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The hollow hierarchical structure Cu@S and CuFe0.5@S catalysts were successfully synthesized through the “dissolution-recrystallization” (D-R) method for the reverse water gas shift reaction (RWGS). The encapsulated catalysts had a hierarchical porous structure and better dispersion of Cu particles than the Cu-S and CuFe0.5-S samples prepared via the conventional impregnation method. Furthermore, CuFe0.5-S and CuFe0.5@S catalysts showed higher CO2 conversion and 100% selectivity of CO at the entire temperature range investigated in this work compared to the monometallic catalysts Cu-S and Cu@S. Interestingly, the reaction activity of all the samples increased according to the sequence: CuFe0.5@S > CuFe0.5-S > Cu@S > Cu-S at 400–550 °C under atmospheric pressure. These results indicate that the higher dispersion of encapsulation structure and the enhanced surface basicity derived from the addition of Fe play crucial roles in enhancing the catalytic performance of Cu-based catalysts in the RWGS reaction.

A nano-hollow zeolite-encapsulating ultra-fine Fe nanoparticle catalyst denoted as Fe@n-hS-HT was successfully synthesized through a simple water steam treatment of the Fe@n-hS catalyst prepared by the “dissolution–recrystallization” (D-R) method. The Fe@n-hS-HT catalyst had a hierarchical porous structure and a high dispersion of Fe2O3 particles with a size of 3.4 nm. Furthermore, the results of several characterization methods, such as XRD, HAADF-STEM, and H2-TPR, further demonstrated the transformation of the skeleton Fe in Fe@n-hS into Fe2O3, which was uniformly dispersed in the Fe@n-hS-HT catalyst. Meanwhile, Fe@n-hS-HT had significantly higher selectivity and yield of C2-C4= than the reference catalysts Fe/S and Fe@n-hS, which provided strong proof for the confined catalysis of the metal@zeolite catalyst.