Chlor-alkali electrolysis continues to pose challenges for researchers. Replacement of the hydrogen-evolution reaction by the oxygen-reduction reaction can reduce the overpotential of the cathodic process, depolarizing the overall reaction and saving energy. Here, we describe a series of experiments to determine the cell voltage and energy savings when a copper-doped carbon/polytetrafluoroethylene (PTFE) oxygen-diffusion cathode is used in brine electrolysis experiments, instead of a hydrogen-evolving graphite cathode. Voltammetric studies were carried out to determine the ideal oxygen flow rate through the porous cathode structure and the amount of copper that maximizes oxygen-reduction current densities. Brine electrolysis was performed in a two-compartment membrane cell using a TiO2/RuO2 anode. Our findings indicate a strong depolarizing effect with the copper-doped oxygen-diffusion cathode. Comparison of the results using a graphite (hydrogen-evolving) cathode and a copper-doped cathode at 70 degrees C showed that the latter resulted in 42% reduction in energy demand.