Regulating Oxygen Vacancies for Enhanced Higher Oxygenate Synthesis via Syngas
Xingzhen Qi, Tiejun Lin, Yunlei An, Xinxing Wang, Dong Lv, Zhiyong Tang, Liangshu Zhong
Abstract
Constructing highly efficient dual active sites for preferential formation of higher oxygenates via direct syngas conversion remains a grand challenge. Herein, we reported that the regulation of oxygen vacancy density of metal–oxide support could effectively promote the production of oxygenates. Compared with an inert SiO 2 -supported Co-based catalyst, the rutile TiO 2 -supported catalyst with abundant oxygen vacancies exhibited up to 44.7% CO conversion with the selectivity and space–time yield (STY) of the oxygenate increased to 43.4 wt % and 50 mg g cat. –1 h –1, respectively. Further studies established a nearly linear relationship between the density of the oxygen vacancy and the atomic ratio of Co 2+ /Co 0 or the STY of oxygenated products. Characterization confirmed that the oxygen vacancies not only promote CO adsorption, dissociation, and subsequently the carburization of cobalt species to form Co 2 C but also create a C-rich and H-poor local microchemical environment that benefits CO associative adsorption and C═O bond insertion to form oxygenates. The synergistic effect of oxygen vacancies and the Co 0 /Co 2 C interface site contributed to the observed enhanced performance for direct syngas conversion to higher oxygenates.