Construction and Evaluation of Cheap and Robust Miniature Ag/AgCl Reference Electrodes for Aqueous and Organic Electrolytes

Stable reference electrodes (REs) are crucial for reliable voltammetry, controlled potential electrosynthesis, or spectro-electrochemistry. Yet, inferior pseudo-REs, such as plain Ag wire are often used, because commercial REs are expensive, may degrade or contaminate under required conditions, or don't fit geometric restrictions of custom setups. Addressing such cases, we report construction, benchmarking and utilization of easy to make, cheap (<1), and robust miniature REs from pasteur pipettes, molecular sieve beads and Ag wire. Excellent potential precision and accuracy with at least 1 week device stability was obtained for aqueous Ag/AgCl REs with 3 M NaCl in H2O and anhydrous 0.1 M TBACl in MeCN inner-electrolytes. Even in alkaline 1 M NaOH electrolyte, where initial Ag/AgCl REs quickly convert to Ag/Ag2O (1 M NaOH) REs, perfect potential precision, accuracy, and at least 1 week stability are demonstrated. According to experimental needs, miniature REs can be built with many organic and aqueous electrolytes. For these custom use-cases, we report guidelines to calibrate absolute RE potential, and to assess device precision, accuracy and stability. Finally, electro-hydrogenation of styrene on nickel electrodes exemplifies superiority of Ag/AgCl REs over Ag wire pseudo-REs, affording more reliable electrolysis current, cell potential and potential dependent Faraday efficiency.