This Power-Point Shows The Basics Of A Hydrogen Dry Cell.
Also Here: hydrogen dry cell PP
Yea Here Is The New One:NEW AND IMPROVED VERSION
Some of the benefits of a dry cell are that it is much less corrosive than submersion. They are also very efficient, some 90% and up, unlike the average 20% of a combustion engine. They have much higher output than other generators too, small ones get up to 6 liters per minute, 3 huge party pop bottles in a minute.
The down sides are that they are extremely expensive, and ... I don't know what else but feel free to tell me.
More info here: DRY CELL PDF