(653e) Electrocatalytic Synthesis of Ammonia on Composite Bimetallic Nitride-Perovskite Oxide Soec Cathode | AIChE

(653e) Electrocatalytic Synthesis of Ammonia on Composite Bimetallic Nitride-Perovskite Oxide Soec Cathode


Ferree, M. - Presenter, The Ohio State University
Gunduz, S., The Ohio State University
Kim, J., The Ohio State University
Co, A., The Ohio State University
Ozkan, U., The Ohio State University
In the past century, the human population has become increasingly dependent on commercial NH3 production to grow food, but the technology has evolved very little to keep up with the accelerating demand. In the conventional Haber-Bosch process, N2 and H2 are reacted at high temperatures and pressures, but the H2 production and pressurization steps can be bypassed by using N2 and H2O in a solid-oxide electrolysis cell (SOEC). Perovskite oxides are known to be active cathode materials for high-temperature electrolysis of H2O, but certain transition metal nitrides may be more capable of activating N2.

In this study, a composite SOEC cathode of the perovskite (La0.6Sr0.4)0.95Co0.2Fe0.8O3 (LSCF) and the nitride Co3Mo3N was fabricated, and its activity for NRR was studied. A layer of LSCF was sintered on both sides of the YSZ electrolyte, and a mixture of Co3Mo3N and LSCF was deposited on the cathode side. During NRR, 3% H2O/N2 was supplied to the cathode at 500–600°C with applied current densities of 0–2 mA/cm2. NRR activity was quantified, and the measured production rates were corrected by Ar and OCV control experiments. The composite cathode performed significantly better than the pure perovskite cathode or pure Co3Mo3N cathode, indicating a synergistic relationship between the two materials. These results imply that Co3Mo3N increases the rate of nitrogen activation, while the ionic/electronic conduction properties of LSCF improve the overall cell performance. Relevant properties of Co3Mo3N were analyzed such as electronic conductivity, stability in the reaction environment, and mobility of nitrogen ions. Co3Mo3N was characterized by in­-situ XRD, NAP-XPS, XANES, and temperature-programmed experiments.

Few non-noble metal materials have been identified as effective electrochemical NRR catalysts for the high-temperature range. The activity and stability of Co3Mo3N and its compatibility with proven perovskite catalysts allow for this unique composite cathode approach to high temperature NH3 production.