Heterogeneous Catalyst-Modified Anode in Solid Oxide Fuel Cells for Simultaneous Ammonia Synthesis and Energy Conversion

An innovative and cost-efficient method of coproduction of electricity and ammonia through solid oxide fuel cells (SOFCs) by implementing a transition metal nitride (MnxNy) catalyst on the fuel electrode is the focus of the work. Breaking molecular nitrogen (N equivalent to N) with a simultaneous enhancement in the electrochemical performance of the Ni-ScSZ-supported-SOFC was achieved by using transition metal nitride (Mn4N) catalysts on the fuel electrode. Ex situ X-ray diffraction and X-ray photoelectron spectroscopy revealed the chemical stability of the MnxNy catalyst under H-2 and N-2 atmospheres under cell operating conditions. The nitrogen reduction reaction (NRR) at the Mn4N active sites was measured via hydrogenation of lattice nitrogen and formation of metallic Mn followed by renitrification of the catalyst. Electrochemical impedance spectroscopy analysis of the catalyst-modified cell revealed improved hydrogen oxidation reaction activity and NRR during cell operation. The cell exhibited peak power densities of 539 and 374 mW center dot cm(-2) for humidified (3 wt %) H-2 and a dry N-2/H-2 (1:1) mixture, respectively. Furthermore, a high rate of ammonia production of 1.63 x 10(-9) mol center dot cm(-2)center dot s(-1) and a power density of 348 mW center dot cm(-2) were achieved when the cell was operated at 800 degrees C.