Question

Each question can be more than one correct answers.

3) Gas diffusion layers for PEM fuel cells: a) must be hydrophobic in order to hydrate the electrolyte b) show a lower porosity than MPLS c) are electronic conductors d) are responsible for crossover losses 4) Piezopolymers: a) do not show ferroelectric properties b) are able to maintain dipoles alignment c) show a perovskite lattice d) do not exhibit saturation polarization

Answer 1

3)

a) INCORRECT. Layer bas to be hydrophilic

b) CORRECT. MPL would allow oxide ions to go through as well, PEM should not.

c) INCORRECT. Electrons are conducted through an external circuit.

d) CORRECT. There is some finite loss of protons during the crossing over across the membrane.

4)

a) CORRECT. They do not show ferroelectric properties.

b) INCORRECT. Dipoles are aligned only as long as external pressure is applied.

c) CORRECT. Piezoelectric materials do display pervoskite latticenstructures.

d) INCORRECT. Piezoelectric materials do show a saturation in polarization.