Carbon-free H₂ production from ammonia triggered at room temperature with an acidic RuO₂/γ-Al₂O₃ catalyst

Ammonia has been suggested as a carbon-free hydrogen source, but a convenient method for producing hydrogen from ammonia with rapid initiation has not been developed. Ideally, this method would require no external energy input. We demonstrate hydrogen production by exposing ammonia and O₂ at room temperature to an acidic RuO₂/γ-Al₂O₃ catalyst. Because adsorption of ammonia onto the catalyst is exothermic, the catalyst bed is rapidly heated to the catalytic ammonia autoignition temperature, and subsequent oxidative decomposition of ammonia produces hydrogen. A differential calorimeter combined with a volumetric gas adsorption analyzer revealed a large quantity of heat evolved both with chemisorption of ammonia onto RuO₂ and acidic sites on the γ-Al₂O₃ and with physisorption of multiple ammonia molecules.