Editing Direct methanol fuel cell (section)

=== Cross-over current ===
Methanol on the anodic side is usually in a weak solution (from 1M to 3M), because methanol in high concentrations has the tendency to diffuse through the membrane to the cathode, where its concentration is about zero because it is rapidly consumed by oxygen. Low concentrations help in reducing the cross-over, but also limit the maximum attainable current.

The practical realization is usually that a solution loop enters the anode, exits, is refilled with methanol, and returns to the anode again. Alternatively, fuel cells with optimized structures can be directly fed with high concentration methanol solutions or even pure methanol.<ref>{{cite journal|last=Li|first=Xianglin|author2=Faghri|title=Amir|journal=Journal of Power Sources|volume=226|pages=223–240|doi=10.1016/j.jpowsour.2012.10.061}}</ref>