Electrochemical power

Chemical (Gibbs) energy to electrical energy

  • Fuel cells

    • Fuels: H\(_2\), Reformed CH\(_3\)OH, Reformed CH\(_4\)
    • Electrolytes: Alkaline, Acid(Phosphoric acid and PEM), Molten carbonate, Solid oxide(Y-doped Zr), Proton ceramic(oxides with dissolved water)

  • Batteries:

    • Primary (one time use)
      • Dry cell
        • NH\(_4\)Cl + ZnCl\(_2\) paste
        • C in powder composite cathode
      • Alkaline battery (most used today)
        • Negative: \(\mathrm{Zn}(s)+2 \mathrm{OH}^{-}(a q) \rightarrow 2 \mathrm{e}^{-}+\mathrm{ZnO}(s)+\mathrm{H}_{2} \mathrm{O}(\ell)\)
        • Positive: \(\mathrm{MnO}_{2}(s)+\mathrm{H}_{2} \mathrm{O}(\ell)+\mathrm{e}^{-} \rightarrow \mathrm{MnOOH}(s)+\mathrm{OH}^{-}(a q)\)
        • Other alkaline positrodes:
        • \(\left\{\begin{array}{l}\mathrm{HgO}(s)+\mathrm{H}_{2} \mathrm{O}(\ell)+2 \mathrm{e}^{-} \rightarrow \mathrm{Hg}(\ell)+2 \mathrm{OH}^{-}(a q) \\ \mathrm{Ag}_{2} \mathrm{O}(s)+\mathrm{H}_{2} \mathrm{O}(\ell)+2 \mathrm{e}^{-} \rightarrow 2 \mathrm{Ag}(s)+2 \mathrm{OH}^{-}(a q) \\ \frac{1}{2} \mathrm{O}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(\ell)+2 \mathrm{e}^{-} \rightarrow 2 \mathrm{OH}^{-}(a q)\end{array}\right.\)
    • Secondary (rechargeable)
      • Lead acid:
        • Corrosion of the positive (Pb(s)) electrode
        • Oxygen evolution from the positive electrode (H2O -> H3O)
        • Hydrogen evolution at the negative electrode (H3O-> H2O)
        • Oxygen reduction at the negative electrode (O + H3O -> H2O)

  • Redox flow battery

  • Positive: \(\mathrm{VO}_{2}^{+}(a q)+2 \mathrm{H}_{3} \mathrm{O}^{+}(a q)+\mathrm{e}^{-} \underset{\text { recharge }}{\stackrel{\text { discharge }}{\leftrightarrows}} \mathrm{VO}^{2+}(a q)+3 \mathrm{H}_{2} \mathrm{O}(\ell)\)

  • Negative: \(\mathrm{V}^{2+}(a q) \underset{\text { recharge }}{\stackrel{\text { discharge }}{\rightleftarrows}} \mathrm{e}^{-}+\mathrm{V}^{3+}(a q)\)

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