Describe the composition of the electrodes in a hydrogen-oxygen fuel cell.

State the half-equation at each electrode in the hydrogen-oxygen alkaline cell.

Positive electrode (cathode):

Negative electrode (anode):

(porous) carbon/graphite electrodes (impregnated) with Pd/Pt/Ag catalysts;

Just Pb/Pt/Ag not sufficient for mark.

Positive electrode (cathode):

${{\text{O}}_2}{\text{(g)}} + {\text{2}}{{\text{H}}_2}{\text{O(l)}} + {\text{4}}{{\text{e}}^ - } \to {\text{4O}}{{\text{H}}^ - }{\text{(aq)}}$;

Negative electrode (anode):

${{\text{H}}_2}{\text{(g)}} + {\text{2O}}{{\text{H}}^ - }{\text{(aq)}} \to {\text{2}}{{\text{H}}_2}{\text{O(l)}} + {\text{2}}{{\text{e}}^ - }$;

Ignore state symbols.

Allow e instead of ${e^ - }$.

Award [1] if equations are correct but electrodes reversed.

The question on fuel cells was poorly answered, with very few including both graphite and a Pd or Pt or Ag metal in the composition of electrodes.

Only the better candidates had no difficulty with the half-equations at each electrode in the hydrogen-oxygen alkaline fuel cell.