where ❁ ❂❃❄❅❆ is the net enthalpy change due to the electrochemical reactions, ❇❉❊ ❋❉●❈❉❊ ❋❉● ❍ ❍ is the product of the transfer current and the overpotential in the anode or the cathode TPB, ■❏❑▲ is the Rohmic resistivity of the conducting media, and ▼◆ is the enthalpy change due to condensation/vaporization of water.