Quiz: Fuel Cell Technology — 25 questions

1. What distinguishes a fuel cell from a battery in the way reactants are used?

A. A fuel cell converts electricity into chemical energy during normal operation

B. A fuel cell stores all reactants inside the device before operation

C. A fuel cell receives reactants continuously from outside the device

D. A fuel cell generates electricity through mechanical motion of its electrodes

Answer: (C)

Explanation

A fuel cell converts chemical energy from continuously supplied fuel and oxidant into electricity. The most plausible alternative is incorrect because storing reacting chemicals internally describes a battery more closely.

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?

A. It produces electricity through a reaction that cannot involve oxygen

B. It relies on chemicals sealed inside the device to sustain its reaction

C. It depends on externally supplied reactants to sustain its reaction

D. It generates electromotive force without requiring chemical reactants

Answer: (C)

Explanation

Fuel cells require a continuous external supply of fuel and oxygen or air. The strongest distractor describes a battery, whose reacting chemicals are already contained within it.

3. How does a fuel cell generate electricity while keeping ion and electron transport separate?

A. Its anode, electrolyte, and cathode direct ions and electrons through different paths

B. Its cathode produces electricity without participation from the electrolyte

C. Its anode blocks ions while the cathode carries electrons through the electrolyte

D. Its electrolyte sends ions and electrons together from the anode to the cathode

Answer: (A)

Explanation

The anode, electrolyte, and cathode establish separate paths for ion transport and electron transport. The most plausible distractor is wrong because the electrolyte transports ions while preventing electron passage.

4. What transport property must the electrolyte have in a fuel cell?

A. It blocks both ions and electrons to isolate the electrodes

B. It allows ions to pass while preventing electrons from passing

C. It carries ions and electrons together between the electrodes

D. It allows electrons to pass while preventing ions from passing

Answer: (B)

Explanation

The electrolyte is designed for ion conduction but electron insulation, forcing electrons through the external circuit. The closest distractor reverses these transport roles.

5. What voltage behavior is expected from a typical fuel cell operating at full rated load?

A. It produces about 1.5–2.0 V, with voltage increasing as current rises

B. It produces about 0.1–0.2 V, with voltage remaining constant as current rises

C. It produces about 3.0–4.0 V, with voltage decreasing as current falls

D. It produces about 0.6–0.7 V, with voltage decreasing as current rises

Answer: (D)

Explanation

A typical fuel cell delivers approximately 0.6–0.7 V at full rated load, and its voltage falls as current increases. The most plausible alternative uses a familiar battery-like voltage range but gives the wrong characteristic voltage.

6. How should individual fuel cells be connected to form a stack that provides both higher voltage and higher current?

A. Use parallel connections for higher voltage and series connections for higher current

B. Use parallel connections to increase neither voltage nor current significantly

C. Use series connections to increase both voltage and current together

D. Use series connections for higher voltage and parallel connections for higher current

Answer: (D)

Explanation

Series connections add cell voltages, while parallel connections increase the available current; the combined arrangement is called a fuel cell stack. The most plausible distractor reverses the functions of series and parallel connections.

7. Which classification groups fuel cells according to the electrolyte they use?

A. Alkaline, phosphoric acid, polymer electrolyte membrane, molten carbonate, and solid oxide

B. Space, vehicle propulsion, submarine, defense, and commercial fuel cells

C. Low-temperature, medium-temperature, high-temperature, and very-high-temperature fuel cells

D. Hydrogen–oxygen, hydrogen-rich gas–air, ammonia–air, synthesis gas–air, and hydrocarbon gas–air

Answer: (A)

Explanation

Electrolyte-based classification includes alkaline, phosphoric acid, polymer electrolyte membrane or solid polymer, molten carbonate, and solid oxide fuel cells. The closest distractor lists fuel-and-oxidant combinations rather than electrolyte types.

8. A fuel cell operates at 900°C; which operating-temperature category applies?

A. Very high temperature, from 800°C to 1100°C

B. Medium temperature, from 150°C to 250°C

C. High temperature, from 250°C to 800°C

D. Low temperature, below 150°C

Answer: (A)

Explanation

An operating temperature of 900°C falls within the very-high-temperature range of 800°C to 1100°C. The most plausible distractor is the high-temperature category, but that range ends at 800°C.

9. Which electrolyte and historical characteristic describe a phosphoric acid fuel cell?

A. Liquid phosphoric acid, and it was the first fuel-cell type commercialized

B. Liquid phosphoric acid, and it was developed after alkaline cells

C. Solid oxide ceramic, and it was the first fuel-cell type commercialized

D. Potassium hydroxide solution, and it was the first fuel-cell type commercialized

Answer: (A)

Explanation

A PAFC uses liquid phosphoric acid as its electrolyte and was the first fuel-cell type to be commercialized. Potassium hydroxide identifies an alkaline fuel cell, while solid oxide identifies a different fuel-cell family.

10. Which overall reaction represents the operation of a phosphoric acid fuel cell?

A. $4H^+ + 4e^- \rightarrow 2H_2$

B. $H_2 + O_2 \rightarrow H_2O_2$

C. $2H_2 + O_2 \rightarrow 2H_2O$

D. $2H_2O \rightarrow 2H_2 + O_2$

Answer: (C)

Explanation

The PAFC combines hydrogen and oxygen to form water according to $2H_2 + O_2 \rightarrow 2H_2O$. The reverse equation describes water splitting, while the other choices represent partial or different reactions.

11. Why are phosphoric acid fuel cells particularly suitable for stationary power generation with cogeneration?

A. They operate near 1000°C and conduct oxygen ions through a ceramic electrolyte

B. They operate above 650°C and internally reform methane without an external reformer

C. They operate near 80°C and provide high power density for lightweight mobile systems

D. They operate around 150–210°C and can reach about 85% efficiency when electricity and heat are combined

Answer: (D)

Explanation

PAFCs operate at about 150–210°C and can achieve roughly 85% efficiency in electricity-and-heat cogeneration, supporting stationary installations. The other descriptions correspond to PEMFC or high-temperature fuel-cell characteristics.

12. In an alkaline fuel cell, which reaction occurs at the anode?

A. $2H_2 \rightarrow 4H^+ + 4e^-$

B. $O_2 + 2H_2O + 4e^- \rightarrow 4OH^-$

C. $O_2 + 4H^+ + 4e^- \rightarrow 2H_2O$

D. $2H_2 + 4OH^- \rightarrow 4H_2O + 4e^-$

Answer: (D)

Explanation

At the AFC anode, hydrogen reacts with hydroxide ions to form water and release electrons: $2H_2 + 4OH^- \rightarrow 4H_2O + 4e^-$. The second equation is the AFC cathode reaction, while the remaining equations are associated with PAFC electrode chemistry.

13. What distinguishes the electrolyte and electrodes of a polymer electrolyte membrane fuel cell?

A. A solid oxide electrolyte with metallic electrodes containing non-precious catalysts

B. A molten carbonate electrolyte with porous ceramic electrodes containing nickel

C. A polymeric membrane electrolyte with porous carbon electrodes containing platinum

D. A liquid phosphoric-acid electrolyte with carbon-paper electrodes containing platinum

Answer: (C)

Explanation

A PEMFC uses a polymer membrane electrolyte and porous carbon electrodes containing platinum catalyst. Liquid phosphoric acid belongs to PAFCs, while molten carbonate and solid oxide electrolytes characterize high-temperature cells.

14. In a PEM fuel cell, how do protons and electrons reach the cathode?

A. Both protons and electrons cross the membrane to reach the cathode

B. Protons cross the membrane, while electrons travel through the external circuit

C. Protons travel through the external circuit, while electrons cross the membrane

D. Both protons and electrons travel through the external circuit to reach the cathode

Answer: (B)

Explanation

The PEM membrane conducts protons to the cathode, whereas electrons move through the external circuit. At the cathode, the protons and electrons combine with oxygen to produce water and heat.

15. Which combination best explains why PEM fuel cells are attractive for lightweight mobile applications?

A. Operation near 1000°C, ceramic electrolyte conduction, and substantial thermal inertia

B. Operation near 80°C, rapid startup, high power density, and low weight and volume

C. Operation near 200°C, slow startup, moderate power density, and high system volume

D. Operation above 650°C, internal methane reforming, and non-precious catalysts

Answer: (B)

Explanation

PEM fuel cells operate at about 80°C, start quickly, and provide high power density with low weight and volume. The other combinations describe characteristics of PAFCs or high-temperature fuel cells rather than PEMFCs.

16. What is the defining fuel-processing feature of a direct methanol fuel cell?

A. It oxidizes coal-derived gas at a molten-carbonate anode using a nickel catalyst

B. It separates hydrogen from water at a ceramic cathode using an oxygen-ion electrolyte

C. It reforms natural gas externally before sending hydrogen to a phosphoric-acid electrolyte

D. It extracts hydrogen directly from liquid methanol using a platinum–ruthenium anode catalyst

Answer: (D)

Explanation

A DMFC is a PEM-like cell that extracts hydrogen directly from liquid methanol, using a platinum–ruthenium anode catalyst. The other choices describe fuel processing or electrolyte systems associated with different fuel-cell types.

17. Which electrolyte and fuel sources characterize a molten carbonate fuel cell?

A. Liquid phosphoric acid, with pure hydrogen as the required fuel source

B. A polymer membrane, with liquid methanol as the required fuel source

C. A molten carbonate salt, with possible fuels including coal-derived gases, methane, or natural gas

D. A solid oxide ceramic, with possible fuels including coal-derived gases, methane, or natural gas

Answer: (C)

Explanation

An MCFC uses molten carbonate salt as its electrolyte and can be fueled by coal-derived gases, methane, or natural gas. A solid oxide electrolyte identifies an SOFC, while polymer and phosphoric-acid electrolytes identify other cell types.

18. What happens to carbonate ions in a molten carbonate fuel cell?

A. They move through the electrolyte to the anode, where they react with hydrogen to form water and electrons

B. They move through the electrolyte to the cathode, where they react with oxygen to form hydrogen and electrons

C. They move through the electrolyte to the anode, where they react with methane to form oxygen and protons

D. They remain in the electrolyte while hydrogen crosses to the cathode and combines with oxygen

Answer: (A)

Explanation

Negative carbonate ions travel toward the MCFC anode, where they combine with hydrogen and generate water and electrons. Oxygen ions moving toward the anode are characteristic of SOFC operation, not MCFC operation.

19. Which combination correctly describes molten carbonate fuel cells?

A. They operate at 150–210°C, use concentrated phosphoric acid, and reach about 42% electrical efficiency

B. They operate near 1000°C, conduct oxygen ions, and internally reform several light hydrocarbons

C. They operate at 650°C or higher, can reach about 60% efficiency, and use non-precious catalysts without an external reformer

D. They operate near 80°C, start quickly, and use platinum catalysts in a polymer membrane

Answer: (C)

Explanation

MCFCs operate at 650°C and above, can reach approximately 60% efficiency, use non-precious catalysts, and do not require an external reformer. The other options describe PEMFCs, PAFCs, or SOFCs.

20. Which feature distinguishes a solid oxide fuel cell from a molten carbonate fuel cell?

A. An SOFC conducts negatively charged oxygen ions and can internally reform methane, propane, and butane

B. An SOFC conducts hydroxide ions through an alkaline electrolyte and produces potable water

C. An SOFC conducts carbonate ions and requires an external reformer for methane-based fuels

D. An SOFC conducts protons through a polymer membrane and operates near 80°C

Answer: (A)

Explanation

SOFCs conduct negatively charged oxygen ions through a solid oxide electrolyte and can internally reform methane, propane, and butane. Carbonate-ion transport belongs to MCFCs, while polymer membranes and hydroxide electrolytes belong to other fuel-cell types.

21. In which operating region does a fuel cell typically achieve its best voltage regulation, with an output voltage of about $0.6\text{ V}$ to $0.8\text{ V}$?

A. The BC region between the low- and high-current extremes

B. The transition region immediately after activation begins

C. The high-current region near maximum power output

D. The low-current region near open-circuit operation

Answer: (A)

Explanation

The BC region provides the most stable voltage regulation and typically produces about $0.6\text{ V}$ to $0.8\text{ V}$. The low- and high-current regions are less suitable because their voltage regulation is poorer.

22. What happens to a fuel cell's terminal voltage and efficiency as the cell is increasingly loaded?

A. Voltage remains fixed while efficiency decreases because losses affect power alone

B. Both increase because reactant consumption improves electrochemical conversion

C. Both decrease because activation, resistance, and concentration polarisation increase

D. Voltage rises while efficiency falls because current production becomes stronger

Answer: (C)

Explanation

Loading causes voltage and efficiency to fall from the theoretical open-circuit condition because of activation, resistance, and concentration polarisation. The idea that voltage rises with loading confuses useful current production with the increasing internal losses.

23. Which example correctly distinguishes the two forms of concentration polarisation in a fuel cell?

A. Electrolyte polarisation concerns electron flow, whereas gas-side polarisation concerns external circuit resistance

B. Electrolyte polarisation involves slow diffusion in the electrolyte, whereas gas-side polarisation involves diffusion through porous electrodes

C. Electrolyte polarisation comes from electrode contacts, whereas gas-side polarisation comes from catalyst activation

D. Electrolyte polarisation occurs at high temperature, whereas gas-side polarisation occurs at low temperature

Answer: (B)

Explanation

Concentration polarisation includes slow diffusion within the electrolyte and slow reactant or product diffusion through porous electrodes. Electrode contact resistance and catalyst activation are different loss mechanisms, not the two forms of concentration polarisation.

24. Which pairing correctly identifies the main charge carriers in PEMFC, PAFC, and AFC systems?

A. O^2− in PEMFC and PAFC, and CO3^2− in AFC

B. OH− in PEMFC and PAFC, and H+ in AFC

C. H+ in PEMFC and PAFC, and OH− in AFC

D. CO3^2− in PEMFC and PAFC, and O^2− in AFC

Answer: (C)

Explanation

PEMFC and PAFC conduct H+, while AFC conducts OH−. Carbonate and oxide ions are associated with MCFC and SOFC systems, respectively, rather than with these three cells.

25. Which fuel-cell type has the highest listed electrical-efficiency range among the systems compared?

A. SOFC, with an efficiency range of 50% to 65%

B. PAFC, with an efficiency range of 40% to 50%

C. AFC, with an efficiency range of 40% to 60%

D. MCFC, with an efficiency range of 50% to 60%

Answer: (A)

Explanation

SOFC has the highest listed range, from 50% to 65%. MCFC reaches 50% to 60%, while AFC and PAFC have lower upper limits of 60% and 50%, respectively.