A novel self-assembly approach for synthesizing nanofiber aerogel supported platinum single atoms†
A great challenge in catalyst engineering is precisely assembling and positioning nanoscale active metals at desired locations while constructing robust functional architectures. This article presents a novel approach for constructing macroscopic Ag-doped manganese oxide aerogels (up to 2 L) while homogeneously incorporating active Pt single atoms (Pt/Ag-MnO2) based on a solution–solid–solid (SSS) mechanism. AgOx seeds were identified as key species for triggering the octopus-like growth of MnO2 nanofibers and inserting Ag and Pt into the MnO2 crystalline framework. The interconnection and entanglement among nanofibers allowed the formation of mechanically strengthened hierarchical structures, leading to one of the most robust manganese-based aerogels to date. Impressively, the Pt/Ag-MnO2 aerogel also possessed promising selectivity and stability toward the electrocatalytic oxygen reduction reaction, with Pt showing a high mass activity of 1.6 A/(mgPt) at 0.9 V vs. RHE. Experimental characterization and theoretical calculation confirmed Pt single atoms to be located at substitutional lattice sites, which reduced the overall oxygen reduction barriers. Our approach suggests that SSS or other analogous nanofiber or nanowire growth strategies are powerful in controlling structural formation over the entire range of length scales while being applicable to fabricating single-atom catalysts.