Multiscale  Materials

Membranes can be of various thickness, with homogeneous or heterogeneous structure.

Membrane can also be classified according to their pore diameter. Membranes can be neutral or charged, and particles transport can be active or passive. The latter can be facilitated by pressure, concentration, chemical or electrical gradients of the membrane process. Membranes can be generally classified into synthetic membranes and biological membranes.

A proton exchange membrane or polymer electrolyte membrane (PEM) is a semipermeable membrane generally made
from ionomers and designed to conduct protons while being impermeable to gases such as oxygen or hydrogen.

The advantage of the alkali anion exchange membrane in the fuel cell is the potential to use non-noble metals such as iron, cobalt or nickel due to the low overpotentials associated with electrochemical reactions at high pH.

In comparison against alkaline fuel cell, alkali anion exchange membrane fuel cells also protect the electrode from solid carbonate precipitation, which can cause fuel (oxygen/hydrogen) transport problem during start-up.