Abstract
This work develops a new reference electrode for the electrochemical system using an aqueous supercritical carbon dioxide (sc-CO 2 ) emulsion solutions. Here, the Watts nickel bath is employed to be the standard testing electrolyte. A porous Pd-coated Ti (denoted as Pd/Ti) electrode is prepared by electroplating, which is subjected to the hydrogen sorption (including adsorption and absorption) reaction in 0.5 M H 2 SO 4 for forming a palladium hydride-coated titanium (denoted as PdH x /Ti) electrode. The hydrogen sorption/desorption behavior on Pd/Ti is characterized by cyclic voltammetry and rest potential against time analyses. These results reveal that PdH x /Ti is a reliable reference electrode with a reproducible and stable PdH x potential (longer than 10 h) in normal aqueous electrolytes at room temperature. The equilibrium potential of this PdH x /Ti electrode is about 65 ± 15 mV (vs.RHE) in the Watts Ni bath. Although the hydrogen desorption rate is enhanced by elevating the solution temperature, all of the results confirm that the in-situ formed PdH x /Ti electrode can be practically utilized as a reference electrode in the Watts Ni bath containing the sc-CO 2 emulsion medium.