Real-Time Carbon Monoxide Detection using a Rotating Gold Ring Electrode: A Feasibility Study

Rotating ring-disc electrodes (RRDEs) offer a powerful electroanalytical method for studying electrochemical reactions with continuous real-time feedback capabilities. However, its use in the electrochemical CO2 reduction reaction (CO2RR) sees very limited success despite the method being a sensible choice. Here, we assess the use of commercial polycrystalline Pt and Au ring electrodes for the selective detection of CO in a near-neutral NaHCO3 electrolyte (pH=7.5) and their suitability for real-time monitoring during the CO2RR. Our results show that the commercial Pt ring electrode, as a highly sensitive detector, cannot discriminate among most of C1 reduction products such as H2, CO, formate, formaldehyde and methanol, whereas the Au ring electrode can satisfy many criteria for real-time CO detection but the poor sensitivity of the polycrystalline electrode prohibits the practical use for quantitative purpose. A set of design principles for the Au-based ring electrode is put forward in order to endow RRDEs the capability of rapid real-time detection of CO in CO2 electroreduction.