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 COx-free hydrogen for fuel cells through its on-site decomposition. The catalysts, composed of nickel as an active metal supported on the Y2O3, were synthesized by the sol-gel self-combustion method conveniently, in which the active metals are uniformly dispersed. 700–1.25Ni1Y1Oα 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·gcat−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 700–1.25Ni1Y1Oα 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 NH3 decomposition.