In a hydrogen-oxygen fuel cell, the anode is made of porous carbon with catalyst Pd or Pt and the cathode is also made of porous carbon containing the catalyst Pt. Between then is an electrolyte made of aqueous hydroxide (KOH or NaOH). Hydrogen gas is oxidized by oxygen gas in a controlled manner. Electrons are drawn from the anode to the cathode producing direct current electricity. Individual fuel cells produce a relatively small electrical potential of 0.7 Volts (theoretically 1.23 V), so cells are placed in series to increase voltage and meet an application’s requirement.
Balanced equation: 2 H2 + O2 → 2 H2O
There are many advantages of hydrogen fuel cells. In addition to electricity, fuel cells also produce water, heat and very small amount of other emissions. The energy efficiency of a fuel cell is about 40 – 60 %, or can be up to 85% if waste heat is captured in cogeneration situation such as combine heat and power for residential use. Low temperature fuel cells have low heat transmission which makes them ideal for military application. A high power density allows fuel cells to be relatively compact source of electric power, beneficial in application with space