Measuring individual overpotentials in an operating solid-oxide electrochemical cell

TL;DR

This paper introduces a non-contact, spatially-resolved method using photo-electrons to measure local overpotentials in a solid-oxide electrochemical cell, enabling direct comparison of electrode efficiencies.

Contribution

It presents a novel in operando measurement technique for local overpotentials in solid-oxide cells, validated against impedance spectroscopy, providing new insights into electrode-specific electro-catalytic activities.

Findings

Ni electrodes favor H2O splitting over H2 oxidation

Pt electrodes favor H2 oxidation over H2O splitting

Method allows direct, spatially-resolved overpotential measurements

Abstract

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.