Influence of niobium on the performance of Ni/CeO₂ catalysts in the dry reforming of methane: Experimental and DFT insight

Dry reforming of methane (DRM) is a promising path to producing syngas by using greenhouse gases; however, in practice, catalyst deactivation and coke formation usually limits its applicability. In the work, a series of Nb-promoted Ni/CeO₂ catalysts were prepared with different metal loadings to explore the influence of niobium on catalytic activity, stability and anti‑carbon-deposition ability. Catalysts were fully characterized by XRD, FTIR, TPR, XPS, SEM EDS, Raman spectroscopy and TPO analysis. The addition of Nb affects the structural and redox characteristics of the catalysts and results in improved metal-support interactions and surface oxygen accessibility. Of the compositions examined, optimized Ni-Nb ratio resulted in an increased activity at lower temperatures and an enhanced stability during continuous operation. The improvement in performance is synergistically owed to the addition of Nb that promotes loads of oxygen vacancies, dispersion of the active sites, and moderates carbon accumulation. Results from DFT computations illustrate that incorporation of Nb into the Ni/CeO₂ structure further facilitates the DRM reaction via two parallel pathways; enhancing the oxophilic behavior of surface lattice O^⁎ sites into adsorbed CH_x species, and lowering energy requirements for the creation of oxgen vacant sites. Enhanced oxygen mobility induced by doping with Nb states enhances catalytic resistance to carbon deposition. It is shown in this work how Nb has the potential to be a structural and electronic promoter to the construction of efficient and stable Ni-based catalysts in DRM applications.