Comparison of Pt and IrO2-Ta2O5/Ti as a counter electrode in acidic media

Abstract

Platinum has been widely employed as a counter electrode (CE) for various electrochemical measurements; however, the potential dissolution of Pt from the CE during electrochemical processes may skew the results of electrochemical studies, particularly for cathodic reactions (e.g., hydrogen evolution, oxygen reduction, and CO2 reduction). For this study, we compared the electrochemical behaviors of Pt and IrO2-Ta2O5/Ti electrodes as CEs in 0.5 M H2SO4. To study the effects of various surface areas, a smooth glassy carbon electrode with a small geometric surface area (GSA) of 0.07 cm2 (GCE-s), a smooth medium GCE with a GSA of 0.38 cm2 (GCE-m), and carbon cloth (CC) with a large GSA of 2.00 cm2 were employed as working electrodes (WEs). When Pt was used as the CE, the current of the GCE-s was slowly enhanced after 1000 cycles, while a notable current increase at the GCE-m was seen after 800 cycles. For the CC electrode, a prominent increase in the current was observed after 400 cycles. The increased HER activity was initiated through the deposition of Pt dissolved from the CE during cyclic voltammetric cycles in the potential range between −0.40 and 0.0 V vs. Ag/AgCl. In contrast, no notable current increase was observed for any of the GCE-s, GCE-m, and CC electrodes during 2000 cycles when the IrO2-Ta2O5/Ti electrode was employed as the CE.

Keywords

• Counter electrode
• Platinum dissolution
• Dimensionally stable anode
• Electrocatalysis
• Hydrogen evolution