In situ Reduction and Oxidation of Nickel fromSolid Oxide Fuel Cells in a Transmission Electron Microscope

摘要

Environmental transmission electron microscopy was used tocharacterize in situ the reduction and oxidation of nickel from aNi/YSZ solid oxide fuel cell anode support between 300-500°C.The reduction is done under low hydrogen pressure. The reductioninitiates at the NiO/YSZ interface, then moves to the center of theNiO grain. At higher temperature the reduction occurs also at thefree NiO surface and the NiO/NiO grain boundaries. The growth ofNi is epitaxial on its oxide. Due to high volume decrease,nanopores are formed during reduction. During oxidation, oxidenanocrystallites are formed on the nickel surface. The crystallitesfill up the nickel porosity and create an inhomogeneous structurewith remaining voids. This change in structure causes the nickeloxide to expand during a RedOx cycle.