Ammonia decomposition over cobalt/carbon catalysts—Effect of carbon support and electron donating promoter on activity

•Highly dispersed ∼2nm cobalt nanoparticles are highly active for ammonia decomposition.•Increasing the degree of graphitisation of the carbon support decreases the catalytic activity of cobalt.•The addition of electron donating promoters has no or detrimental effect on activity of cobalt.•The observations herein oppose those reported for ruthenium-based systems.