Proton conductivity near room temperature in hydrated pyrochlore-derived materials

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Research on proton-conducting oxide ceramics focuses strongly on materials with the perovskite structure that can be used as the electrolyte in fuel cells operating at temperatures above 400 °C. High-performance, proton-conducting ceramic materials for other electrochemical applications (e.g. as an electrochemical mechanical actuator operating at room temperature or just above) are currently not available. The primary objective of this project is to identify and optimise a high-performance, proton-conducting material for use below 250 °C. We will focus on materials with a disordered pyrochlore structure, with the general composition A2B2O7, where A = Sc, Y or a lanthanide, and B = Zr, Ce or Hf. In contrast to the perovskite-structured proton conductors, disordered pyrochlores received relatively little attention, despite their high chemical stability to CO2. Through a judicious combination of atomistic modelling techniques and macroscopic and microscopic experimental studies, we will: a) derive a comprehensive model of proton conductivity in these materials and use it to predict the desired properties; b) develop protocols to prepare and hydrate ceramics and thin films of these materials; c) measure and understand the nature of their conductivity, and their electrochemical stability window; d) identify the compositions, including possible dopants that maximize proton conductivity. At a higher level, the project will deepen fundamental knowledge in the field of proton conductors and also of order-disorder transitions in pyrochlore-related structures. In addition to the traditional applications of proton conductors, this project will contribute to the emerging field of solid-state chemotronics ranging from MEMS to adaptable surfaces and to Si-integrated proton batteries.