The measured operating cell potentials at -10.0 mA cm -2 were -1.55 V for the sHER|BPM|GEOR cell and -2.45 V for the sHER|BPM|OER cell (Figure ). The excess potential again is likely related to membrane and solution resistance unaccounted for in the load -line analysis, in addition to the slow oxidation of the anode surface in the case of the GEOR reaction. The cell potential increased by less than 0.1 V in the 20 h period of each experiment. The advantage of using the GEOR anode is evident in the steady 0.9 V reduction in overall cell potential.