Optimized Co–Ni–Ce–Al Multimetallic Catalyst for Efficient Ammonia Decomposition to Green Hydrogen

Abstract The rising interest in the use of ammonia as a long‐distance hydrogen carrier urges the development of efficient catalysts for its conversion to hydrogen (H 2 ). A highly active multimetallic Co‐Ni‐Ce‐Al catalyst for ammonia decomposition was synthesized via co‐precipitation of these four metals under reflux conditions. The catalytic activity was evaluated in a laboratory reactor using undiluted ammonia feed at atmospheric pressure in a temperature window of 300–600 °C. Systematic variation of the metal molar ratios identified a Co/(Co+Ni) atomic ratio of 0.3 and a Ce/(Al+Ce) ratio of 0.14 to be optimal, achieving 93% ammonia conversion at a temperature as low as 500 °C with a WHSV of 4 h −1 . The catalyst synthesized via co‐precipitation outperformed counterparts synthesized via conventional impregnation methods using alumina and ceria‐alumina supports. This activity enhancement was attributed to the formation of more intimate interfaces using multielement co‐precipitation and improved electronic interactions between cobalt, nickel, and ceria, as revealed by H 2 ‐TPR and STEM‐EDS characterization. Our results underline the importance of the catalyst preparation technique. The Co‐Ni‐Ce‐Al catalyst offers a scalable, cost‐effective alternative to ruthenium catalysts, supporting sustainable hydrogen production via ammonia decomposition.