Potentiometric Response of Ag/AgCl Chloride Sensors in Model Alkaline Medium

Abstract

The stability and reproducibility of an Ag/AgCl sensors’ response in an alkaline medium are important for the application of these sensors in cementitious materials. The sensors’ response, or their open circuit potential (OCP), reflects a dynamic equilibrium at the sensor/environment interface. The OCP response in an alkaline medium is affected by the presence of hydroxide ions. The interference of hydroxide ions leads to inaccuracies or a delay in the sensors’ response to a certain chloride content. In this article, the potentiometric response (or OCP evolution) of the chloride sensors is measured in model solutions, resembling the concrete pore water. The scatter of the sensors’ OCP is discussed with respect to the interference of hydroxide ions at varying chloride concentration in the medium. The deviation of the sensor’s response from its ideal performance (determined by the Nernst law) is attributed to dechlorination of the AgCl layer and the formation of Ag2O on the sensor’s surface. Results from the surface XPS analysis of the AgCl layer before and after treatment in alkaline medium confirm these observations in view of chemical transformation of AgCl to Ag2O.

Silver Nanoneedle Probes Enable Sustained DC Current, Single-Channel Resistive Pulse Nanopore Sensing

“…To further test our hypothesis for the presence of chloride, we calibrated the perchloric acid-etched silver nanoneedles in solutions of different chloride activities and recorded the open circuit potential (OCP). 55,56 The probes exhibited Nernstian behavior in a chloride concentration range of 10 −5 −10 −1 M with a correlation factor (R 2 ) of 0.996 and a gradient of ∼50 mV, in good agreement with the literature values 55−58 (Figure S3).…”

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

“…[15] The typically recommended pH range in which Ag/AgCl REs can be used without risking their integrity is from pH = 1 to 8, given that at higher pH AgCl decomposes to Ag 2 O. [16] Mercury-based Hg/HgO REs are typically employed as stable reference in alkaline media. However, they are relatively expensive and problematic to dispose once they are contaminated or degraded, which may disfavour their use particularly during the screening phase of a project.…”

Embeddable Chloride Sensor for Monitoring Chloride Penetration into Cement Mortar

“…Calibration of a Ag/AgCl sensor is a necessary step in evaluating its performance when in contact with the external medium [19]. The electrode potentials were tested at a constant temperature of 20 ± 2 • C. Saturated Ca(OH) 2 solution with different NaCl concentrations was used to calibrate the Ag/AgCl electrode.…”

“…Climent-Llorca et al [16] reported that a Ag/AgCl electrode embedded in a mortar sample maintained good stability over three months. The preparation methods of Ag/AgCl include the physical powder pressing method [17,18], thermal decomposition method, and constant current anode polarization method [19,20]. The Ag/AgCl electrode prepared by the physical powder compaction method is easily powdered and peeled off, so the conductivity of the electrode becomes poor.…”