Engineering single-atom Pd sites in ZIF-derived porous Co3O4 for enhanced elementary mercury removal

Abstract

Engineering metal-based nanoarchitectures and their atomic-scale arrangement is a promising avenue for enhanced mercury adsorbent activities. Interactions between metal single atoms and substrates result in regulated transitions between distinct reaction processes that boost mercury adsorption activity. Herein, a novel sorbent of porous Co3O4 with Palladium atomic dispersed was successfully prepared by one-step pyrolysis of zeolitic imidazolate framework 67 (ZIF-67) precursors. Via engineering single Pd atoms into ZIF-derived Co3O4 (Pd1/Co3O4-ZIF), the strong metal-support interaction (SMSI) activated the reducibility of Co3+ in porous Co3O4 to efficiently adsorb and oxidize Hg0, enhancing its mercury removal efficiency. Specifically, Pd1/Co3O4-ZIF exhibited superior sorption performance for Hg0 over a broad range of temperatures (30–350 °C) and high gaseous hourly space velocity (about 555,500 hr−1) with the average Hg0 removal efficiency higher than 98%. The strategy of constructing atomic active sites on the surface of porous metal-oxide to convert adsorbed Hg0 into HgO is a promising approach to solve the problem that Hg0 in flue gas is challenging to remove. Density functional theory (DFT) calculation further proved that the existence of a single Pd site on the surface of Co3O4 significantly reduced the energy barrier of Hg0 to HgO at the atomic level. This work contributed to a thorough comprehension of the structural and adsorption properties of the ZIF-derived Co3O4 sorbent engineering with a single atom and enabled the efficient capture of elemental mercury in flue gas by such ZIF-derived sorbent.