We use photo-electrons as a non-contact probe to measure local electrical potentials in a solid-oxide electrochemical cell. We characterize the cell in operando at near-ambient pressure using spatially-resolved X-ray photoemission spectroscopy. The overpotentials at the interfaces between the Ni and Pt electrodes and the yttria-stabilized zirconia (YSZ) electrolyte are directly measured. The method is validated using electrochemical impedance spectroscopy. Using the overpotentials, which characterize the cell's inefficiencies, we compare without ambiguity the electro-catalytic efficiencies of Ni and Pt, finding that on Ni H_2O splitting proceeds more rapidly than H2 oxidation, while on Pt, H2 oxidation proceeds more rapidly than H2O splitting.
@article{arxiv.1003.0035,
title = {Measuring individual overpotentials in an operating solid-oxide electrochemical cell},
author = {Farid El Gabaly and Michael Grass and Anthony H. McDaniel and Roger L. Farrow and Mark A. Linne and Zahid Hussain and Hendrik Bluhm and Zhi Liu and Kevin F. McCarty},
journal= {arXiv preprint arXiv:1003.0035},
year = {2017}
}