Stand-Alone Sponge-Shaped Mesoporous AuPt Alloy Nanosponges as Visible Photocatalyst for the Selective Reduction of CO₂ to CO

Bulk Au is chemically inert and a relatively poor catalyst while Pt is catalytically active. Nanostructured Au is an effective photocatalyst due to hot electrons generated by interband- and intraband damping of surface plasmons. A bimetallic, mesoporous AuPt catalyst with a large specific surface area is highly desirable due to the combination of hot carrier and catalytic promoter effects together with a large number of active reaction sites. Sponge-shaped AuPt alloy nanoparticles were grown by spontaneous thermal dewetting of ultrathin AuPtAg films followed by dealloying through removal of Ag. Selective etching of silver from AuPtAg alloy precursors formed a porous AuPt sheet-like nanostructure with mesopores with an average size of 3.72 nm. Under AM1.5G one sun illumination, the AuPt nanosponge acted as a stand-alone photocatalyst for CO 2 reduction by evolving CO at a rate of 1010 μmol g –1 h –1 with 100% selectivity. Scavenger experiments confirmed photogenerated electrons to be the driving force for chemical transformation as opposed to holes. AuPt nanosponge significantly outperformed bare Au nanosponge in both visible light-stimulated CO 2 photoreduction and photooxidative degradation of methylene blue dye, which is attributed to a non-negligible photoinduced electron transfer from Au to Pt followed by electron transfer to reactants.