Unveiling the Potential of Ag₂S Reference Electrode: Empowering Calcium Electrochemical Reactions

With the escalating global energy demands, the quest for postlithium technologies, such as calcium batteries, has gained significant momentum. Nevertheless, a formidable hurdle in calcium research resides in the scarcity of suitable reference electrodes. This study introduces a silver(I) sulfide (Ag₂S) reference electrode for use in calcium-ion battery research based on a silver wire coated with silver(I) sulfide crystals. Comprehensive structural characterization through Raman spectroscopy, coupled with a 48 h cyclic voltammetry electrochemical analysis, has been conducted. By utilizing three nonaqueous calcium-ion electrolytes, the standard reduction potential of Ag2S relative to the standard hydrogen electrode has been determined, along with the quantification of voltage drift over time. The Ag₂S standard reduction potentials varied from −0.291 to −0.477 V vs SHE, and the drift followed a linear behavior with slopes between −0.28 and −2.45 mV/h. A side reaction between ferrocene and silver ions is also observed with voltages scanned above 0.65 V. Ag₂S shows promise as a reference electrode material for future calcium-ion battery research.