The Dual-Active-Site Catalysts Containing Atomically Dispersed Pr³⁺ with Ni/CeO₂ for CO₂ Hydrogenation to Methane

In this study, uniformly dispersed Pr³⁺ as an isolated atom over Ni/CeO₂ catalyst (Ni-Pr/CeO₂) is designed to enhance catalytic activity for CO₂ methanation, achieving an impressive 87% conversion with ≈100% CH₄ selectivity at 300 °C temperature. In contrast, the traditional Ni/CeO₂ and NiPr/CeO₂-imp catalysts exhibit poor conversion and selectivity, highlighting the proof of concept on the advantage of atomic-scale dispersion. Structural analysis via PXRD, XAS, and XPS confirms the successful incorporation of Pr³⁺ into the CeO₂ lattice by creating defects. XPS and XAS studies further reveal a significant increase in oxygen vacancies, a key factor in enhancing catalytic performance at lower reaction temperatures. STEM-EDS analysis confirms the ultra-dispersion of Pr³⁺ (≈7 wt.%) over CeO₂, ensuring a highly active catalyst surface. H₂-TPR and CO₂-TPD results suggest that the Pr³⁺ doping enhances the catalytic activity by decreasing the reduction temperature and increasing basic sites. Additionally, long-term stability tests demonstrate no significant loss in activity over 40 h, confirming the catalyst's robustness and recyclability. This work provides critical insights into the structure-activity relationship of Pr³⁺-modified Ni/CeO₂ catalysts, emphasizing the role of oxygen vacancies in optimizing CO₂ hydrogenation efficiency.