Judicious selection, validation, and use of reference electrodes for in situ and operando electrocatalysis studies

The development and implementation of in situ and operando characterization techniques to understand electrocatalytic processes, establish structure-property-performance relationships, and elucidate properties of electrified interfaces aid in accelerating the discovery and design of new materials for sustainable energy technologies. The validity of operando characterization techniques is predicated on the ability to accurately and reliably control the electrochemical potential of the working electrode—factors dictated by the reference electrode. Because the utilization of an appropriate reference electrode is a prerequisite for reliable operando experiments, guidelines for the judicious selection, validation, and use of reference electrodes are necessary. In this review, we discuss existing knowledge and highlight examples of the use of reference electrodes (including quasi-reference electrodes), provide practical tips, and highlight challenges in the context of operando experiments in aqueous electrolytes. We discuss critical concepts (calibration, potential drift, and preparation) and prospective opportunities regarding the use of reference electrodes for operando characterization of electrocatalytic processes.