Spontaneous Formation of Asymmetric Oxygen Vacancies in Transition-Metal-Doped CeO₂ Nanorods with Improved Activity for Carbonyl Sulfide Hydrolysis

Abstract

Introducing oxygen vacancies into metal oxides is a promising strategy to promote their catalytic activity, which has been extensively studied in heterogeneous catalysis. Herein, transition metal (M = Fe, Co, and Ni) doping was used to introduce oxygen vacancies in CeO2 and promote activity for carbonyl sulfide (COS) hydrolysis. Various techniques were performed to accurately characterize the catalyst structure and state. The transition metals successfully entered the crystal lattice of CeO2 and formed a solid solution structure. The metal-doped CeO2 (M/CeO2) showed improved reduction properties, more Ce3+ and oxygen vacancies in comparison with pure CeO2. The introduction of transition metal greatly enhanced activity of M/CeO2 for COS hydrolysis. Among them, the Co/CeO2 sample displayed the highest activity and H2S selectivity. The roles of metal doping in improving activity were explored on the basis of DFT calculations. The strong interaction between doped metals and CeO2 promotes the spontaneous formation of asymmetric oxygen vacancies in M/CeO2. These asymmetric oxygen vacancies facilitate the activation and dissociation of H2O and generation of active hydroxyls, which contributes to the enhanced activity for COS hydrolysis. This work provides an attractive method for obtaining nonprecious metal catalysts for COS hydrolysis.