Milling-Induced Defects in Ni/Zirconia Catalysts for Enhancing Catalytic Activity in Dry Methane Reforming

Alteration of the support structure via milling is a feasible yet rarely applied strategy for boosting the performance of the catalyst in dry methane reforming for syngas production. In this study, we introduce stable oxygen vacancies in the zirconia structure, which enhance the activation of the feedstock, specifically CO₂, while preserving the specific surface area and porosity of the material under reaction conditions. The activity of the tested Ni/ZrO₂ assemblies shows a clear dependence on the milling intensity of ZrO₂, with mild milling at 400 rpm yielding the most active catalyst. At 600 °C, this material achieved the highest feedstock conversion among the tested samples, with 29% for CH₄ and 39% for CO₂. Spectroscopic characterization indicates that the activity of the tested catalysts is controlled by a partial change in the phase composition of the support from monoclinic to tetragonal under reaction conditions, as well as the nature and population of O₂ ^- species, oxygen vacancies, Zr³⁺ defects, and Ni-ZrO₂ interfacial interactions.