms of the variety of their potential applications; they can provide power for systems as large as a utility power station and as small as a laptop computer.
Fuel Cell Types
Fuel cells are classified primarily by the kind of electrolyte they employ. This classification determines the kind of electro-chemical reactions that take place in the cell, the kind of catalysts required, the temperature range in which the cell operates, the fuel required, and other factors. These characteristics, in turn, affect the applications for which these cells are most suitable. There are several types of fuel cells currently under development, each with its own advantages, limitations, and potential applications.
Fuel Cell Types
POLYMER ELECTROLYTE MEMBRANE FUEL CELLS
DIRECT METHANOL FUEL CELLS
ALKALINE FUEL CELLS
PHOSPHORIC ACID FUEL CELLS
MOLTEN CARBONATE FUEL CELLS
SOLID OXIDE FUEL CELLS
REVERSIBLE FUEL CELLS
Why Study Fuel Cells
Fuel cells can be used in a wide range of applications, including transportation, material handling, stationary, portable, and emergency backup power applications. Fuel cells have several benefits over conventional combustion-based technologies currently used in many power plants and passenger vehicles. Fuel cells can operate at higher efficiencies than combustion engines, and can convert the chemical energy in the fuel to electrical energy with efficiencies of up to 60%. Fuel cells have lower emissions than combustion engines. Hydrogen fuel cells emit only water, so there are no carbon dioxide emissions and no air pollutants that create smog and cause health problems at the point of operation. Also, fuel cells are quiet during operation as they have fewer moving parts.
How Fuel Cells Work
Cells are often seen as an alternative to conventional batteries both use electricity but there are a few key differences that you need to be aware of.
First let's take a look at conventional batteries. A battery consist of one or more electrochemical cells which store energy in the chemicals they contain when and external load such as a motor or bulb is connected to a battery. These chemicals react and release electrons which creates an electrical current.
How Fuel Cells Work
The reactants in the conventional battery can be used up, in which case the chemical reaction will stop; but some batteries are rechargeable. If an electric current is supplied from outside to reverse the reaction that normally takes place.
Eventually though, the chemicals in rechargeable batteries would degrade and hold less and less energy and so will need to be disposed of. Often the chemicals used in batteries are toxic and they can be harmful to the environment.
How Fuel Cells Work
Fuel cells don't need to be recharged. They can be used constantly provided that the fuel keeps getting put in. The fuel is normally used in fuel cells, hydrogen, can be a little tricky to store, beacuse it is a very light gas so it needs to be pressurized to make it possible to store a lot of hydrogen in a small space.
However, what makes hydrogen fuel cells so exciting is that their only product is water and when the hydrogen is made renewably, there are no emissions whatsoever making them great for the environment.
How Fuel Cells Work
Fuel cells generate electricity from the reaction between a fuel which is normally hydrogen and oxygen. We know how water can be separated into hydrogen and oxygen. When it turns out that hydrogenand oxygen actually quite like being together, so they'll get back together whenever they have the opportunity. More scientifically speaking, hydrogen gas and oxygen gas will react readily to form water, provided they are given some help to do so. This help can be provided by an external source of energy such as a spark and once they have started to react they can do so very quickly and sometimes with explosive force.
How Fuel Cells Work
In a fuel cell however, the hydrogen and oxygen molecules are kept separate from each other; so they cannot react explosively. They are separated by a special polymer membrane called an electrolyte which does not allow oxygen or hydrogen molecules to pass through it. It does allow positively hydrogen ions known as protons to pass through though. These photons are produced by passing the hydrogen molecules over a platinum metal catalyst which splits them into the protons and electrons. This splitting process is called oxidation. The electrons flow through the anode electrode into an electric circuit to power, for example the motor of a car and eventuallyend up on the oxygen side of the fuel cell. The protons pass through the membrane to the oxygen side where they are able to react with the oxygen molecules and the electrons to produce water in a safe and controlled of manner. Again with the help of another platinum catalyst. This is at the cathode electrode. This is the overall reaction that takes place then in a hydrogen fuel cell.
How Fuel Cells Work
How Fuel Cells Work
So the word equation would be :
Hydrogen + Oxygen Water
Chemically we could express this as:
H2 + O2 H2O
We need to balance this equation by putting a 2 in front of the H2 and a 2 in front of the H2O
2 H2 + O2 2 H2O
How Fuel Cells Work
So a fuel cell will use this process to produce an electrical energy, heat energy and water. It is a very efficient way of converting the potential energy available, especially when compared to normal combustion engine car.
Fuel cells and cars
One potential use for hydrogen fuel cells is in cars. The major advantage of this compared to normal cars is having no polluting emissions.
Although this can be an advantage. In an accident, the hydrogen would just escape into the air unlike a conventional fuel, Which can cause large vehicle fires
The hydrogen gas is however more difficult to store and transport compared to liquid petrol.
Fuel cells and cars
Currently there are not a lot of hydrogen refueling stations across the country and a developing process for making a zero carbon renewable hydrogen is in its infancy.
This means the developing, the infrastructure and the process for producing hydrogen is currently expensive.
This is a disadvantage compared to battery electric cars which can be charged at home and normal cars which have fuel stations everywhere.
Fuel cells and cars
Hydrogen cars can however be refueled more quickly than battery electric cars. In around five minutes compared to several hours to recharge battery car using standered charges .
Batteries holde very little energy compared to a hydrogen tank and a fuel cell system. If a car is to travel 300 miles, it needs 5 Kg of hydrogen, 30 Kg of petrol or 700 Kg of batteries. For larger vehicles and long ranges it becomes impractical for the vehicle to carry the batteries it needs.
Fuel cells and cars
Perpetual cars and battery electric vehicles, the fuel is dependent on a country having access to or buying oil reserves or rare elements needed in batteries.
PETROL CARS
BATTERY CARS
Fuel cells and cars
Luckily for fuel cells though hydrogen is widely available to all.
HYDROGEN CARS
Other Uses of Fuel cells
They have also been developed for uses in homes to produce heat and power in buses and in trains, and in the future could potentially have more technical applications to help our fight against climate change.
Fuel cells have other uses too, they have a history of providing electricity in rockets and have the bonus of producing water for the astronauts.
Sources
A Basic Overview of Fuel Cell Technology, americanhistory.si.edu/fuelcells/basics.htm. “Fuel Cell Basics.” Fuel Cell & Hydrogen Energy Association, www.fchea.org/fuelcells. “Https://Www.netl.doe.gov/Sites/Default/Files/Netl-File/FCHandbook7.Pdf." Libretexts. “20.7: Batteries and Fuel Cells.” Chemistry LibreTexts, Libretexts, 20 Mar. 2021, chem.libretexts.org/Bookshelves/General_Chemistry/Map%3A_Chemistry_-_The_Central_Science_(Brown_et_al.)/20%3A_Electrochemistry/20.7%3A_Batteries_and_Fuel_Cells. Libretexts. “Electrochemistry Basics.” Chemistry LibreTexts, Libretexts, 15 Aug. 2020, chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplemental_Modules_(Analytical_Chemistry)/Electrochemistry/Basics_of_Electrochemistry.
Thanks!
Electrochemistry : Fuel Cells EPRESENTATION
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Transcript
Electrochemistry : Fuel Cells
BY: Maria Shena
Electrochemistry
Electrochemistry is the study of chemical processes that cause electrons to move. This movement of electrons is called electricity, which can be generated by movements of electrons from one element to another in a reaction known as an oxidation-reduction
Electrochemistry is important in the transmission of nerve impulses in biological systems. Redox chemistry, the transfer of electrons, is behind all electrochemical processes. An electrochemical cell is any device that converts chemical energy into electrical energy or electrical energy into chemical energy.
Fuel Cells
A fuel cell uses the chemical energy of hydrogen or another fuel to cleanly and efficiently produce electricity. If hydrogen is the fuel, electricity, water, and heat are the only products. Fuel cells are unique in terms of the variety of their potential applications; they can provide power for systems as large as a utility power station and as small as a laptop computer.
Fuel Cell Types
Fuel cells are classified primarily by the kind of electrolyte they employ. This classification determines the kind of electro-chemical reactions that take place in the cell, the kind of catalysts required, the temperature range in which the cell operates, the fuel required, and other factors. These characteristics, in turn, affect the applications for which these cells are most suitable. There are several types of fuel cells currently under development, each with its own advantages, limitations, and potential applications.
Fuel Cell Types
POLYMER ELECTROLYTE MEMBRANE FUEL CELLS DIRECT METHANOL FUEL CELLS ALKALINE FUEL CELLS PHOSPHORIC ACID FUEL CELLS MOLTEN CARBONATE FUEL CELLS SOLID OXIDE FUEL CELLS REVERSIBLE FUEL CELLS
Why Study Fuel Cells
Fuel cells can be used in a wide range of applications, including transportation, material handling, stationary, portable, and emergency backup power applications. Fuel cells have several benefits over conventional combustion-based technologies currently used in many power plants and passenger vehicles. Fuel cells can operate at higher efficiencies than combustion engines, and can convert the chemical energy in the fuel to electrical energy with efficiencies of up to 60%. Fuel cells have lower emissions than combustion engines. Hydrogen fuel cells emit only water, so there are no carbon dioxide emissions and no air pollutants that create smog and cause health problems at the point of operation. Also, fuel cells are quiet during operation as they have fewer moving parts.
How Fuel Cells Work
Cells are often seen as an alternative to conventional batteries both use electricity but there are a few key differences that you need to be aware of.
First let's take a look at conventional batteries. A battery consist of one or more electrochemical cells which store energy in the chemicals they contain when and external load such as a motor or bulb is connected to a battery. These chemicals react and release electrons which creates an electrical current.
How Fuel Cells Work
The reactants in the conventional battery can be used up, in which case the chemical reaction will stop; but some batteries are rechargeable. If an electric current is supplied from outside to reverse the reaction that normally takes place.
Eventually though, the chemicals in rechargeable batteries would degrade and hold less and less energy and so will need to be disposed of. Often the chemicals used in batteries are toxic and they can be harmful to the environment.
How Fuel Cells Work
Fuel cells don't need to be recharged. They can be used constantly provided that the fuel keeps getting put in. The fuel is normally used in fuel cells, hydrogen, can be a little tricky to store, beacuse it is a very light gas so it needs to be pressurized to make it possible to store a lot of hydrogen in a small space.
However, what makes hydrogen fuel cells so exciting is that their only product is water and when the hydrogen is made renewably, there are no emissions whatsoever making them great for the environment.
How Fuel Cells Work
Fuel cells generate electricity from the reaction between a fuel which is normally hydrogen and oxygen. We know how water can be separated into hydrogen and oxygen. When it turns out that hydrogenand oxygen actually quite like being together, so they'll get back together whenever they have the opportunity. More scientifically speaking, hydrogen gas and oxygen gas will react readily to form water, provided they are given some help to do so. This help can be provided by an external source of energy such as a spark and once they have started to react they can do so very quickly and sometimes with explosive force.
How Fuel Cells Work
In a fuel cell however, the hydrogen and oxygen molecules are kept separate from each other; so they cannot react explosively. They are separated by a special polymer membrane called an electrolyte which does not allow oxygen or hydrogen molecules to pass through it. It does allow positively hydrogen ions known as protons to pass through though. These photons are produced by passing the hydrogen molecules over a platinum metal catalyst which splits them into the protons and electrons. This splitting process is called oxidation. The electrons flow through the anode electrode into an electric circuit to power, for example the motor of a car and eventuallyend up on the oxygen side of the fuel cell. The protons pass through the membrane to the oxygen side where they are able to react with the oxygen molecules and the electrons to produce water in a safe and controlled of manner. Again with the help of another platinum catalyst. This is at the cathode electrode. This is the overall reaction that takes place then in a hydrogen fuel cell.
How Fuel Cells Work
How Fuel Cells Work
So the word equation would be :
Hydrogen + Oxygen Water
Chemically we could express this as:
H2 + O2 H2O
We need to balance this equation by putting a 2 in front of the H2 and a 2 in front of the H2O
2 H2 + O2 2 H2O
How Fuel Cells Work
So a fuel cell will use this process to produce an electrical energy, heat energy and water. It is a very efficient way of converting the potential energy available, especially when compared to normal combustion engine car.
Fuel cells and cars
One potential use for hydrogen fuel cells is in cars. The major advantage of this compared to normal cars is having no polluting emissions.
Although this can be an advantage. In an accident, the hydrogen would just escape into the air unlike a conventional fuel, Which can cause large vehicle fires
The hydrogen gas is however more difficult to store and transport compared to liquid petrol.
Fuel cells and cars
Currently there are not a lot of hydrogen refueling stations across the country and a developing process for making a zero carbon renewable hydrogen is in its infancy.
This means the developing, the infrastructure and the process for producing hydrogen is currently expensive.
This is a disadvantage compared to battery electric cars which can be charged at home and normal cars which have fuel stations everywhere.
Fuel cells and cars
Hydrogen cars can however be refueled more quickly than battery electric cars. In around five minutes compared to several hours to recharge battery car using standered charges .
Batteries holde very little energy compared to a hydrogen tank and a fuel cell system. If a car is to travel 300 miles, it needs 5 Kg of hydrogen, 30 Kg of petrol or 700 Kg of batteries. For larger vehicles and long ranges it becomes impractical for the vehicle to carry the batteries it needs.
Fuel cells and cars
Perpetual cars and battery electric vehicles, the fuel is dependent on a country having access to or buying oil reserves or rare elements needed in batteries.
PETROL CARS
BATTERY CARS
Fuel cells and cars
Luckily for fuel cells though hydrogen is widely available to all.
HYDROGEN CARS
Other Uses of Fuel cells
They have also been developed for uses in homes to produce heat and power in buses and in trains, and in the future could potentially have more technical applications to help our fight against climate change.
Fuel cells have other uses too, they have a history of providing electricity in rockets and have the bonus of producing water for the astronauts.
Sources
A Basic Overview of Fuel Cell Technology, americanhistory.si.edu/fuelcells/basics.htm. “Fuel Cell Basics.” Fuel Cell & Hydrogen Energy Association, www.fchea.org/fuelcells. “Https://Www.netl.doe.gov/Sites/Default/Files/Netl-File/FCHandbook7.Pdf." Libretexts. “20.7: Batteries and Fuel Cells.” Chemistry LibreTexts, Libretexts, 20 Mar. 2021, chem.libretexts.org/Bookshelves/General_Chemistry/Map%3A_Chemistry_-_The_Central_Science_(Brown_et_al.)/20%3A_Electrochemistry/20.7%3A_Batteries_and_Fuel_Cells. Libretexts. “Electrochemistry Basics.” Chemistry LibreTexts, Libretexts, 15 Aug. 2020, chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplemental_Modules_(Analytical_Chemistry)/Electrochemistry/Basics_of_Electrochemistry.
Thanks!