Manganese Oxide Modified Nickel Catalysts for Photothermal CO Hydrogenation to Light Olefins

Abstract

AbstractNi‐based catalysts are traditionally considered unsuitable for the Fischer–Tropsch syntheses of olefins, due to the very strong hydrogenation ability of metallic Ni. Herein, this paradigm is challenged. A series of MnO supports nickel catalysts (denoted herein as Ni‐x) are fabricated by H2 reduction of a nickel‐manganese mixed metal oxide at temperatures (x) ranging from 250 to 600 °C. The Ni‐500 catalyst displays unprecedented performance for photothermal CO hydrogenation to olefins, with an olefin selectivity of 33.0% under ultraviolet–visible irradiation. High‐resolution transmission electron microscopy, X‐ray absorption spectroscopy (XAS), and X‐ray diffraction analyses reveal that the Ni‐x catalysts contain metallic Ni nanoparticles supported by MnO. X‐ray photoelectron spectroscopy and XAS establish that electron transfer from MnO to the Ni0 nanoparticles is responsible for modifying the electronic structure of nickel (creating Niδ− states), thereby shifting the CO hydrogenation selectivity toward light olefins. Further, density functional theory calculations show that this electron transfer lowers the adsorption energies of olefins on Ni surfaces, thus minimizing the undesirable deep hydrogenation reactions to higher alkanes. This study conclusively demonstrates that MnO‐modified Ni‐based catalyst systems can be highly selective for CO hydrogenation to light olefins.