Altklausurfragen

two gas diffusion layers that shall enhance permeation to the membrane (false)

two gas diffusion layers that shall make permeation to the membrane more difficult (falsch)

the mass of polymer electrolyte providing 1 mole of exchangeable protons (richtig)

the mass of one square meter of electrolyte (falsch)

Y2O3

Yb2O3

nicht:

Gd2O3

CaO

nicht

H2S

Mercaptane

nicht:

Thiophene

Mass of water=Volume×Density = 5000g

Number of moles of water=Molar mass/Mass of water​= 5000g/18g/mol=277,78mol

For every mole of water produced, 2 moles of electrons are transferred.

Moles of electrons=277.78 mol×2 mol e−/mol =555.56mol e−

Total charge=Moles of electrons×F

t=I/Total charge​=372h

Mercaptane, H2S

nicht: Triophone

A solid Oxide Fuel Cell

nicht: An Alkine Fuel Cell

False: Low temperature URFC are based on solid oxide cells

True: Circulation of a dry inert gas can be utilized to dry the compartments after switching from electrolysis to fuel cell mode

The stability of metals to which a voltage is applied depending on PH

not:

The kinetic effect on metals to which a voltage is applied depending on pH

The conductivity of catalysts

The resistance of fuel cells

The water molecule gets broken at the anode

The electrodes of a PEM electrolysis need precious metals

not: THe hydrogen usually gets dried after compression

If steam instead of liquid water is provided in electrolysis the polarization curve will never start above the thermo-neutral voltage

If the enthalpy of evaporation is covered by heat input the necessary voltage to get an electgrolysisi process going starts at the thermoneutral voltage

Due to their higher anode potentials compared to fuel cells corrosion of the anode catalyst is a more severe pronlem

At present good eletrolysers can achieve about 70% of efficiency based on lower heating value, which corresponds to an operating voltage of 1.8V

Some minor CO2 evolution occurs at the cathode as well

Water Transport throught the anode layer toward the electrolyte

Diffusion of methanol from the anode toward the cathode

not:

Proton transport through the electrolyte from the cathode toward the anode

False: Ethanol procides higher power densities in direct fuel cells compared to methanol owing to its C-C binding

True:

Direct fuel cells need much less balance of plant components compared to other low temperature fuel cells using carbonaceous fuels as no fuel reforming is necessary

all true:

The polymer Nafion forms a crystalline and amorphous regions in the so called bock bone

The crystaline regions disintegrate at the glass transition temperature allowing for hot pressing for improving the electrode- electrolyte interface

inkjet printing is a viable technology for electrode deposition

Nafion membranes exhibit notable swelling in the percent range of their dimensions when they take up water

True:

The elctrolyte of PAFCs is H3PO4

The lifetime of a PAFC cells is limited by evaporation of the phosphoric acid

To prevent electrolyte crystallization below 42.5°C the stack is either kept at temperature or wettet through air supply

false:

Fuel starving at the cathode can be tolerated

true:

adsorption of mercaptane via active carbon

chemical reaction of mercaptane in a zink oxide reactive bed

not:

Hydrogenation of mercaptane

True:

On the distribution grid level odorants like mercaptane and thiophene are added as odorants to natural gas

Above a certain amount of sulfur containing components in the gas stream the fuel cell degrades

false:

Sulfur degradtion is generally reversible by providing a pure H2 gas stream to the fuel cell for a certain amount of time

True:

Methannation of CO can be used for fine clean up of reformed gas for for PEM Fuel cells

An advantage pf autothermal reforming of carbonaceaous energy sources is that there is no need for an additional heat exchanger

In a palladium-silver membrane reactor the hydrogen permeates through the solid PdAg membrane material

False:

Le Chatelier’s priciple postulates that for a endothermic reaction the reaction equilibrium is shifted to the reaction products if the tremerature is decreased

True: Produces more hydrogen at higher temperatures because the equilibrium is beneficial for hydrogen production at higher temperatures

is described by: CO +H2O —> <— Co2+H2

Is part of balancing the thermal effects in autothermal reforming

false: Is an endothermic reaction

True:

At the neutral point of pH=7 there are as many hydroxyl ions as hydronium ions

Owing to a movement of hydronium ions with thier hydration shels along the chemical gradient wateris dragged from the anode to the cathode in a PEM fuel cell

false:

The interaction of ions at higher concentrations leads to higher conductivity

True: Equally charged ions can have different conductivity in water

false:

The ionic radius of a cation determines its conductivity in water

In a infinite dilution a pH of 7 leads to the highes conductivity

The Grotthus mechanism represents the dominantn transformation mechanism in alkaline fuel cells

true: The activation energy cannot be used to generate electricity

The current in the activation potential regime is described by the Butler volmer Equation