Structural evolution of carbon deposition on a Ni/YSZ cermet of a SOFC analyzed by soft x-ray XANES spectroscopy

This paper investigated the structural evolution of carbon deposition on a Ni/YSZ cermet of a SOFC. The Ni/YSZ cermet was heated in CH4/Ar environment with a thermobalance. It was observed that carbon deposition preferentially occurred on Ni particles, and the area on which carbon deposited touched the Ni/YSZ interfaces. Meanwhile, carbon deposition was not found on some of the Ni/YSZ interfaces. The Ni/Zr interfaces had various defects, suggesting that the defect pattern may be an important factor for carbon deposition. XANES spectra showed that structural defects and C-H bonds were present in the nascent carbon deposition. As carbon deposition advanced, a graphite structure developed and C-H bonds diminished. Reactants produced from CH4 cracking converted to a nascent amorphous carbon at the Ni/YSZ interface, and then contributed to the growth of carbon deposition on Ni surfaces, leading to the deposition of carbon encapsulating the Ni particles. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.