Direct Conversion of Ammonia to Electricity on a PCFC and an SOFC

A protonic ceramic fuel cell (PCFC) and a solid oxide fuel cell (SOFC) using NiO/BZCY and NiO/YSZ anodes, respectively, were compared in H₂ and NH₃ fuels at 600 °C. The effect on the cell performance by adding lanthanum strontium ruthenium titanate (LSRT) into the anode were investigated. The performance of PCFCs in NH₃ was found to resemble that in H₂ and remain stable; by contrast, the SOFC was subject to a rigorous fluctuation of voltages in NH₃, followed by performance loss. Surface characterization evidenced that phase separation between nickel and electrolyte YSZ is a major reason to the deactivation of SOFCs. The structure degradation occurred due to repetitive nitridation of nickel and subsequent oxidation reaction. Despite containing nickel in the anode too, the PCFC experienced the little effect since the oxidation reaction occurs at the cathode. Furthermore, the addition of the LSRT helped stabilize the PCFC anode by facilitating decomposition of ammonia with exsolved ruthenium sites, which are characterized by temperature programmed reaction studies.