Selecting the Reference Electrode

REs are required in PEC testing in order to measure the potential of the WE on a well-defined electrochemical scale, typically versus the normal hydrogen electrode (NHE). Several REs are available, but saturated calomel electrodes (SCE, SCE +0.241 V vs. NHE at 25 °C) and silver-silver chloride in saturated KCl (Ag/AgCl, EAg/AgCi sat d KCl = +0-197 V vs. NHE at 25 °C) electrodes are easiest to use and usually preferred for tests in acidic solutions for the sake of convenience [21]. Note that Ag/AgCl reference electrodes with saturated KCl are not compatible with perchloric acid (HCIO4) electrolytes since KCIO4 will precipitate in the frit. Replacement with NaCl solution may be a suitable solution. 

The SCE and Ag/AgCl reference electrodes can generally be used in a wide range of pH values. However, immersion for a long period of time in basic solutions could damage the electrode frit. Thus, Hg/HgO reference electrodes 

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In lithium batteries, one usually selects the reference electrode to be lithium metal, and a 1 1 binary electrolyte is generally used. Then So = s = 0, =... 

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