Clean hydrogen production from ammonia decomposition over zeolite 13X-supported Ni catalysts

Unlike most H₂ production methods, the decomposition of NH₃ does not result in carbon dioxide emission and is therefore classified as clean technology. Thus, NH₃ holds great promise for the large-scale transportation and storage of H₂, and efficient low-temperature NH₃ decomposition catalysts are highly sought after. Herein, we examined the textural properties and NH₃ decomposition performances of zeolite 13X-supported Ni catalysts prepared by ion exchange, deposition precipitation, and incipient wetness impregnation. The main surface species were identified as Ni phyllosilicates (ion exchange), NiO + Ni phyllosilicates (deposition precipitation), and NiO (impregnation). Compared to other catalysts, the catalyst produced by deposition precipitation achieved the highest H₂ formation rate (22.9 mmol g_cat⁻¹ min⁻¹ at 30 000 mL g_cat⁻¹ h⁻¹, 600 °C) and exhibited a 30-40 °C lower nitrogen desorption temperature. Given that nitrogen desorption is assumed to be the rate-determining step of catalytic NH₃ decomposition, this decrease in the desorption temperature was attributed to improved low-temperature performance. Specifically, the excellent performance of the catalyst obtained by deposition precipitation was ascribed to its large specific surface area and strong metal-support interactions due to the high dispersion and uniform deposition of the active Ni metal on the surface and in the pores of the zeolite support.