Fe-Based Catalysts for the Direct Photohydrogenation of CO_2 to Value-Added Hydrocarbons

摘要

The solar-driven conversion of CO2 into carbon-based fuels and other valuable chemical feedstocks is actively being pursued as an approach for curbing greenhouse gas emissions. Herein, a series of novel Fe-based catalysts with different chemical compositions are successfully fabricated through the hydrogen reduction of MgFeAl-layered double hydroxide nanosheets at temperatures from 300 to 700 degrees C. The catalysts obtained are denoted herein as Fe-x, where x is the reduction temperature in celsius. Fe-500 offers outstanding activity for the photothermal conversion of CO2 to C2+ hydrocarbons under ultraviolet-visible (UV-Vis) irradiation (CO2 conversion 50.1%, C2+ selectivity 52.9%). Characterization studies using X-ray diffraction, extended X-ray absorption fine structure, Mossbauer spectroscopy, and high-resolution transmission electron microscopy determine that the Fe-500 catalyst is comprised of Fe and FeOx nanoparticles on a MgO-Al2O3 mixed metal oxide support. Density functional theory calculations establish that heterostructures consisting of partially oxidized metallic Fe nanoparticles improve the C-C coupling ability of CO2 hydrogenation intermediates, thus enhancing the selectivity to C2+ products. This work introduces a novel photothermal hydrogenation strategy for converting CO2 into valuable chemicals and also opens new avenues toward the development of related solar energy utilization schemes.