CO2 Hydrogenation Studies on Co and CoPt Bimetallic Nanoparticles Under Reaction Conditions Using TEM, XPS and NEXAFS

Cobalt and platinum-cobalt bimetallic alloy nanoparticles of uniform size distribution where prepared and supported on MCF-17 to produce a controlled and well-characterized model catalyst which was studied under reaction conditions during CO2 hydrogenation. Near edge X-ray absorption fine structure (NEXAFS) spectroscopy was used to elucidate the oxidation state of the catalyst under reaction conditions while the effect of reducing H-2 gas on the composition and structure of the bimetallic PtCo nanoparticles was measured using ambient pressure X-ray photoelectron spectroscopy (AP-XPS) and environmental transmission electron microscopy (ETEM). NEXAFS indicates that Pt aids the reduction of Co to its metallic state under relevant reaction conditions, while AP-XPS and ETEM indicate that Pt is enriched at the surface by exchange with subsurface layers which become Pt deficient-in agreement with the "Pt-like'' selectivity seen during catalytic testing of these materials.