Carbon and Oxygen Double Defects-Enhanced Ru-Based Catalyst for Ammonia Decomposition

Abstract

Although ammonia is widely recognized as one of the most promising candidates for hydrogen storage and transformation, the catalytic mechanisms involved in ammonia decomposition remain insufficiently understood, and the stability of catalysts continues to present significant challenges. In this study, Ru/CeO₂-CNTs catalysts with double defect sites were synthesized by a straightforward method, achieving an outstanding hydrogen production rate of 2230 mmol⁻¹ g_Ru⁻¹ min⁻¹ at 500 °C, outperforming most Ru-based catalysts. Experimental characterization and theoretical calculations revealed that the CeO₂-CNTs interface promotes the formation of oxygen vacancies (O_v) and carbon defects (C_d) through carbon–oxygen interactions. These defects enhance electron transfer from the support to Ru nanoparticles (NPs), modulate NH₃ adsorption and activation and modulate the recombination and desorption of adsorbed N species (N*). Moreover, the coating of CeO₂ significantly improved the stability of CNTs, which weakens undesired reactions under high-temperature and hydrogen-rich conditions. The study introduced a rational design strategy that enhances the multiple elementary stages of the NH₃ decomposition by constructing double defect sites and offering new insights into the design of efficient and durable catalysts under harsh environments.