Potentiometric Vs. Amperometric Modes for High Temperature Hydrogen BaCe0.6Zr0.3Y0.1O3-Α Sensor
Authors: Abella Jordi , Colominas Sergi , Juhera Eduard , Hinojo Antonio 
Published: May 2020

Fusion energy is considered a source of energy for the near future, due to its no contribution to the greenhouse effect. In a fusion reactor, deuterium and tritium collide and fuse, releasing helium, neutrons and energy. Deuterium can be obtained from water, however tritium must be in situ generated [1]. ITER (International Thermonuclear Experimental Reactor) is being constructed for testing the technology, materials and R&D concepts in order to evaluate its energy gain. One of its goals is to verify the tritium self-sufficiency by breeding systems [2], including the molten Pb-15.7Li eutectic alloy.

In this frame, the chemically aggressive and reducing environment creates the necessity to design new devices for tritium concentration monitoring in the lithium-lead eutectic [3]. For this purpose, electrochemical sensors based on proton-conducting solid-state electrolytes have been proved to be able to operate at high temperatures, with high physical and chemical stabilities. These electrolytes are perovskite phase materials, in which the electrical carriers are positive holes, excess electrons, oxide ion vacancies and interstitial protons, which interact with oxide ions.

Different proton-conducting solid-state electrolytes have been studied previously in the Electrochemical Methods Laboratory at Institut Quimic de Sarria (IQS). These solid electrolytes have been employed in the construction of electrochemical probes that can work on potentiometric and amperometric modes [4]. In the present work, the response of potentiometric and amperometric hydrogen sensors, constructed with BaCe0.6Zr0.3Y0.1O3-α ceramic electrolyte, was compared. The sensors consisted on an open alumina tube with a sealed proton conducting ceramic pellet in one side. Both sides of the pellet were platinized and connected to platinum wires. The wires ends were the positive and the negative poles of the sensor.

Both operating modes were tested at different hydrogen and argon mixtures at the working compartment. In the potentiometric mode, the potential difference between both electrodes was measured and it was compared with the theoretical value calculated from the Nernst equation. In the reference electrode, the hydrogen partial pressure was kept constant during all the experiments. Moreover, the amperometric sensor measured the current through both electrodes when a voltage was applied, obtaining a calibration curve.

References

[1] F. Mannone, ed., Safety in Tritium Handling Technology, Springer Netherlands, Dordrecht, 1993. doi:10.1007/978-94-011-1910-8.

[2] C. Moreno, L.A. Sedano, A Pfd-based 1D model for dynamic and transient tritium transfers between ITER HCLL TBM auxiliary systems, Proc. - Symp. Fusion Eng. (2009) 2–5. doi:10.1109/FUSION.2009.5226409.

[3] F. Barbier, G. Benamati, C. Fazio, A. Rusanov, Compatibility tests of steels in flowing liquid lead–bismuth, J. Nucl. Mater. 295 (2001) 149–156. doi: 10.1016/S0022-3115(01)00570-0.

[4] L. Llivina, S. Colominas, J. Abellà, Evaluation of the response time of H-concentration probes for tritium sensors in lead-lithium eutectic alloy, Fusion Eng. Des. 89 (2014) 1397–1401. doi:10.1016/j.fusengdes.2014.01.034.