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Effects of Cobalt Addition on the Catalytic Activity of the Ni-YSZ Anode Functional Layer and the Electrochemical Performance of Solid Oxide Fuel Cells

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journal contribution
posted on 24.09.2014, 00:00 by Ting Guo, Xiaolei Dong, Mandar M. Shirolkar, Xiao Song, Meng Wang, Lei Zhang, Ming Li, Haiqian Wang
The effects of cobalt (Co) addition in the Ni-YSZ anode functional layer (AFL) on the structure and electrochemical performance of solid oxide fuel cells (SOFCs) are investigated. X-ray diffraction (XRD) analyses confirmed that the active metallic phase is a Ni1–xCox alloy under the operation conditions of the SOFC. Scanning electron microscopy (SEM) observations indicate that the grain size of Ni1–xCox increases with increasing Co content. Thermogravimetric analyses on the reduction of the Ni1–xCoxO-YSZ powders show that there are two processes: the chemical-reaction-controlled process and the diffusion-controlled process. It is found that the reduction peak corresponding to the chemical-reaction-controlled process in the DTG curves moves toward lower temperatures with increasing Co content, suggesting that the catalytic activity of Ni1–xCox is enhanced by the doping of Co. It is observed that the SOFC shows the best performance at x = 0.03, and the corresponding maximum power densities are 445, 651, and 815 mW cm–2 at 700, 750, and 800 °C, respectively. The dependence of the SOFC performance on the Co content can be attributed to the competing results between the decreased three-phase-boundary length in the AFL and the enhanced catalytic activity of the Ni1–xCox phase with increasing Co content.