Solid-state Cd/Cd2+ reference electrode based on PMMA gel electrolytes

All solid-state reference electrode based on Cd/Cd2+ system was developed for the electrochemical measurements in aprotic organic carbonates (propylene PC, ethylene EC and dimethyl carbonate DMC). The electrode was designed by using poly(methyl methacrylate) - propylene carbonate polymer electrolyte with immobilised Cd(ClO4)2 solution and a cadmium wire. The electrode performance in various solvents was studied including potential determination and its dependence on the solution ionic strength. Cyclic voltammetry of ferrocene in particular solvents showed good reproducibility of the electrode potential within the set of 18 electrodes: E(PMMA-Cd-Cd2+) = − 0.439 ± 0.013 vs. SCE in propylene carbonate. Also long-term chronopotentiometric measurements showed good potential stability and no potential drift within 3-week continuous experiment. Three versions of electrode material filling were studied (glass frit, ceramic separator and graphite rod) with the aim to reduce unwelcome penetration of chemicals into the electrode material and leakage of cadmium ions into solution. Reliable electrochemical data were obtained during the 5-year employment of the PMMA-Cd-Cd2+ electrode.