Investigating the failure mechanisms of screen-printed reference electrodes

Stable reference electrodes are essential for reliable electrochemical measurements, including in electroanalytical devices, and for continuous environmental monitoring in particular, yet many SPREs are optimised for short-term, disposable use and their stability over multi-day operation remains limited. In this work, we target continuous monitoring, on the timescale of hours to weeks, where a compact, low-cost reference capable of maintaining a stable potential over time without requiring recalibration is essential. This study builds on our previous work on SPREs with polydimethylsiloxane (PDMS) junctions by systematically investigating their degradation mechanisms and the factors controlling operational lifetime. SPREs were fabricated on polyethylene terephthalate (PET) substrates using a KCl/poly(vinyl acetate) (KCl/PVAc) electrolyte reservoir and a PDMS junction.

Electrochemical characterisation demonstrated that depletion of the internal KCl reservoir is the dominant failure mechanism, with reference potential drift exceeding 1 mV h−1 once the electrolyte is no longer able to maintain saturation. Incorporating a PDMS junction markedly reduced Cl− leaching, extending operational lifetimes from <0.2 days to over 18 days in 3 M KCl solution. Electrochemical impedance spectroscopy and SEM–EDS analyses indicated that, beyond electrolyte depletion, localised AgCl degradation also contributes to long-term instability.

By quantifying the relationship between electrolyte volume, chloride retention, and potential drift, this work establishes direct links between SPRE structure, composition, and performance. These insights support improved SPRE designs for continuous monitoring applications and highlight the importance of junction integrity, water-resistant polymer components, and reproducible fabrication.