On-paper synthesis of Au nanocatalysts from Au(III) complex ions for low-temperature CO oxidation

Au nanoparticles (AuNPs) were successfully synthesized in situ on a microstructured paper matrix composed of ceramic fibers as the main framework and ZnO whiskers as a preferential support for AuNPs. The paper-like ceramic fiber/ZnO whisker composites were prepared using a papermaking technique, then soaked in an aqueous solution of the Au(III) complex HAuCl₄. AuNPs with size <10 nm were spontaneously formed on the ZnO whiskers in the absence of reducing agents, possibly due to electron transfer from Zn(II) in ZnO whiskers to Au(III) species through Zn-O-Au bonds. As-prepared AuNPs@ZnO whisker-containing paper (AuNPs@ZnO paper) is much like ordinary paper products in being flexible, lightweight and easy to handle. AuNPs@ZnO paper demonstrated excellent catalytic performance in low-temperature CO oxidation. Complete conversion of CO to CO₂ was achieved at 20 °C, 140 K lower than the reaction temperature for conventional Au/ZnO catalyst powders. This facile technique has potentially broad wide applications in 'on-paper' synthesis of a diverse array of metal NPs. The metal NPs@ZnO paper composites with paper-like flexibility are able to fit various reactor configurations and are thus expected to be promising catalytic materials for improving the practical utility and catalytic performance of these systems, for a wide range of industrial chemical processes.