Fig. 3: Oxidation and reduction cycling of a Ni grain depending on the O2-to-H2 ratio and resulting voltage measured across the SOFC sample.
From: Operando analysis of a solid oxide fuel cell by environmental transmission electron microscopy

a Contour plot of the evolution of the TEM image intensity taken along the arrow shown in b, the residual gas analyser (RGA) O2-to-H2 ratio (raw data, full line, and shifted forward by 180 seconds, dashed line), and open circuit voltage measured between the anode and cathode (raw and gaussian-filtered data). b–g Selection of TEM images of the edge of a Ni grain at the critical steps of the reoxidation and reduction processes. Black arrows and arrowheads highlight key morphological changes occurring at the surface of the Ni grain, as discussed in the text.