Novel CeO2-based screen-printed potentiometric electrodes for pH monitoring

Abstract

Nuclear waste repositories are being installed in deep excavated rock formations in some places in Europe to isolate and store radioactive waste. In France, the Callovo-Oxfordian formation (COx) is a possible candidate for nuclear waste storage. This work investigates the applicability of CeO 2 -based oxides (CeO 2 , Ce 0.8 Sm 0.2 O 2 and Ce 0.8 Zr 0.2 O 2 ) for monitoring the pH of the COx pore water. The study is limited to the pH range between 5.5 and 13.2, which includes the pH values that have been encountered or are anticipated in the COx formation during its evolution as radioactive waste repository due mainly to alkalinisation, an increase in salinity, a decrease in redox potential. Screen-printing was done to assemble electrodes and rapidly generate data sets. The electrochemical behavior of CeO 2 -based screen-printed electrodes (CeO 2 -based SPEs) was determined by cyclic voltammetry and electrochemical impedance spectroscopy. The use of the electrodes for pH sensing was then evaluated by potentiometric measurements. The feasibility of measuring pH with CeO 2 -based SPEs was first tested in NH 4 Cl/NH 3 buffer solutions, leading to electrode calibration over the widest range of pH, from around neutral to basic pH. Experiments were then conducted in NaHCO 3 /Na 2 CO 3 buffer samples similar to conditions prevailing in the COx formation.Ce 0.8 Zr 0.2 O 2 SPEs exhibit a near-Nernstian behavior (sensitivity -(51±2)mV/pH) in the pH range 5.5-13.2 at 25 °C. Electrode response was slightly affected by the direction of the pH change. Electrode reliability was clearly demonstrated for pH monitoring. Probes based on the same components, but more durably designed, could be considered for pH measurements in radioactive waste repositories.

New Developments in Smart Bandage Technologies for Wound Diagnostics

“…A number of research avenues have been explored to counter these issues and both potentiometric [31][32][33][34][35][36][37][38][39][40][41][42][43][44] and voltammetric [ 16-20 , 45-51 ] methodologies have been pursued. In most cases, a functional material containing pH sensitive components is applied to the surface of an appropriate sensor substrate through a variety of methods that include: Adsorption/monolayer, [ 39,48 ] polymer fi lms, [ 36 ] screen printed inks, [ 35,38,40,47 ] covalent attachment, [ 46,47 ] or electrodeposition. [ 32,33,37,[42][43][44]50 ] Screen printed electrochemical sensors have been designed specifi cally for wound pH monitoring applications and shown to be a versatile addition.…”

A Multi-Parametric Device with Innovative Solid Electrodes for Long-Term Monitoring of pH, Redox-Potential and Conductivity in a Nuclear Waste Repository

“…Our antimony-based SPEs show a near-Nernstian response (an average of −53.6 mV/pH) and thus appear to be suitable electrodes for accurate pH measurements. As pH sensors, the performance level of Sb-based screen-printed electrodes can be compared to that obtained with CeO 2 -based [38] or RuO 2 -based [32] SPEs.…”

“…At the same time, experiments were also conducted on antimony-based screen-printed electrodes (SPEs). The reliability of SPEs has already been demonstrated for various applications in earlier papers: semi-continuous monitoring of trace metals [34], and the development of screen-printed pH electrodes based on ruthenium dioxide [32,35], cobalt oxide [36], phenanthraquinone [37] and, more recently, cerium-oxide [38]. Moreover, screen-printing is a simple and fast method for the large-scale production of reproducible low-cost sensors, which allows quick generation of reliable data [39,40].…”

“…Carbon-based screen-printed electrodes (SPEs) [34,38,40,54], with a working surface of 9.6 mm 2 , were conditioned in a stirred solution containing Sb (III) (10 −2 M SbCl 3 ) and HNO 3 (pH = 0) by applying four cycles of cyclic voltammetry (potential range −0.1 V to +0.8 V, scan rate 100 mVs −1 ). The Sb crystals (Sb 3+ + 3e − → Sb) were then deposited at −0.5 V/SCE during 1600 s. These two steps were performed without removing oxygen from the solution.…”

Disposable Screen Printed Electrochemical Sensors: Tools for Environmental Monitoring

“…Betelu et al , investigated the applicability of CeO 2 -based screen printed electrodes for monitoring the pH of the COx pore water. However, this study was limited to the pH range between 5.5 and 13.2 [50]. Xiong et al designed a calibration-less sensor based on nitrosophenyl-modified edge plane pyrolytic electrodes and screen printed electrodes to monitor pH changes [51].…”