Multifunctional effect of copper in bimetallic Cu-M/Al2O3 catalysts (M = Fe, Co, and Ni) for NH3 decomposition

Abstract

Ammonia is a promising hydrogen carrier, which can enhance energy transport efficiency when bulk NH3 is transported in a gas carrier vessel. At the end of the NH3 transport, the NH3 gas should be converted to H2 and N2 using NH3 decomposition catalyst, which has outstanding catalytic performance and low cost. The M/Al2O3 and Cu-M/Al2O3 catalysts (M = Fe, Co, and Ni) were test and characterized regarding catalytic NH3 decomposition because we expected the Cu addition could differently change the electronic structure and the desorption behaviors of active metal species. As our expectation, the added Cu modified the catalytic performance and characteristics, but these changes were different, depending on the kind of active metal species (Fe, Co, and Ni). The catalytic activity was improved for Fe/Al2O3 but worsened for Co/Al2O3 and Ni/Al2O3. In addition, the added Cu element acted as an electron donor in Cu-Fe/Al2O3 but as an electron acceptor in Cu-Co/Al2O3 and Cu-Ni/Al2O3 and influenced the desorption behaviors of the generated H and N atoms, particularly in the Cu-Fe/Al2O3, the added Cu alleviated the desorption behaviors of H and N atoms but suppress them in the Cu-Co/Al2O3 and Cu-Ni/Al2O3, which affected the catalytic performance of NH3 decomposition.