COx-free hydrogen production via ammonia decomposition over mesoporous Co/Al2O3 catalysts with highly dispersed Co species synthesized by a facile method

Abstract

Transition metals have been considered as potential catalysts for ammonia decomposition to produce CO_x-free hydrogen for fuel cells. However, the facile synthesis of transition metal catalysts with small size active species, high porosity and good structural stability is still a challenge in catalytic NH₃ decomposition. Herein, mesoporous Co/Al₂O₃ catalysts with various cobalt contents were synthesized by a facile modified sol–gel method. The catalyst 15CoAl with 15 at% cobalt content realizes the optimal catalytic NH₃ decomposition performance. 92% NH₃ conversion at 600 °C is achieved with a gaseous hourly space velocity (GHSV) of 24 000 cm³ g_cat⁻¹ h⁻¹ and a hydrogen formation rate of 33.9 mmol g_cat⁻¹ min⁻¹ at 600 °C is maintained after a 120 h long-duration stability test. Uniform small cobalt particles with high dispersion are well embedded into the skeleton of the mesoporous Al₂O₃ matrix. The aggregation of active cobalt species during the high temperature reaction can be effectively prevented by the mesoporous Al₂O₃ matrix due to the strong interaction between them, thus ensuring a good catalytic performance for ammonia decomposition.