2H++2e−→H22 \mathrm{H}^{+}+2 \mathrm{e}^- \rightarrow \mathrm{H}_{2}2H++2e−→H2
Cu→Cu2++2e−\mathrm{Cu} \rightarrow \mathrm{Cu}^{{2+}}+2 \mathrm{e}^-Cu→Cu2++2e−
H2→2H++2e−\mathrm{H}_{2} \rightarrow 2 \mathrm{H}^{+}+2 \mathrm{e}^-H2→2H++2e−
Cu2++2e−→Cu\mathrm{Cu}^{2+}+2 \mathrm{e}^- \rightarrow \mathrm{Cu}Cu2++2e−→Cu
