Fuel cells produce voltage by using hydrogen and oxygen as raw materials, and releases water as a waste product.
Fuel cells can be alkaline or acidic, depending on the ion that moves across the electrolyte.
bAcidic fuel cells/b
mtaimg/images/topics/21/21-6-1.png/mtaimg
Half equations:
(2H+{(aq)} + 2e- ⇌ H{2 (g)} \qquad Eθ = 0.00 V )
(\frac{1}{2}O2 (g) + 2H^+{(aq)} + 2e- ⇌ H_2O{(l)} \qquad Eθ = +1.23 V )
Overall:
(H2 (g) + \frac{1}{2}O_{2 (g)} ⟶ H_2O_{(l)} \qquad E^θ_ = +1.23 V )
bAlkaline fuel cells/b
mtaimg/images/topics/21/21-6-2.png/mtaimg
Half equations:
(2H2O(l) + 2e^- ⇌ H_{2 (g)} + 2OH^-_{(aq)} \qquad E^θ = -0.83 V )
(\frac{1}{2}O2 (g) + H_2O_{(l)} + 2e^- ⇌ 2OH^-_{(aq)} \qquad E^θ = +0.40 V )
Overall:
(H2 (g) + \frac{1}{2}O_{2 (g)} ⟶ H_2O_{(l)} \qquad E^θ_ = +1.23 V )
bNon-hydrogen fuels/b
Methanol and other hydrogen-rich fuels can be used in fuel cells.