Microwave versus hydrothermal synthesis of Ni–La catalysts for dry reforming of methane: Exploring the structure-activity relationships

Dry reforming of methane (DRM) over Ni-based catalysts is often limited by metal sintering and carbon deposition, making the control of precursor structure and activation pathway crucial for catalyst durability. In this work, Ni–La catalysts were prepared through hydrothermal (HT) and microwave-assisted (MW) routes, combining either one-pot Ni incorporation or post-synthesis impregnation. Structure-function relationships were investigated by synchrotron XRPD/PDF coupled with principal component analysis (PCA), operando XRPD/XAS, H2-TPR, TEM/HAADF-STEM-EDS, and TGA. The results show that both the synthesis route and the Ni incorporation strategy strongly affect the organization of the La–Ni–O precursor network, thereby governing reducibility, Ni dispersion, carbon formation, and catalytic behavior under DRM conditions. Ex situ XRPD/PDF and TEM reveal that MW-derived materials develop smaller, more homogeneous La–Ni–O domains than the corresponding HT samples, while one-pot preparation promotes a more integrated catalyst architecture than impregnation. Operando analyses indicate that the main structural transformation occurs during the reduction step, whereas only limited changes take place under reaction conditions. Catalytic tests suggest that MW-derived catalysts exhibit higher activity and improved stability, with the one-pot sample showing the most favorable overall performance. These findings highlight the central role of precursor architecture in determining the properties of the active catalyst and provide useful design criteria for the development of more robust Ni-based systems for DRM and greenhouse-gas valorization.