Supported platinum\u2013zinc oxide core\u2013shell nanoparticle catalysts for methanol steam reforming

Platinum\u2013zinc oxide (Pt@ZnO) and palladium\u2013zinc oxide (Pd@ZnO) core\u2013shell nanoparticles were synthesized in solution using a method based on self-assembly and deposited onto a functionalized alumina (Si\u2013Al2O3) support. TEM investigations of the samples confirm the formation of core\u2013shell structures of approximately 6 nm of diameter following calcination to remove the ligands. In situ TEM and coulometric titration experiments suggest that Pt\u2013Zn 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\u2013Al2O3 system showed comparable activity and selectivity for CO2 as a conventional Pt/ZnO catalyst, providing further indication that Pt@ZnO forms a Pt\u2013Zn alloy upon reduction due to the intimate contact between the two materials. The Pd@ZnO/Si\u2013Al2O3 exhibited lower CO2 selectivities than Pt@ZnO/Si\u2013Al2O3