Catalyst support effect on ammonia decomposition over Ni/MgAl2O4 towards hydrogen production

Abstract

Ammonia is a prospective fuel for hydrogen storage and production, but its application is limited by the high cost of the catalysts (Ru, etc.) to decompose NH3. Decomposing ammonia using non-precious Ni as catalysts can therefore improve its prospects to produce hydrogen. This work proposes several Ni/MgAl2O4 with the support properties tuned and investigates the support effect on the catalytic performance. Ni/MgAl2O4-LDH shows high NH3 conversion (∼88.7%) and H2 production rate (∼1782.6 mmol g−1 h−1) at 30,000 L. kg−1 h−1 and 600 °C, which is 1.68 times as large as that of Ni/MgAl2O4-MM. The performance remains stable over 30 h. The characterizations manifest that the high specific surface area of Ni/MgAl2O4-LDH can introduce highly dispersed Ni on the surface. Kinetics analysis implies promoted NH3 decomposition reaction and alleviated H2 poisoning for Ni/MgAl2O4-LDH. A roughly linear relationship is obtained by fitting the curves of dispersed Ni on the surface vs the reaction orders regarding H2 and NH3. This indicates that enhanced NH3 decomposition performance can be ascribed to the strengthened NH3 decomposition reaction and weakened H2 poisoning by the highly dispersed Ni on the MgAl2O4-LDH surface. This work provides an opportunity to develop highly active and cost-effective catalysts to produce hydrogen via NH3 decomposition.