Self-assembled geopolymer-based microspheres supported nanoclusters for CO2 hydrogenation

Abstract

Loading noble metals into alkali metal-rich adsorbents for carbon recovery is a promising strategy to improve the environment. In this work, self-assembled metakaolin-based geopolymer microspheres GNaA were prepared by a one-pot suspension solidification method, and then Ni(II), Pd(II) or Pt(IV) was adsorbed. M-GNaA (M = Ni1, Ni5, Pd1, Pd5, Pt1, Pt5) were successfully prepared as supported catalysts for the hydrogenation of CO2, and their catalytic performance was compared. The adsorbed Ni, Pd or Pt formed highly dispersed nanoparticles under the action of alkali metals in geopolymer. Pt5-GNaA maintained the original dispersed state even after multiple cycles and long-term testing. The results show that the size of Pt particles can be adjusted and that the large-area agglomeration of active metals can be inhibited by Na+ in geopolymer. The presence of −OH in geopolymer makes the Pt nanocluster reaction approximate to a single-atom reaction. These findings indicate that it is feasible to rationally design catalyst activity and chemoselectivity by using geopolymer to support nanoclusters for CO2 hydrogenation.