Oxygen vacancy-rich Pr₆O₁₁: unlocking superior catalytic support for efficient ammonia synthesis

Developing effective support materials is crucial for enhancing the performance of transition metal-based catalysts, thereby enabling efficient ammonia synthesis under mild conditions. In this study, we synthesized a series of praseodymium oxides (Pr₆O₁₁) with exceptionally high oxygen vacancy concentrations (up to 74%) after activation and demonstrated their potential as robust supports for Ru-based catalysts. By leveraging the regrowth of Pr(OH)₃, high-index facets were introduced, resulting in the formation of abundant oxygen vacancies in the final Pr₆O₁₁ structures. The Ru/Pr₆O₁₁ catalysts exhibited outstanding performance in ammonia synthesis, characterized by high catalytic activity and strong resistance to H₂ poisoning. Under reaction conditions of 400 °C and 0.1 MPa, the 2 wt% Ru/Pr₆O₁₁ catalyst achieved an ammonia production rate of 4.4 mmol g⁻¹ h⁻¹ and maintained this performance for over 100 hours, significantly outperforming Ru catalysts supported on other oxides. Furthermore, the 5 wt% Ru/Pr₆O₁₁ catalyst demonstrated exceptional long-term stability, operating continuously for more than one month. These findings underscore the potential of Pr₆O₁₁-supported Ru catalysts for advancing efficient and durable ammonia synthesis.