Q.1 What is the most common type of fuel cell used in automotive applications?
Alkaline Fuel Cell (AFC)
Proton Exchange Membrane Fuel Cell (PEMFC)
Molten Carbonate Fuel Cell (MCFC)
Solid Oxide Fuel Cell (SOFC)
Explanation - PEMFCs operate at low temperatures, have high power density, and can be quickly started, making them suitable for vehicles.
Correct answer is: Proton Exchange Membrane Fuel Cell (PEMFC)
Q.2 In a hydrogen fuel cell, hydrogen is oxidized at the anode to produce:
O₂ and electrons
Water and electrons
Hydrogen ions (protons) and electrons
Carbon dioxide and electrons
Explanation - At the anode, H₂ → 2H⁺ + 2e⁻; the protons travel through the electrolyte while electrons go through the external circuit.
Correct answer is: Hydrogen ions (protons) and electrons
Q.3 Which electrolyte is used in a Solid Oxide Fuel Cell (SOFC)?
Liquid potassium hydroxide
Solid ceramic oxide
Phosphoric acid
Nafion polymer
Explanation - SOFCs use a dense, oxygen‑ion conducting ceramic (e.g., YSZ) as the electrolyte, allowing operation at 600‑1000 °C.
Correct answer is: Solid ceramic oxide
Q.4 The overall reaction of a hydrogen fuel cell combining hydrogen and oxygen is:
2H₂ + O₂ → 2H₂O
H₂ + ½O₂ → H₂O
H₂ + O₂ → 2OH⁻
2H₂ + 2O₂ → 2H₂O₂
Explanation - Two molecules of hydrogen react with one molecule of oxygen to produce two molecules of water, releasing electrical energy.
Correct answer is: 2H₂ + O₂ → 2H₂O
Q.5 Which of the following is NOT an advantage of fuel cells over internal combustion engines?
Higher efficiency
Zero tailpipe emissions (when using hydrogen)
Fast refueling time
Higher noise levels
Explanation - Fuel cells operate quietly; higher noise is a characteristic of combustion engines, not fuel cells.
Correct answer is: Higher noise levels
Q.6 What is the primary by‑product of a PEM fuel cell when pure hydrogen is used as fuel?
Carbon dioxide
Methane
Water vapor
Nitrogen gas
Explanation - Hydrogen reacts with oxygen to form water; no carbon‑containing fuels are present, so CO₂ is not produced.
Correct answer is: Water vapor
Q.7 Which component of a fuel cell stack controls the flow of reactant gases to the electrodes?
Bipolar plate
Catalyst layer
Membrane electrode assembly (MEA)
Current collector
Explanation - Bipolar plates have flow channels that distribute fuel and oxidant uniformly over the electrode surfaces.
Correct answer is: Bipolar plate
Q.8 In an alkaline fuel cell (AFC), the electrolyte is:
Sulfuric acid
Potassium hydroxide solution
Phosphoric acid
Nafion polymer
Explanation - AFCs use an aqueous KOH solution as the electrolyte, allowing hydroxide ions (OH⁻) to conduct.
Correct answer is: Potassium hydroxide solution
Q.9 What is the theoretical maximum efficiency (based on Gibbs free energy) of a hydrogen‑oxygen fuel cell at 25 °C?
50 %
60 %
70 %
80 %
Explanation - The theoretical efficiency η = ΔG/ΔH ≈ 237 kJ/mol ÷ 286 kJ/mol ≈ 83 % (rounded to 80 %).
Correct answer is: 80 %
Q.10 Which of the following fuels can be directly used in a molten carbonate fuel cell (MCFC) without reforming?
Pure hydrogen
Methane
Ammonia
Carbon monoxide
Explanation - MCFCs operate at high temperature and can oxidize CO directly; H₂ and CH₄ typically require reforming.
Correct answer is: Carbon monoxide
Q.11 The term "hydrogen economy" refers to:
A system where hydrogen replaces all fossil fuels in the world
A future energy system where hydrogen is a major carrier and storage medium
An economic model based on selling hydrogen as a commodity
A market where hydrogen is used only in industrial processes
Explanation - The hydrogen economy envisions hydrogen produced from renewable sources, stored, transported, and used for power, transport, and heating.
Correct answer is: A future energy system where hydrogen is a major carrier and storage medium
Q.12 Which material is commonly used as a catalyst in PEM fuel cells?
Platinum
Nickel
Copper
Iron
Explanation - Platinum provides high catalytic activity for both hydrogen oxidation and oxygen reduction in acidic PEM environments.
Correct answer is: Platinum
Q.13 What is the main challenge associated with hydrogen storage for fuel‑cell vehicles?
Hydrogen is toxic
Hydrogen has low energy density by volume
Hydrogen reacts explosively with metal parts
Hydrogen cannot be compressed
Explanation - Hydrogen is light, so storing enough of it in a small volume requires high pressures, low temperatures, or advanced materials.
Correct answer is: Hydrogen has low energy density by volume
Q.14 Which of the following processes produces hydrogen without emitting CO₂?
Steam methane reforming (SMR)
Coal gasification
Electrolysis of water using renewable electricity
Partial oxidation of natural gas
Explanation - When electricity from wind, solar, or hydro powers electrolysis, the only by‑product is oxygen, making the process carbon‑free.
Correct answer is: Electrolysis of water using renewable electricity
Q.15 In a fuel cell, the component that separates the anode and cathode while conducting ions is called:
Bipolar plate
Electrolyte membrane
Catalyst layer
Current collector
Explanation - The electrolyte (solid polymer membrane in PEMFCs) permits ion transport but blocks electrons, ensuring current flows through the external circuit.
Correct answer is: Electrolyte membrane
Q.16 Which of the following is a typical operating temperature range for a Proton Exchange Membrane Fuel Cell (PEMFC)?
-20 °C to 0 °C
0 °C to 30 °C
60 °C to 80 °C
400 °C to 600 °C
Explanation - PEMFCs generally operate between 60 °C and 80 °C, balancing membrane conductivity and water management.
Correct answer is: 60 °C to 80 °C
Q.17 What is the primary role of the catalyst in a fuel cell?
To store electrical charge
To increase the rate of electrochemical reactions
To conduct electrons across the cell
To separate hydrogen and oxygen gases
Explanation - Catalysts lower the activation energy for hydrogen oxidation and oxygen reduction, enabling the reactions to proceed quickly at lower temperatures.
Correct answer is: To increase the rate of electrochemical reactions
Q.18 Which fuel cell type operates at the highest temperature?
Alkaline Fuel Cell (AFC)
Phosphoric Acid Fuel Cell (PAFC)
Molten Carbonate Fuel Cell (MCFC)
Proton Exchange Membrane Fuel Cell (PEMFC)
Explanation - MCFCs work at 600–700 °C, higher than other common fuel cell types.
Correct answer is: Molten Carbonate Fuel Cell (MCFC)
Q.19 In a fuel cell system, the term "stack" refers to:
A single fuel cell unit
A series of fuel cells electrically connected in series
The storage tank for hydrogen
The cooling system for the cell
Explanation - Stacks combine multiple cells to increase voltage and power output; each cell contributes about 0.6–1 V.
Correct answer is: A series of fuel cells electrically connected in series
Q.20 Which method is commonly used to remove excess water from the cathode side of a PEM fuel cell?
Heating the cell to 200 °C
Using a porous carbon diffusion layer
Applying a vacuum pump
Integrating a water‑management gasket
Explanation - The diffusion layer allows water to be wicked away while still providing gas transport, preventing flooding.
Correct answer is: Using a porous carbon diffusion layer
Q.21 Hydrogen can be produced from natural gas through which process?
Photolysis
Steam methane reforming (SMR)
Electrolysis
Fermentation
Explanation - SMR reacts methane with steam at high temperature to generate hydrogen and carbon monoxide.
Correct answer is: Steam methane reforming (SMR)
Q.22 What is the main environmental benefit of using fuel cells powered by hydrogen produced via renewable electrolysis?
Elimination of water consumption
Zero greenhouse‑gas emissions during operation
Increased use of fossil fuels
Higher noise pollution
Explanation - When the hydrogen is made with renewable electricity, the only emission from the fuel cell is water vapor.
Correct answer is: Zero greenhouse‑gas emissions during operation
Q.23 Which of the following is a major drawback of solid oxide fuel cells (SOFCs) for mobile applications?
Low power density
Requirement of high operating temperature
Need for acidic electrolyte
Incompatibility with hydrogen fuel
Explanation - SOFCs need 600‑1000 °C to conduct oxygen ions, making rapid start‑up and lightweight packaging difficult for vehicles.
Correct answer is: Requirement of high operating temperature
Q.24 Which parameter directly influences the voltage loss due to concentration overpotential in a fuel cell?
Temperature of the cell
Rate of reactant supply
Thickness of the membrane
Catalyst surface area
Explanation - Concentration overpotential occurs when reactant diffusion cannot keep up with reaction rates; increasing supply reduces this loss.
Correct answer is: Rate of reactant supply
Q.25 The Nernst equation is used in fuel cells to:
Calculate the open‑circuit voltage based on temperature and pressure
Determine the membrane thickness
Predict catalyst degradation
Estimate water production rate
Explanation - The Nernst equation relates cell voltage to the activities (partial pressures) of reactants and products.
Correct answer is: Calculate the open‑circuit voltage based on temperature and pressure
Q.26 Which of the following is NOT a type of hydrogen storage technology?
Compressed gas cylinders
Liquid hydrogen tanks
Metal hydride storage
Lithium‑ion battery
Explanation - Lithium‑ion batteries store electrical energy, not hydrogen; the other three store hydrogen in different physical forms.
Correct answer is: Lithium‑ion battery
Q.27 In a PEM fuel cell, water management is critical because:
Too much water dilutes the hydrogen feed
Water freezes the electrolyte at low temperatures
Both dehydration and flooding can reduce performance
Water reacts with the catalyst and deactivates it
Explanation - The membrane needs sufficient hydration for proton conductivity, yet excess water can block gas flow and cause flooding.
Correct answer is: Both dehydration and flooding can reduce performance
Q.28 Which of the following statements about fuel cell efficiency is true?
Fuel cells are always more efficient than batteries
Fuel cells convert chemical energy directly to electrical energy with fewer losses
Fuel cells cannot operate at partial load
Fuel cells produce more CO₂ than internal combustion engines
Explanation - Because there is no combustion step, fuel cells avoid many thermodynamic losses associated with heat engines.
Correct answer is: Fuel cells convert chemical energy directly to electrical energy with fewer losses
Q.29 Which fuel cell type uses a liquid alkaline electrolyte?
Phosphoric Acid Fuel Cell (PAFC)
Alkaline Fuel Cell (AFC)
Solid Oxide Fuel Cell (SOFC)
Proton Exchange Membrane Fuel Cell (PEMFC)
Explanation - AFCs employ an aqueous potassium hydroxide (KOH) solution as the electrolyte.
Correct answer is: Alkaline Fuel Cell (AFC)
Q.30 The term "electrochemical reforming" in fuel cell technology refers to:
Direct conversion of methane to electricity in a fuel cell
Using electricity to split water into hydrogen and oxygen
Catalytic conversion of hydrocarbons to hydrogen within the fuel cell
Recycling spent fuel cell materials
Explanation - Electrochemical reforming generates hydrogen from fuels like methanol directly inside a fuel cell stack.
Correct answer is: Catalytic conversion of hydrocarbons to hydrogen within the fuel cell
Q.31 Which factor most strongly influences the cost of a PEM fuel cell system?
Price of platinum catalyst
Length of the bipolar plates
Size of the hydrogen storage tank
Thickness of the membrane
Explanation - Platinum accounts for a large portion of PEMFC cost; reducing its loading is a key research focus.
Correct answer is: Price of platinum catalyst
Q.32 When hydrogen is stored as a metal hydride, the hydrogen is released by:
Applying an electric current
Increasing temperature
Reducing pressure
Adding water
Explanation - Metal hydrides release hydrogen upon heating (desorption), a reversible process used in some storage systems.
Correct answer is: Increasing temperature
Q.33 What is the main advantage of a Direct Methanol Fuel Cell (DMFC) over a PEMFC?
Higher operating temperature
Uses liquid methanol directly as fuel, eliminating a reformer
Produces more electricity per unit fuel
Requires no catalyst
Explanation - DMFCs can run on methanol without a separate hydrogen production step, simplifying the system.
Correct answer is: Uses liquid methanol directly as fuel, eliminating a reformer
Q.34 Which of the following is a key challenge for large‑scale hydrogen distribution?
Hydrogen reacts violently with steel pipelines
Hydrogen embrittles many metals used in pipelines
Hydrogen cannot be liquefied
Hydrogen is heavier than air
Explanation - Hydrogen can cause embrittlement, reducing the mechanical strength of steel pipelines, requiring special materials or coatings.
Correct answer is: Hydrogen embrittles many metals used in pipelines
Q.35 In a fuel cell, the term "crossover" refers to:
Hydrogen leaking into the air intake
Oxygen permeating through the electrolyte to the anode
Fuel mixing with the coolant
Electric current leaking through the housing
Explanation - Crossover is the undesired diffusion of reactants through the membrane, reducing efficiency and potentially causing unwanted reactions.
Correct answer is: Oxygen permeating through the electrolyte to the anode
Q.36 Which renewable energy source is most commonly coupled with electrolyzers for green hydrogen production?
Geothermal
Nuclear
Wind and solar
Hydropower
Explanation - Wind turbines and solar PV provide abundant, variable electricity ideal for powering water electrolysis to make green hydrogen.
Correct answer is: Wind and solar
Q.37 What is the primary reason PEM fuel cells operate at low temperatures compared with SOFCs?
The polymer membrane degrades at high temperature
The catalyst melts above 100 °C
Hydrogen cannot be supplied at high temperature
Water management is easier at low temperature
Explanation - PEM membranes (e.g., Nafion) lose mechanical integrity and conductivity above ~120 °C.
Correct answer is: The polymer membrane degrades at high temperature
Q.38 Which of the following best describes the term "fuel cell stack efficiency"?
Ratio of electrical output to thermal input
Ratio of chemical energy of fuel to electrical energy produced
Ratio of hydrogen stored to hydrogen used
Ratio of catalyst mass to cell voltage
Explanation - Stack efficiency compares the usable electrical energy to the total chemical energy supplied by the fuel.
Correct answer is: Ratio of chemical energy of fuel to electrical energy produced
Q.39 Which fuel cell type can directly use carbon monoxide (CO) as a fuel without a reformer?
PEMFC
AFC
MCFC
SOFC
Explanation - Molten carbonate fuel cells can oxidize CO directly due to their high operating temperature.
Correct answer is: MCFC
Q.40 During the operation of a PEM fuel cell, water is produced at which electrode?
Anode
Cathode
Both anode and cathode equally
Neither, water is only formed outside the cell
Explanation - Oxygen reduction at the cathode combines with protons arriving from the membrane to form water.
Correct answer is: Cathode
Q.41 A major advantage of using a fuel cell over a battery for stationary power is:
Higher energy density and longer continuous operation
Zero maintenance requirements
Instantaneous power output without any start‑up time
Ability to store electricity without any fuel
Explanation - Fuel cells can run continuously as long as fuel is supplied, whereas batteries are limited by stored chemical energy.
Correct answer is: Higher energy density and longer continuous operation
Q.42 In a hydrogen fuel cell system, the term "regenerative fuel cell" refers to:
A fuel cell that also works as an electrolyzer to store excess electricity
A fuel cell that recycles its own waste water
A fuel cell that can self‑repair its catalyst
A fuel cell that operates in both high and low temperatures
Explanation - Regenerative fuel cells can run in reverse mode, using electricity to generate hydrogen (electrolysis).
Correct answer is: A fuel cell that also works as an electrolyzer to store excess electricity
Q.43 Which of the following is a common method for measuring the performance of a fuel cell?
Voltage‑current (V‑I) polarization curve
Thermal imaging
Acoustic emission testing
Magnetic resonance imaging
Explanation - Polarization curves plot cell voltage against current density to assess losses and efficiency.
Correct answer is: Voltage‑current (V‑I) polarization curve
Q.44 When using hydrogen as a fuel, the term "gray hydrogen" indicates:
Hydrogen produced from nuclear power
Hydrogen produced via electrolysis using renewable energy
Hydrogen produced from natural gas with CO₂ emissions
Hydrogen stored in underground caverns
Explanation - Gray hydrogen is generated by steam methane reforming without carbon capture, resulting in CO₂ release.
Correct answer is: Hydrogen produced from natural gas with CO₂ emissions
Q.45 Which safety concern is most associated with high‑pressure hydrogen storage tanks?
Corrosion of the tank material
Hydrogen flame flashback
Leakage leading to explosive mixtures
Radiation emission
Explanation - Hydrogen is highly flammable; leaks can create ignitable mixtures with air.
Correct answer is: Leakage leading to explosive mixtures
Q.46 The electrochemical reaction at the cathode of a PEM fuel cell reduces oxygen to form:
Hydrogen gas
Water and electrons
Hydrogen ions
Carbon dioxide
Explanation - O₂ + 4H⁺ + 4e⁻ → 2H₂O; electrons travel through the external circuit producing electricity.
Correct answer is: Water and electrons
Q.47 Which factor most directly determines the power density (W cm⁻²) of a fuel cell?
Thickness of the bipolar plates
Catalyst loading per unit area
Operating temperature
Pressure of the reactant gases
Explanation - Higher catalyst loading improves reaction rates, increasing current density and thus power density.
Correct answer is: Catalyst loading per unit area
Q.48 What is the purpose of humidifying the inlet gases in a PEM fuel cell?
To increase the pressure of the gases
To keep the membrane hydrated for proton conductivity
To reduce the temperature of the cell
To clean the gases from impurities
Explanation - A hydrated membrane conducts protons efficiently; dry gases would dehydrate it, raising resistance.
Correct answer is: To keep the membrane hydrated for proton conductivity
Q.49 Which of the following fuels can be directly used in a Direct Formic Acid Fuel Cell (DFAFC)?
Methanol
Formic acid
Hydrogen
Ethanol
Explanation - DFAFCs oxidize formic acid directly at the anode, offering high power density and low crossover.
Correct answer is: Formic acid
Q.50 In the context of hydrogen production, "blue hydrogen" means:
Hydrogen generated by water electrolysis using nuclear power
Hydrogen produced from natural gas with carbon capture and storage (CCS)
Hydrogen stored in blue‑colored containers
Hydrogen made from biomass
Explanation - Blue hydrogen captures the CO₂ emitted during SMR, reducing its carbon footprint.
Correct answer is: Hydrogen produced from natural gas with carbon capture and storage (CCS)
Q.51 Which component in a fuel cell stack provides electrical connection between adjacent cells?
Gas diffusion layer
Current collector
Catalyst coated membrane
Sealing gasket
Explanation - Current collectors (often part of the bipolar plates) collect and conduct electrons from one cell to the next.
Correct answer is: Current collector
Q.52 A key advantage of using molten carbonate fuel cells for stationary power is:
Operation at ambient temperature
Ability to use CO₂ as a reactant, improving overall efficiency
No need for a catalyst
Instant start‑up
Explanation - MCFCs incorporate CO₂ in the electrolyte, allowing internal CO₂ recycling and higher overall efficiency.
Correct answer is: Ability to use CO₂ as a reactant, improving overall efficiency
Q.53 Which of the following is NOT a typical degradation mechanism for PEM fuel cells?
Catalyst poisoning by carbon monoxide
Membrane thinning due to chemical attack
Electrode delamination from thermal cycling
Electrolyte boiling
Explanation - PEM fuel cells use a solid polymer membrane; boiling does not occur. The other options are common degradation modes.
Correct answer is: Electrolyte boiling
Q.54 What is the main function of the gas diffusion layer (GDL) in a fuel cell?
To conduct electrons and facilitate gas transport to the catalyst layer
To store excess hydrogen
To act as the primary electrolyte
To provide structural support only
Explanation - The GDL is porous, conductive, and spreads reactant gases evenly across the catalyst surface while removing water.
Correct answer is: To conduct electrons and facilitate gas transport to the catalyst layer
Q.55 In a fuel cell, the term "ohmic loss" refers to:
Losses due to activation energy of reactions
Losses caused by resistance of ion and electron pathways
Losses from fuel crossover
Losses due to heat generation
Explanation - Ohmic losses arise from the resistance of the electrolyte, electrodes, and interconnects.
Correct answer is: Losses caused by resistance of ion and electron pathways
Q.56 Which of the following best describes a 'hydrogen fuel cell hybrid vehicle'?
A vehicle that uses both hydrogen fuel cells and a gasoline engine
A vehicle that combines a fuel cell with a battery or supercapacitor for energy storage
A vehicle that runs on both hydrogen and diesel simultaneously
A vehicle that uses hydrogen only for heating, not propulsion
Explanation - Hybrid designs store excess electricity from the fuel cell for regenerative braking and to meet peak power demands.
Correct answer is: A vehicle that combines a fuel cell with a battery or supercapacitor for energy storage
Q.57 What is the principal chemical form of hydrogen stored in liquid organic hydrogen carriers (LOHCs)?
Molecular H₂ dissolved in oil
Hydrogen chemically bound to organic molecules
Hydrogen as a solid metal hydride
Atomic hydrogen trapped in carbon nanotubes
Explanation - LOHCs store hydrogen by hydrogenation of organic compounds, releasing it upon catalytic dehydrogenation.
Correct answer is: Hydrogen chemically bound to organic molecules
Q.58 The main reason why fuel cells are considered 'silent' power sources is because:
They use no moving parts that generate mechanical noise
Hydrogen combustion produces no sound
The electricity generated is inaudible
They operate underwater
Explanation - Fuel cells rely on electrochemical reactions, not mechanical motion, leading to very low acoustic emissions.
Correct answer is: They use no moving parts that generate mechanical noise
Q.59 Which of the following statements about hydrogen embrittlement is correct?
It strengthens steel structures
It occurs only at cryogenic temperatures
It reduces ductility and can cause cracking in metals
It is beneficial for fuel cell durability
Explanation - Hydrogen atoms diffuse into metal lattices, causing loss of toughness and potential failure.
Correct answer is: It reduces ductility and can cause cracking in metals
Q.60 In the context of fuel cells, the term "open‑circuit voltage" (OCV) refers to:
The voltage when the cell is delivering maximum current
The voltage measured when no external load is connected
The voltage drop across the electrolyte
The voltage needed to start the cell
Explanation - OCV is the maximum theoretical voltage of the cell under no current draw, determined by thermodynamics.
Correct answer is: The voltage measured when no external load is connected
Q.61 Which type of fuel cell is most suited for portable electronic devices due to its compact size and low operating temperature?
Solid Oxide Fuel Cell (SOFC)
Molten Carbonate Fuel Cell (MCFC)
Proton Exchange Membrane Fuel Cell (PEMFC)
Phosphoric Acid Fuel Cell (PAFC)
Explanation - PEMFCs are lightweight, operate at 60‑80 °C, and can be made small enough for handheld electronics.
Correct answer is: Proton Exchange Membrane Fuel Cell (PEMFC)
Q.62 Which renewable energy source currently provides the largest share of electricity used for green hydrogen production worldwide?
Solar photovoltaic
Wind power
Geothermal
Biomass
Explanation - Wind farms have been the predominant source feeding electrolyzers for green hydrogen projects due to high capacity factors and low cost.
Correct answer is: Wind power
Q.63 In a fuel cell, the term "catalyst layer thickness" most directly influences:
The amount of water produced
The rate of electrochemical reactions
The voltage of the external circuit
The weight of the fuel cell
Explanation - A thicker catalyst layer provides more active surface area, enhancing reaction rates, but can also increase mass transport resistance.
Correct answer is: The rate of electrochemical reactions
Q.64 Which of the following is a typical product of water electrolysis besides hydrogen?
Methane
Carbon monoxide
Oxygen
Nitrogen
Explanation - Electrolysis splits water into H₂ and O₂ in a 2:1 molar ratio.
Correct answer is: Oxygen
Q.65 The main advantage of using a proton‑conducting ceramic electrolyte (PCFC) over a traditional PEM is:
Higher operating temperature allowing use of hydrocarbon fuels
Lower material cost
Operation at cryogenic temperatures
Elimination of catalyst requirement
Explanation - PCFCs operate at ~600 °C, enabling internal reforming of hydrocarbons and reducing catalyst poisoning.
Correct answer is: Higher operating temperature allowing use of hydrocarbon fuels
Q.66 Which of these processes is used to increase the purity of hydrogen produced from steam methane reforming (SMR)?
Pressure swing adsorption (PSA)
Distillation
Magnetic separation
Centrifugation
Explanation - PSA removes CO₂, CO, and other impurities, yielding high‑purity H₂ for fuel cells.
Correct answer is: Pressure swing adsorption (PSA)
Q.67 Which phenomenon limits the maximum current density of a fuel cell at high load?
Activation overpotential
Ohmic loss
Mass transport (concentration) overpotential
Thermal runaway
Explanation - At high current, reactant gases cannot diffuse fast enough to the reaction sites, causing voltage loss.
Correct answer is: Mass transport (concentration) overpotential
Q.68 In a fuel cell system, the term "balance‑of‑plant" (BoP) refers to:
The stack of fuel cells only
All auxiliary components such as pumps, compressors, heat exchangers, and control electronics
The hydrogen fuel tank only
The software algorithm used for control
Explanation - BoP includes everything needed to operate the fuel cell aside from the stack itself.
Correct answer is: All auxiliary components such as pumps, compressors, heat exchangers, and control electronics
Q.69 Which of the following is a key reason for using high‑pressure hydrogen in fuel‑cell vehicles?
To increase the chemical reactivity of hydrogen
To reduce the volume of hydrogen storage tanks
To lower the temperature of the fuel cell
To eliminate the need for a catalyst
Explanation - Compressing hydrogen to 350–700 bar allows more fuel to be stored in a given space, extending vehicle range.
Correct answer is: To reduce the volume of hydrogen storage tanks
Q.70 Which fuel cell type uses phosphoric acid as its electrolyte?
Alkaline Fuel Cell (AFC)
Phosphoric Acid Fuel Cell (PAFC)
Molten Carbonate Fuel Cell (MCFC)
Solid Oxide Fuel Cell (SOFC)
Explanation - PAFCs employ liquid phosphoric acid impregnated in a silica matrix as the electrolyte.
Correct answer is: Phosphoric Acid Fuel Cell (PAFC)
Q.71 Which of the following best describes the term "fuel cell efficiency at partial load"?
Efficiency is always higher at partial load than at full load
Efficiency decreases because activation losses become more significant
Efficiency remains constant regardless of load
Efficiency is unrelated to load conditions
Explanation - At low current densities, activation overpotential dominates, reducing the voltage and thus efficiency.
Correct answer is: Efficiency decreases because activation losses become more significant
Q.72 In the context of hydrogen production, the term "electrolyte degradation" typically refers to:
Loss of membrane conductivity due to chemical attack
Physical cracking of the bipolar plates
Corrosion of the hydrogen storage tank
Reduction of catalyst activity
Explanation - Electrolyte membranes can degrade via radicals, mechanical stress, or dehydration, reducing proton conductivity.
Correct answer is: Loss of membrane conductivity due to chemical attack
Q.73 Which of the following is a direct advantage of using fuel cells for backup power in data centers?
Zero emissions even if the grid fails
Instantaneous start‑up within milliseconds
High energy density compared to batteries
Long uninterrupted run time without fuel
Explanation - Fuel cells can provide clean, silent power during outages, avoiding diesel generator emissions.
Correct answer is: Zero emissions even if the grid fails
Q.74 Which method is commonly employed to recycle spent PEM fuel cell membranes?
Thermal incineration
Mechanical shredding and landfill
Chemical recovery of platinum and polymer recycling
Direct reuse without treatment
Explanation - Spent membranes can be processed to recover valuable platinum catalyst and the polymer can be repurposed, reducing waste.
Correct answer is: Chemical recovery of platinum and polymer recycling
Q.75 Which fuel cell technology is most widely used in stationary combined heat and power (CHP) systems today?
Alkaline Fuel Cell (AFC)
Proton Exchange Membrane Fuel Cell (PEMFC)
Solid Oxide Fuel Cell (SOFC)
Molten Carbonate Fuel Cell (MCFC)
Explanation - SOFCs operate at high temperature, allowing efficient electricity generation and useful waste heat for CHP.
Correct answer is: Solid Oxide Fuel Cell (SOFC)
Q.76 The primary reason that fuel cells have a higher specific power (W kg⁻¹) compared with batteries is:
They use lighter metals in construction
They directly convert chemical energy to electricity without intermediate conversion steps
They have built‑in energy storage
They operate at cryogenic temperatures
Explanation - Fuel cells avoid the charge‑discharge cycles of batteries, providing higher power per unit mass.
Correct answer is: They directly convert chemical energy to electricity without intermediate conversion steps
Q.77 Which of the following best describes 'hydrogen fuel cell electric vehicles (FCEVs)'?
Vehicles that store electricity in large capacitors
Vehicles that use hydrogen to generate electricity on board via a fuel cell
Vehicles that run on gasoline with a small hydrogen injector
Vehicles that use hydrogen only for heating the cabin
Explanation - FCEVs contain a fuel‑cell stack that converts stored hydrogen into electricity to drive an electric motor.
Correct answer is: Vehicles that use hydrogen to generate electricity on board via a fuel cell
Q.78 Which factor most directly influences the rate of hydrogen diffusion through a PEM?
Membrane thickness
Catalyst particle size
Operating pressure
Ambient humidity
Explanation - Thinner membranes reduce diffusion path length, enhancing proton transport and overall cell performance.
Correct answer is: Membrane thickness
Q.79 In a fuel cell, the term "stack voltage" is typically:
The sum of the open‑circuit voltages of each cell in the stack
The voltage of a single cell under load
The voltage measured across the hydrogen tank
The voltage required to start the cell
Explanation - Stack voltage is the additive voltage of all cells connected in series, providing higher total voltage.
Correct answer is: The sum of the open‑circuit voltages of each cell in the stack
Q.80 Which of the following is a major obstacle to large‑scale adoption of green hydrogen?
Abundant cheap renewable electricity
High efficiency of electrolysis
High capital cost of electrolyzers and storage infrastructure
Lack of hydrogen demand
Explanation - Current electrolyzer technology and storage solutions are expensive, limiting widespread green hydrogen deployment.
Correct answer is: High capital cost of electrolyzers and storage infrastructure
Q.81 The term "fuel cell degradation rate" is usually expressed as:
Volts per hour
Percentage loss of power per 1000 operating hours
Kilograms of hydrogen per day
Liters of water produced per minute
Explanation - Degradation is typically reported as % loss of initial performance over a defined number of hours.
Correct answer is: Percentage loss of power per 1000 operating hours
Q.82 Which of the following materials is commonly used for the bipolar plates in PEM fuel cells to reduce cost?
Pure gold
Stainless steel coated with conductive graphite
Copper with silver plating
Aluminum alloy without coating
Explanation - Graphite‑coated stainless steel offers good conductivity and corrosion resistance at lower cost than pure graphite.
Correct answer is: Stainless steel coated with conductive graphite
Q.83 In the context of fuel cells, the term "partial pressure" is important because:
It determines the mechanical strength of the cell
It directly influences the Nernst potential and reaction rates
It controls the temperature of the stack
It sets the speed of the coolant flow
Explanation - The Nernst equation incorporates reactant partial pressures, affecting cell voltage.
Correct answer is: It directly influences the Nernst potential and reaction rates
Q.84 Which fuel cell type can operate directly on ammonia (NH₃) after internal cracking?
Alkaline Fuel Cell (AFC)
Solid Oxide Fuel Cell (SOFC)
Proton Exchange Membrane Fuel Cell (PEMFC)
Phosphoric Acid Fuel Cell (PAFC)
Explanation - SOFCs can thermally decompose ammonia into H₂ and N₂, then use the H₂ in the cell.
Correct answer is: Solid Oxide Fuel Cell (SOFC)
Q.85 What is the main environmental advantage of using fuel cells in maritime transport compared to conventional diesel engines?
Higher speed capability
Zero sulfur oxides (SOₓ) and particulate emissions
Lower construction costs
Simpler navigation systems
Explanation - Hydrogen fuel cells emit only water, eliminating SOₓ, NOₓ, and particulate matter typical of diesel engines.
Correct answer is: Zero sulfur oxides (SOₓ) and particulate emissions
Q.86 Which of the following best explains why PEM fuel cells require humidification of the inlet gases?
To cool the cell
To maintain membrane conductivity by keeping it hydrated
To increase the pressure inside the cell
To remove impurities from the gases
Explanation - The polymer membrane conducts protons only when adequately hydrated; dry gases cause dehydration and increased resistance.
Correct answer is: To maintain membrane conductivity by keeping it hydrated
Q.87 Which of the following processes can be used to produce 'green' hydrogen?
Steam methane reforming without carbon capture
Electrolysis powered by renewable electricity
Partial oxidation of coal
Thermal cracking of natural gas
Explanation - When the electricity comes from wind, solar, or hydro, the hydrogen produced is considered green because no CO₂ is emitted.
Correct answer is: Electrolysis powered by renewable electricity
Q.88 The term 'hydrogen fuel cell stack voltage degradation' over time is mainly caused by:
Loss of hydrogen storage capacity
Increase in membrane resistance and catalyst poisoning
Decrease in ambient temperature
Growth of the fuel cell size
Explanation - Aging of the membrane and catalyst reduces conductivity and activity, lowering the stack voltage.
Correct answer is: Increase in membrane resistance and catalyst poisoning
Q.89 Which of the following is NOT a typical component of a hydrogen refueling station?
Hydrogen compressor
High‑pressure storage tanks
Electrolyzer for on‑site hydrogen generation
Coal‑fired boiler
Explanation - Coal‑fired boilers are unrelated to hydrogen refueling; stations use compressors, storage, and sometimes electrolyzers.
Correct answer is: Coal‑fired boiler
Q.90 What is the main reason that PEM fuel cells have a relatively low operating temperature compared with SOFCs?
The catalyst used in PEMFCs melts above 100 °C
The polymer electrolyte degrades at higher temperatures
Hydrogen cannot be supplied at high temperature
Water management is easier at low temperature
Explanation - Nafion and similar polymers lose mechanical stability and conductivity above about 120 °C, limiting PEMFC operating temperature.
Correct answer is: The polymer electrolyte degrades at higher temperatures
Q.91 Which of the following statements about hydrogen fuel cell efficiency is correct?
Fuel cell efficiency is independent of load
Fuel cells can achieve > 80 % electrical efficiency under optimal conditions
Fuel cells always have lower efficiency than internal combustion engines
Fuel cells produce more CO₂ than gasoline engines
Explanation - Ideal PEMFCs can reach up to ~80 % electrical efficiency; practical systems achieve 50‑60 % due to losses.
Correct answer is: Fuel cells can achieve > 80 % electrical efficiency under optimal conditions
Q.92 In fuel cell terminology, the term 'polarization curve' is used to illustrate:
The relationship between voltage and current density
The change in temperature over time
The variation of pressure with flow rate
The spectrum of emitted light
Explanation - A polarization curve plots cell voltage versus current density, revealing activation, ohmic, and concentration losses.
Correct answer is: The relationship between voltage and current density
Q.93 Which type of fuel cell is most suited for portable military power due to its rapid start‑up and low thermal signature?
Molten Carbonate Fuel Cell (MCFC)
Solid Oxide Fuel Cell (SOFC)
Proton Exchange Membrane Fuel Cell (PEMFC)
Alkaline Fuel Cell (AFC)
Explanation - PEMFCs start quickly, operate at low temperature, and have low infrared signatures, making them ideal for portable applications.
Correct answer is: Proton Exchange Membrane Fuel Cell (PEMFC)
Q.94 The term 'hydrogen isotopes' refers to:
Hydrogen, deuterium, and tritium
Hydrogen, oxygen, and nitrogen
Protons, neutrons, and electrons
Hydrogen, helium, and lithium
Explanation - Isotopes of hydrogen differ in neutron count: protium (¹H), deuterium (²H), tritium (³H).
Correct answer is: Hydrogen, deuterium, and tritium
Q.95 Which of the following best explains why fuel cells produce less noise than combustion engines?
Fuel cells operate in a vacuum
Fuel cells have no moving mechanical parts producing vibrations
Hydrogen combustion is silent
Fuel cells use sound‑absorbing materials
Explanation - Electrochemical conversion generates electricity without pistons, valves, or exhaust, resulting in very low acoustic noise.
Correct answer is: Fuel cells have no moving mechanical parts producing vibrations
Q.96 Which of the following is a major challenge for the widespread deployment of hydrogen pipelines?
Hydrogen's high viscosity
Hydrogen's tendency to cause embrittlement in steel pipelines
Hydrogen's inability to dissolve in water
Hydrogen's high density compared with natural gas
Explanation - Hydrogen can diffuse into steel, reducing ductility and leading to cracks; special alloys or coatings are required.
Correct answer is: Hydrogen's tendency to cause embrittlement in steel pipelines
Q.97 Which fuel cell type is characterized by the use of a solid ceramic electrolyte that conducts oxygen ions?
Alkaline Fuel Cell (AFC)
Solid Oxide Fuel Cell (SOFC)
Proton Exchange Membrane Fuel Cell (PEMFC)
Molten Carbonate Fuel Cell (MCFC)
Explanation - SOFCs employ a dense ceramic (e.g., YSZ) that conducts O²⁻ ions at high temperature.
Correct answer is: Solid Oxide Fuel Cell (SOFC)
Q.98 In a PEM fuel cell, the anode catalyst typically facilitates which reaction?
Oxygen reduction to water
Hydrogen oxidation to protons and electrons
Water splitting into hydrogen and oxygen
Carbon dioxide reduction
Explanation - At the anode, H₂ is split into H⁺ and e⁻; the catalyst (usually Pt) speeds up this reaction.
Correct answer is: Hydrogen oxidation to protons and electrons
Q.99 Which of the following is a primary reason for using a fuel cell in a spacecraft power system?
High thrust generation
Zero gravity operation
High specific energy and low vibration
Ability to use lunar dust as fuel
Explanation - Fuel cells provide high energy density and silent operation, crucial for spacecraft where mass and vibration are critical.
Correct answer is: High specific energy and low vibration
Q.100 The term 'hydrogen fuel cell vehicle (FCV)' is synonymous with:
Battery electric vehicle (BEV)
Hybrid electric vehicle (HEV)
Fuel cell electric vehicle (FCEV)
Plug‑in hybrid vehicle (PHEV)
Explanation - FCV and FCEV both refer to vehicles that generate electricity onboard via a hydrogen fuel cell.
Correct answer is: Fuel cell electric vehicle (FCEV)
Q.101 Which method is used to increase the durability of PEM fuel cell membranes under high‑temperature operation?
Adding silica fillers to the polymer matrix
Increasing membrane thickness to 5 mm
Operating at sub‑zero temperatures
Using liquid electrolytes instead
Explanation - Nanofillers improve thermal stability and mechanical strength, allowing operation at slightly higher temperatures.
Correct answer is: Adding silica fillers to the polymer matrix
Q.102 What is the primary chemical form of hydrogen stored in compressed gas cylinders?
Atomic hydrogen
Molecular hydrogen (H₂)
Ionic hydrogen (H⁺)
Hydrogen sulfide (H₂S)
Explanation - Compressed cylinders contain H₂ molecules at high pressure (e.g., 350–700 bar).
Correct answer is: Molecular hydrogen (H₂)
Q.103 Which of the following is a direct environmental benefit of using renewable‑based green hydrogen in industry?
Increased CO₂ emissions
Reduced reliance on water resources
Elimination of fossil‑fuel‑derived CO₂ emissions
Higher nitrogen oxide (NOₓ) production
Explanation - Green hydrogen production emits no CO₂, helping decarbonize sectors like steelmaking and ammonia synthesis.
Correct answer is: Elimination of fossil‑fuel‑derived CO₂ emissions
Q.104 The term "fuel cell stack" is best described as:
A single fuel cell with a membrane
Multiple fuel cells connected in series to increase voltage
A storage tank for hydrogen
An electronic controller for the fuel cell
Explanation - Stacks combine many cells to achieve the desired voltage and power output.
Correct answer is: Multiple fuel cells connected in series to increase voltage
Q.105 Which factor is most critical for preventing catalyst poisoning in PEM fuel cells?
Maintaining high temperature
Ensuring low carbon monoxide (CO) concentration in the hydrogen feed
Increasing the pressure of the oxidant
Using a thicker membrane
Explanation - CO binds strongly to Pt sites, reducing catalytic activity; PEMFCs require <10 ppm CO.
Correct answer is: Ensuring low carbon monoxide (CO) concentration in the hydrogen feed
Q.106 Which of the following is a common method for recycling spent fuel cell catalysts?
Incineration
Acid leaching to recover precious metals
Melting and recasting into new catalysts
Biodegradation
Explanation - Acid leaching dissolves platinum-group metals for recovery and reuse, reducing waste and cost.
Correct answer is: Acid leaching to recover precious metals
Q.107 Which type of fuel cell can directly use liquid methanol as fuel without external reforming?
Alkaline Fuel Cell (AFC)
Direct Methanol Fuel Cell (DMFC)
Proton Exchange Membrane Fuel Cell (PEMFC)
Solid Oxide Fuel Cell (SOFC)
Explanation - DMFCs oxidize methanol at the anode, producing CO₂, water, and electricity without a separate reformer.
Correct answer is: Direct Methanol Fuel Cell (DMFC)
Q.108 The primary reason for using a fuel cell's waste heat in combined heat and power (CHP) systems is:
To increase the cell's voltage
To improve overall system efficiency by utilizing otherwise lost thermal energy
To cool the fuel cell faster
To generate hydrogen again
Explanation - CHP captures waste heat for heating or additional electricity generation, raising total energy utilization.
Correct answer is: To improve overall system efficiency by utilizing otherwise lost thermal energy
Q.109 Which of the following statements about 'hydrogen fuel cell electric buses' is correct?
They store electricity in large batteries only
They use a fuel cell to generate electricity on board from stored hydrogen
They require diesel fuel for start‑up
They cannot be refueled quickly
Explanation - Hydrogen buses carry a fuel‑cell stack and hydrogen tanks; the stack produces electricity for the motor.
Correct answer is: They use a fuel cell to generate electricity on board from stored hydrogen
Q.110 Which of the following is a common method for on‑site generation of hydrogen at a refueling station?
Steam methane reforming with carbon capture
Electrolysis using grid electricity
Hydrogen extraction from seawater
Photovoltaic hydrogen synthesis
Explanation - SMR with CCS is currently the most economical way to produce large quantities of hydrogen on site.
Correct answer is: Steam methane reforming with carbon capture
Q.111 In fuel cell terminology, 'activation loss' is primarily caused by:
Resistance of the electrolyte
Kinetic barriers of the electrode reactions
Fuel crossover through the membrane
Heat loss to the environment
Explanation - Activation loss reflects the energy required to overcome reaction kinetics at low current densities.
Correct answer is: Kinetic barriers of the electrode reactions
Q.112 Which of the following statements accurately describes the 'hydrogen economy'?
Hydrogen replaces all electricity generation worldwide
Hydrogen is produced, stored, and used as a clean energy carrier across multiple sectors
Hydrogen is only used in rocket propulsion
Hydrogen can only be stored as liquid at cryogenic temperatures
Explanation - The hydrogen economy envisions hydrogen as a versatile, low‑carbon energy carrier for transport, industry, and power.
Correct answer is: Hydrogen is produced, stored, and used as a clean energy carrier across multiple sectors