CFCC wins program to study hydrogen uptake in ceramic proton conductors

The Colorado Fuel Cell Center was awarded four days of “beam time” at the National Institute of Standards Neutron Imaging Facility. The effort is entitled “Elucidation of Protonation and Transport Processes in Proton Conducting Ceramics,” and seeks to advance our understanding of the ionic and electronic transport processes through protonic ceramics. Development of these novel protonic-ceramic materials (such as BaZr0.6Ce0.2Y0.2O3-d) is hindered by the complex interrelationship between the multiple charge carriers which may be present in the material. These multiple charge carriers include protons, oxygen ions, holes and potentially electrons; the role of each is highly dependent on operating conditions, including temperature and gas conditions. The proposed experiments will use isotopic contrast variation to definitively measure the proton concentration profile as a function of membrane current density for a range of electric and chemical potential driving forces on an operating membrane.

Schematic of proton-conducting ceramic fuel cell under test.  Proton transport is represented as OH•.

Schematic of proton-conducting ceramic fuel cell under test. Proton transport is represented as OH•.

Colleagues at Mines have proposed protonation and conduction models and have validated these predictions against indirect electrochemical measures. However, given the parallel charge carrier pathways in these materials, in operando measurements are needed to directly verify proposed theories. By imaging the operating membrane in both H2O and D2O environments, important insights can be made about the protonation mechanism and the charge transport pathways in this important class of materials. Operating at 600 °C, measurements will be taken on dense protonic-ceramic membranes operating in a variety of different chemical environments (a mixture with varying amounts of H2 and H2O on the “Hydrogen side” (i.e., anode), and air on the cathode), and different electric potential differences across the membrane to differentiate between the proton diffusivity and conductivity. Precise measurements of the hydrogen concentration profiles will then be correlated with parallel, offline flux measurements (using current measurements and mass spectrometry) to definitively determine transport mechanisms in this important class of materials.

The effort begins in 2017. The Primary Investigator on the program is Assistant Professor Steven DeCaluwe, with Associate Professor Neal P. Sullivan serving as Co-PI. Both faculty are members of the Mechanical Engineering Department.