title: Effects of cobalt addition on the catalytic activity of the Ni-YSZ anode functional layer and the electrochemical performance of solid oxide fuel cells.
abstract: 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 Ni(1-x)Co(x) alloy under the operation conditions of the SOFC. Scanning electron microscopy (SEM) observations indicate that the grain size of Ni(1-x)Co(x) increases with increasing Co content. Thermogravimetric analyses on the reduction of the Ni(1-x)Co(x)O-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 Ni(1-x)Co(x) 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 Ni(1-x)Co(x) phase with increasing Co content.
authors.affiliation: Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China , 96 Jinzhai Road, Hefei, Anhui 230026, P. R. China.
authors.forename: Ting
authors.initials: T
authors.lastname: Guo
authors.forename: Xiaolei
authors.initials: X
authors.lastname: Dong
authors.forename: Mandar M
authors.initials: MM
authors.lastname: Shirolkar
authors.forename: Xiao
authors.initials: X
authors.lastname: Song
authors.forename: Meng
authors.initials: M
authors.lastname: Wang
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.forename: Ming
authors.initials: M
authors.lastname: Li
authors.forename: Haiqian
authors.initials: H
authors.lastname: Wang
keywords: anode functional layer; catalytic; nickel−cobalt alloy; solid oxide fuel cells; thermogravimetric analyses; three-phase boundary