Hydrogen production through catalytic ammonia decomposition using Ni-based catalysts supported on yttrium zirconate

Ammonia (NH₃) decomposition to produce hydrogen (H₂) appears as a promising alternative to address the challenges linked to hydrogen storage and transportation. Nonetheless, highly active catalysts based on non-noble metals for its reconversion into H₂ and N₂ are also needed. In this work, a series of Ni-based catalysts supported on yttrium zirconate were prepared by a sol-gel technique, characterized by several techniques (X-ray diffraction, N₂ adsorption-desorption isotherms, thermogravimetric analysis, scanning electron microscopy, temperature programmed reduction and cyclic voltammetry and Fourier-transform infrared spectroscopy) and tested in the ammonia decomposition reaction in the range of 350–700 °C. Apparent activation energies and reaction orders for NH₃ and H₂ were calculated. Ni content (10 %, 15 % and 20 %) and the Y:Zr ratio on the support (1:1 and 2:1) were also experimental variables. For the catalysts with Y:Zr ratio equal 1:1, the catalytic performance rises with the Ni content without significant changes in the apparent activation energy. An increase in the Y:Zr ratio from 1:1 to 2:1 leads to a slightly higher apparent activation energy due to an inhibition of the NH₃ adsorption on the denser and bulkier structure. On the other hand, the increase in the Y:Zr ratio also improves the resistance towards H₂ poisoning, due to a higher number of oxygen vacancies, and mitigates the active phase sintering effect.