•Low temperature (450K) hydrogen production from ammonia to unlock its potential as energy vector.•Highly conductive supports (graphitized CNT’s) allows distance electronic modification by promoter.•Synergetic effect of promoter and support enhances low temperature activity. Display omitted Low temperature hydrogen production via ammonia decomposition is achieved by the synergetic combination of a highly conductive support and an electron donating promoter in a ruthenium-based system, with activity at temperatures as low as 450K. The high conductivity of graphitized carbon nanotubes allows for greater electronic modification of the ruthenium nanoparticles by cesium located in close proximity but without direct contact, avoiding the blockage of the active sites. This development of low temperature catalytic activity represents a breakthrough toward the use of ammonia as chemical storage for in-situ hydrogen production in fuel cells.