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

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.