With its high flux and wide angular range coverage, the Nanoscale Ordered Materials Diffractometer at the Spallation Neutron Source allows for in situ neutron total scattering studies of materials undergoing chemical processes and reactions with temporal resolution of minutes or seconds. At the same time, pair distribution function studies (PDF) have proven effective in characterizing both bulk and surface structures in nano and porous materials. By combining these capabilities with a recently commissioned high-precision gas flow cell sample environment, we are able to study both the average and local structure of catalytic materials in real-time and at elevated temperatures. We will present results targeting the structure and dynamics of gas-solid interfaces driving two materials processes: (1) the selective adsorption of N2 in Zeolite-X under 1 atm flow at room temperature, demonstrating sensitivity to the active adsorption site and framework response of the host; and (2) the oxidation and reduction behaviors of nanocubes and nanorods of ceria at elevated temperatures, specifically following the nature of oxygen vacancies and catalytic performance in selective hydrogenation reactions. Efforts to isolate the distinct structural signatures of interfacial species are enhanced through the use of pulsed-probe isotope contrasted variation techniques, utilizing alternating 14N2/15N2 or D2/H2 gas flows, respectively. Opportunities for further in operando investigation of industrially relevant gas sorption, separation, and catalysis processes will be discussed.

Probing solid-gas interfaces in situ with isotope contrasted neutron total scattering

256th National Meeting (2018)

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