Spontaneous Formation of Asymmetric Oxygen Vacancies in Transition-Metal-Doped CeO<sub>2</sub> Nanorods with Improved Activity for Carbonyl Sulfide Hydrolysis
Shunzheng Zhao, Dongjuan Kang, Yunpeng Liu, Yanfeng Wen, Xizhou Xie, Honghong Yi, Xiaolong Tang
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 CeO 2 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 CeO 2 and formed a solid solution structure. The metal-doped CeO 2 (M/CeO 2 ) showed improved reduction properties, more Ce 3+ and oxygen vacancies in comparison with pure CeO 2 . The introduction of transition metal greatly enhanced activity of M/CeO 2 for COS hydrolysis. Among them, the Co/CeO 2 sample displayed the highest activity and H 2 S selectivity. The roles of metal doping in improving activity were explored on the basis of DFT calculations. The strong interaction between doped metals and CeO 2 promotes the spontaneous formation of asymmetric oxygen vacancies in M/CeO 2 . These asymmetric oxygen vacancies facilitate the activation and dissociation of H 2 O 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.