Google for the fuel cell handbook from the DOE. Last I looked it was a clear intro. Wrt charge balances and driving force you need to remember this is a 3 phase system- h2 splits, ions migrate, charge balances by electron flow. Product is steam that wafts away so it is reasonable to think of a fuel cell as a battery with replenishable fuel. It's been a long time. I walked away from fuel cells in '02 or so. Nothing has changed and battery tech has completely owned any large scale opportunity