The standard potential of the reaction: H2O+e−→12H2+OH− at 298 K by using Kw(H2O)=10−14.
We know
ΔG=−RTlnK
∵ΔG=−nFE
∴−nFE=−RTlnK
∴−1×96500×E=−8.314×298ln(10−14)
∴E=−0.828 V
Standard electrode potential of NHE at 298 K is