In-situ x-ray absorption experiments were performed on Co and CoPt NPs and fractions of Co oxidation states were mapped under the pressure from millitorr to one bar. Reducibility and oxidation states of Co in Co and CoPt NPs were compared. Pt has a substantial impact on the oxidation state and structure of Co. Co is much easier to reduce when alloying with Pt. Pt keeps Co in a more reduced state in the low pressure oxidizing conditions. When pressure is increased above 100 torr, Co and Co2+ fractions in Co and CoPt NPs tend to converge while Co has a much larger amount of Co3+ fraction in Co NPs. Specifically in the Co2+ oxidation state, Co2+ Td fraction drops for both Co and CoPt NPs at higher pressure while it is always higher for Co than CoPt NPs; Co2+ Oh fraction increases with increasing pressure for both Co and CoPt NPs while at high pressure it is higher for CoPt than Co NPs.

Evolution of oxidation state and structure of Co in Co and CoPt nanoparticles under the reaction environment

241st National Meeting (2011)

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