Using the example of theHydrogen fuel cell hydrogen fuel cellFuel cell in acid electrolyte, electronic structuresElectronic structure are used to take into account the electrochemical potential of electrons on the cathode, anode, and the connecting wire. In the absence of ion flow in the electrolyte, the anode and cathode reactions with H2 and O2 are at equilibrium with the respective oxidation and reduction products. At a catalytic anode the electron chemical potentialElectron chemical potential for the H2 oxidation equilibrium establishes the thermodynamic work function and potential of the electrode surface. Similarly, at a catalytic cathode the electron chemical potential for the O2 reduction equilibrium determines the potential of the electrode surface. Band bending is invoked to connect the surface and bulk electronic structures. When ion conduction in the electrolyte is turned on, electrons generated at the metal cathode enter the conduction bandConduction band and protons enter the electrolyte. These combine with O2 at the cathode where the electron is 1.2 eV more stable. Along the way the electron loses this energy by generating heat, light or electromagnetic energy. PolarizationsPolarization at interfaces represented by band bending do not affect the electron energy relative to the cathode as it moves in the wire via the conduction bandConduction band.