Effect of Ammonia Catalytic Decomposition Coating on Electrochemical Performance in Direct Ammonia Solid Oxide Fuel Cells
Yuchen Ya, Yishu Xu, Yimin Liu, Boyu Sun, Junjia Liu, Xiaobei Cheng
Abstract
The effective ammonia decomposition on the anode surface directly impacts direct ammonia solid oxide fuel cell (DA-SOFC) performance. This paper uses electrochemical impedance spectroscopy and Tafel curve to study the impact of directly coating 30 μm Fe catalyst layer (Fe//SOFC) on performance and electrode reaction of DA-SOFC. The electrochemical performances of H 2, NH 3, and NH 3 d.e.g (75% H 2 + 25% N 2 ) were compared within the temperature range of 550–700 °C. The results indicate that, when NH 3 is used as fuel in SOFC, NH 3 decomposition causes significant performance loss of the cell, especially during low-temperature operation. In Fe//SOFC, the decomposition rate of NH 3 is notably enhanced. The high porosity of the catalytic layer has an aggregation effect on the reaction gas, increasing the reactant concentration near the active sites. This reduces the mass transport loss of the cell by 50%, doubles the exchange current density, and significantly improves the cell performance (close to 20%). Nevertheless, the directly coated Fe catalytic layer covers some active sites and pores on the electrode surface, increasing the polarization resistance and the ion transport resistance.