Efficient Ni/Y2O3 catalyst prepared by sol-gel self-combustion method for ammonia decomposition to hydrogen

Ammonia has sparked a lot of interest as a promising hydrogen carrier for the development of renewable energy and as a workable method to produce CO x -free hydrogen for fuel cells through its on-site decomposition. The catalysts, composed of nickel as an active metal supported on the Y 2 O 3 , were synthesized by the sol-gel self-combustion method conveniently, in which the active metals are uniformly dispersed. 700–1.25Ni 1 Y 1 O α exhibits the best catalytic activity and has the most active metal dispersion (6.15 %). The ammonia conversion can reach 96 % at 550 °C and 12000 ml·g cat −1 ·h −1 gas hourly space velocities (GHSVs) as well as 100 % at 600 °C and the same GHSVs. Temperature-programmed reduction, temperature-programmed desorption, and X-ray photoelectron spectroscopy were used to characterize the catalysts. It was found that 700–1.25Ni 1 Y 1 O α has the best capacity for hydrogen desorption resulting in weakening the inhibitory effect of hydrogen to the reaction and enhancing the reactivity of the catalyst. The electron transfer from Y in Y–O–Ni structure increases gradually as the Ni to Y ratio becomes appropriate, enhancing the alkalinity of the catalyst and electron density around the Ni, which is beneficial to NH 3 decomposition.