Supported platinum–zinc oxide core–shell nanoparticle catalysts for methanol steam reforming

Abstract

Platinum–zinc oxide (Pt@ZnO) and palladium–zinc oxide (Pd@ZnO) core–shell nanoparticles were synthesized in solution using a method based on self-assembly and deposited onto a functionalized alumina (Si–Al₂O₃) support. TEM investigations of the samples confirm the formation of core–shell structures of approximately 6 nm of diameter following calcination to remove the ligands. In situ TEM and coulometric titration experiments suggest that Pt–Zn alloys are formed upon reduction and that these are highly tunable in size. While methanol steam reforming (MSR) measurements on conventional Pt/Al₂O₃ and Pd/Al₂O₃ catalysts show poor CO₂ selectivities, a Pt (1 wt%)@ZnO (9 wt%)/Si–Al₂O₃ system showed comparable activity and selectivity for CO₂ as a conventional Pt/ZnO catalyst, providing further indication that Pt@ZnO forms a Pt–Zn alloy upon reduction due to the intimate contact between the two materials. The Pd@ZnO/Si–Al₂O₃ exhibited lower CO₂ selectivities than Pt@ZnO/Si–Al₂O₃.