What does a fuel cell convert into electricity?
Chemical energy of a fuel.
What ions react with oxygen in a fuel cell?
Positively charged hydrogen ions.
What do fuel cells require continuously to operate?
A continuous source of fuel and oxygen or air.
How do fuel cells differ from batteries in fuel supply?
Fuel cells need continuous fuel and oxygen; batteries use internal chemicals.
What components does a fuel cell use to separate ion and electron transport?
An anode, an electrolyte, and a cathode.
What is the function of the electrolyte in a fuel cell?
It allows ions to pass but prevents electrons from passing.
What voltage does a typical fuel cell produce at full rated load?
0.6 V to 0.7 V.
How does a fuel cell's voltage change as current increases?
The voltage decreases as current increases.
How are fuel cells connected to obtain higher voltage?
They are connected in series.
What is the name of the arrangement connecting fuel cells in series and parallel?
A fuel cell stack.
How are fuel cells classified by electrolyte type?
As alkaline, phosphoric acid, polymer electrolyte membrane, molten carbonate, and solid oxide fuel cells.
What are the operating temperature classes of fuel cells?
Low (<150°C), medium (150–250°C), high (250–800°C), and very high (800–1100°C).
What electrolyte does a phosphoric acid fuel cell use?
Liquid phosphoric acid.
What is the overall chemical reaction in a PAFC?
At what temperature range do PAFCs operate?
About 150°C to 210°C.
What efficiency can PAFCs achieve in electricity-and-heat cogeneration?
85% efficiency.
What does an alkaline fuel cell consume and produce?
Consumes hydrogen and pure oxygen; produces potable water, heat, and electricity.
What is the net reaction in an alkaline fuel cell?
What electrolyte and electrodes does a polymer electrolyte membrane fuel cell use?
A polymeric membrane electrolyte and porous carbon electrodes with platinum catalyst.
Where do protons move in PEM fuel cells and what do they produce at the cathode?
Protons move through the electrolyte to the cathode to produce water and heat.
What are the operating temperature and key performance features of PEM fuel cells?
They operate at about 80°C, start quickly, have high power density, and low weight and volume.
What defines a direct methanol fuel cell compared to a PEM fuel cell?
It uses a polymer membrane and a platinum–ruthenium anode catalyst to extract hydrogen from liquid methanol.
What happens at the anode and cathode in a direct methanol fuel cell?
Methanol is oxidized and water consumed at the anode; oxygen reacts at the cathode to produce water.
How do protons and electrons move in a direct methanol fuel cell?
Protons cross the membrane; electrons pass through the external circuit.
What electrolyte does a molten carbonate fuel cell use?
A molten carbonate salt.
Which ions travel through the electrolyte to the anode in MCFCs?
Negative carbonate ions.
At what temperature do MCFCs operate?
650°C and above.
What is a solid oxide fuel cell?
An electrochemical device with a solid oxide or ceramic electrolyte producing electricity from fuel oxidation.
What ions do SOFCs conduct through their electrolyte?
Negatively charged oxygen ions.
What fuels can SOFCs internally reform?
Methane, propane, and butane.
Where is fuel-cell voltage regulation best for practical operation?
In the BC region where output voltage is about 0.6 V to 0.8 V.
Why do terminal voltage and efficiency decrease as a fuel cell is loaded?
Because of activation, resistance, and concentration polarisation.
What two types of diffusion cause concentration polarisation?
Slow diffusion in the electrolyte and slow reactant or product diffusion through porous electrodes.
What are the main charge carriers in PEMFC and PAFC fuel cells?
H+ ions.
Which ion is the main charge carrier in AFC fuel cells?
OH− ions.
What is the electrical efficiency range of SOFC fuel cells?
50% to 65%.
How long can fuel cells produce electricity?
Continuously as long as fuel and oxygen or air are supplied.
How long can batteries supply electricity?
Only while their internal chemical reaction persists.
Who developed the first fuel cell and in which year?
William Grove in 1838.
What materials did William Grove use for the first fuel cell?
Sheet iron, copper, porcelain plates, copper sulfate solution, and dilute acid.
Which fuels and oxidants classify fuel cells?
Hydrogen–oxygen, hydrogen-rich gas–air, hydrazine–oxygen or hydrogen peroxide, ammonia–air, synthesis gas–air, and hydrocarbon gas–air.
How are fuel cells classified by application?
As space, vehicle propulsion, submarine, defense, and commercial fuel cells.
How are fuel cells classified by electrolyte chemistry?
As acidic, alkaline, or neutral fuel cells.
What is the composition of PAFC electrolyte and electrode catalyst?
Highly concentrated phosphoric acid in silicon carbide matrix with platinum catalyst on carbon-paper electrodes.
Why are AFCs easily poisoned by carbon dioxide?
Because CO2 reacts with KOH to form potassium carbonate, increasing resistance.
What inputs do PEM fuel cells require and for which applications are they suitable?
They require hydrogen, oxygen from air, and water, suitable for cars, buildings, and smaller uses.
What are the operating temperature range and main advantages of DMFCs?
They operate from 60°C to 130°C; methanol's high energy density and ease of transport are advantages despite low efficiency.
What is the chemical reaction for internal reforming in an MCFC?
.
What efficiency can SOFCs reach and what catalyst need do they eliminate?
About 60% efficiency and no need for precious-metal catalysts.
When is activation polarisation significant in a fuel cell?
At low current density.
How can activation polarisation be reduced?
By using an effective electrochemical catalyst or increasing operating temperature.
What causes resistance polarisation in fuel cells?
Electrolyte resistance and electrode–electrolyte contact resistance.
How can resistance polarisation be reduced?
With higher-conductivity electrolyte, higher temperature, and suitable electrolyte shape and spacing.
Name three applications of fuel cells in transportation and defense.
Space systems, vehicle propulsion, and submarines.
Which navy used fuel-cell propulsion in a Type 212 submarine?
The German Navy.
In which year did Toyota introduce the Mirai fuel-cell vehicle in Japan?
2014.
Test your knowledge with 25 questions on Fuel Cell Technology.
1. What distinguishes a fuel cell from a battery in the way reactants are used?
2. A device must operate while hydrogen and air are supplied from external sources; which characteristic identifies it as a fuel cell rather than a battery?
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