Low–Temperature Ammonia Decomposition Catalysts for Direct Ammonia Solid Oxide Fuel Cells
Yuanhui Wang, Jun Yang, Jianxin Wang, Wanbing Guan, Bo Chi, Lichao Jia, Jieyu Chen, Hiroki Muroyama, Toshiaki Matsui, Koichi Eguchi
Abstract
Ammonia is regarded as a promising alternative fuel for solid oxide fuel cells (SOFCs) compared with hydrogen due to its low cost and ease for transportation and storage. The conventional anode Ni/yttria-stabilized zirconia (Ni/YSZ) of SOFCs can serve as an efficient catalyst for ammonia decomposition at high temperatures above 700 °C but its catalytic activity decreases rapidly at lower temperatures, leading to an undesirable degradation of cell performance. Here we report a low-temperature ammonia decomposition catalyst Ba-modified Ni/yttria-stabilized zirconia (Ba-Ni/YSZ) prepared by a one-pot solid-liquid (SL) method. Enhanced performance can be obtained for Ba-Ni/YSZ compared with that of Ni/YSZ catalysts, indicating that the addition of Ba promotes the catalytic activity. X-ray photoelectron spectroscopy (XPS) and Temperature-programmed reduction with H 2 (H 2 -TPR) characterizations of Ba-Ni/YSZ catalysts indicate that Ba changes the electronic structure of Ni and facilitates the interaction between Ni and support. The kinetics analysis demonstrates that the modification by a small amount of Ba species alleviated the negative effect of the hydrogen poisoning on the active sites of Ni/YSZ catalysts. Besides, the Ba-Ni/YSZ catalyst is introduced into the flat-tube SOFC with symmetric double-sided cathodes (DSC), and significantly improves the electrochemical performance of directly ammonia-fed DSC cells at low temperatures.