Electrochemical and physicochemical degradability evaluation of printed flexible carbon electrodes in seawater

The environmental impact of metals and non-degradable plastics in printed electrodes has highlighted the need of employing sustainable materials in environmental monitoring. In this work, we developed a new sustainable graphite-based paste (G-PE) printed on a bioderived and biodegradable polyhydroxybutyrate polyhydroxyvalerate substrate for tap water and seawater monitoring. We compared its performance against two standard screen-printed electrodes (SPEs) fabricated using commercial silver and carbon pastes (Ag-SPEs and C-SPEs) printed on a polyvinyl chloride substrate. The Ag-SPEs exhibited the lowest sheet resistance (R_S = 0.053 Ω/sq), however they were also less reliable as silver oxidised and reacted with ions present in seawater. Meanwhile, the C-SPEs and G-PE presented similar R_S (26.9 and 30.1 Ω/sq, respectively), were inert in different media and showed relatively stable response during cyclic bending studies (less than 2.3% relative resistance variation for the C-SPE). Physical and chemical degradation studies of the sustainable G-PE in seawater demonstrated relatively quick ultrasound induced dissolution (less than5 min) while the SPEs did not dissolve even after 30 min of sonication, highlighting the suitability of this new, eco-friendly G-PE for single use or short-term water quality monitoring applications.