Iron promoted MOF-derived carbon encapsulated NiFe alloy nanoparticles core-shell catalyst for CO2 methanation

Abstract

The highly ordered and designable properties of MOFs make them competitive precursors to constructing high-performance catalysts for CO2 methanation, however, only a few studies have investigated the facilitation effect of promoters. Herein, a series of carbon encapsulated NiFe alloy nanoparticles core-shell catalysts (NixFe@C, x refers to the ratio of Ni to Fe) were successfully prepared by a method of pyrolyzing Ni-MOF-74 after impregnation in Fe3+ solution for CO2 hydrogenation to CH4, and their composition and structural characteristics were explored in detail by PXRD, N2 adsorption/desorption measurements, TEM, and XPS, etc. Fe-doped catalysts exhibited significantly enhanced CO2 methanation activity compared to the monometallic Ni catalysts, especially Ni7Fe@C, which reached 72.3 % CO2 conversion with CH4 selectivity of 99.3 % at 350 °C, and showed a CO2 conversion of 53.3 % at 300 °C, twice that of Ni@C. The specific effects of the Fe addition on the composition and structure of the catalysts were also investigated via a combination of experiments and DFT calculations, which indicates that appropriate incorporation of Fe was conducive to promoting the dispersion of metal particles and the adsorption ability of CO2 and CO, and thus resulted in significantly improved catalytic performance. This work provides a promising route for the rational design of MOF-derived CO2 methanation catalysts and makes a new attempt to investigate the influence of promoters.