Minority Bulk and Surface Proton Conduction in Positrodes for Proton Ceramic Electrochemical Cells

The positrode is a critical component for proton ceramic steam electrolyzers and fuel cells for hydrogen and ammonia. It constitutes a major contribution to the over-potentials and hence losses in the whole cell, resulting from its limited solubility and diffusivity of protons, which is challenging to characterise and improve. We are introducing a PhD project that aims to establish theoretical frameworks and experimental methodology for measuring protonic conductivities in the bulk and on surfaces of positrode materials. The approaches to reach the goal comprise the use of defect chemistry and transport theory for protons conduction, with the implementation of physiochemical experiments to distinguish signals of protons among other defects and charge carriers and paths on those predominantly electronic conductors. The results will be used as input to other project participants who perform computer simulations and, on that basis, seek strategies for optimization and effects on electrodes in scaled-up cells.