This study explores the development of highly loaded bimetallic iron-cobalt catalysts for the catalytic decomposition of ammonia to release hydrogen. The researchers found that combining iron with cobalt in a bimetallic catalyst can overcome the low activity of inexpensive iron catalysts, which suffer from a strong iron-nitrogen binding energy compared to more active metals like ruthenium. Theoretical calculations and *operando* spectroscopy revealed that cobalt suppresses bulk-nitridation of iron and stabilizes the active state. The catalysts are synthesized from Mg(Fe,Co)₂O₄ spinel pre-catalysts with variable Fe:Co ratios through co-precipitation, calcination, and reduction. The resulting Fe-Co/MgO catalysts, with an extraordinary high metal loading of 74 wt.%, combine the advantages of a ruthenium-like electronic structure with a bulk catalyst-like microstructure. The production of ammonia via the Haber-Bosch process is a significant industrial process, but its reverse reaction, ammonia decomposition, has limited industrial applications. The study highlights the potential of Fe-based catalysts for ammonia decomposition, which are commercially attractive due to their lower cost compared to Ru-based catalysts. The researchers identified nitridation as the rate-determining step in ammonia decomposition and demonstrated that alloying iron with cobalt can suppress this step and reduce the nitrogen binding energy, leading to higher activity and stability. The catalytic performance of the Fe-Co/MgO catalysts was evaluated, showing a significant improvement in ammonia conversion and hydrogen production compared to monometallic Fe/MgO catalysts. DFT calculations further supported the findings, indicating that the bimetallic catalysts have nitrogen binding energies closer to the optimal range for ammonia decomposition. This work provides a simple and general approach to fabricating highly active and stable catalysts for ammonia decomposition using alloying with metals with weak nitrogen adsorption energy.This study explores the development of highly loaded bimetallic iron-cobalt catalysts for the catalytic decomposition of ammonia to release hydrogen. The researchers found that combining iron with cobalt in a bimetallic catalyst can overcome the low activity of inexpensive iron catalysts, which suffer from a strong iron-nitrogen binding energy compared to more active metals like ruthenium. Theoretical calculations and *operando* spectroscopy revealed that cobalt suppresses bulk-nitridation of iron and stabilizes the active state. The catalysts are synthesized from Mg(Fe,Co)₂O₄ spinel pre-catalysts with variable Fe:Co ratios through co-precipitation, calcination, and reduction. The resulting Fe-Co/MgO catalysts, with an extraordinary high metal loading of 74 wt.%, combine the advantages of a ruthenium-like electronic structure with a bulk catalyst-like microstructure. The production of ammonia via the Haber-Bosch process is a significant industrial process, but its reverse reaction, ammonia decomposition, has limited industrial applications. The study highlights the potential of Fe-based catalysts for ammonia decomposition, which are commercially attractive due to their lower cost compared to Ru-based catalysts. The researchers identified nitridation as the rate-determining step in ammonia decomposition and demonstrated that alloying iron with cobalt can suppress this step and reduce the nitrogen binding energy, leading to higher activity and stability. The catalytic performance of the Fe-Co/MgO catalysts was evaluated, showing a significant improvement in ammonia conversion and hydrogen production compared to monometallic Fe/MgO catalysts. DFT calculations further supported the findings, indicating that the bimetallic catalysts have nitrogen binding energies closer to the optimal range for ammonia decomposition. This work provides a simple and general approach to fabricating highly active and stable catalysts for ammonia decomposition using alloying with metals with weak nitrogen adsorption energy.