@article{reifsnyder_otten_lamb_1998, title={Nucleation and growth of Pd clusters in mordenite}, volume={39}, ISSN={["0920-5861"]}, DOI={10.1016/S0920-5861(97)00121-1}, abstractNote={The nucleation and growth of Pd clusters in mordenite were investigated using in situ extended X-ray absorption fine structure (EXAFS) spectroscopy and Fourier transform infrared (FTIR) spectroscopy of adsorbed CO. Calcination of [Pd(NH3)4]2+-exchanged mordenite at 350°C in O2 results in decomposition of the amine complex and formation of square-planar Pd2+ oxo species within the mordenite pores. Reduction of these species at 150°C in H2 yields Pd clusters with an average nuclearity of 3. On an average two 2.22 Å Pd–O bonds are associated with each Pd3 cluster; we infer that this interaction serves to anchor the clusters within the pores. After reduction at 150°C, the FTIR spectrum of irreversibly adsorbed CO is indicative of a mixture of Pd+, Pdδ+, and Pd0 carbonyl species. Reduction at 350°C produces larger intrazeolitic Pd clusters (average nuclearity of 6) that exhibit only a weak interaction with the mordenite, as evidenced by their facile aggregation in the presence of CO at 30°C. Reduction at 450°C yields large 20 Å Pd clusters that we infer are located on external mordenite surfaces or locally disrupt the intracrystalline structure.}, number={4}, journal={CATALYSIS TODAY}, author={Reifsnyder, SN and Otten, MM and Lamb, HH}, year={1998}, month={Mar}, pages={317–328} }
 @article{reifsnyder_otten_sayers_lamb_1997, title={Hydrogen chemisorption on silica-supported Pt clusters: In situ X-ray absorption spectroscopy}, volume={101}, ISSN={["1089-5647"]}, DOI={10.1021/jp970244e}, abstractNote={Hydrogen chemisorption on small silica-supported Pt clusters was investigated using in situ extended X-ray absorption fine structure (EXAFS) spectroscopy and X-ray absorption near-edge structure (XANES) spectroscopy. The clusters were found to exhibit a bulklike Pt first nearest neighbor (NN) distance (2.76 A) and low disorder while covered by chemisorbed hydrogen. In contrast, bare Pt clusters produced by heating in vacuo at 300 °C are characterized by a contracted Pt NN distance (2.66 A) and greater disorder. These effects are reversed by re-exposure of the bare Pt clusters to H2 at 25 °C. The metal−support interface is characterized by a short Pt−O distance, irrespective of the presence of chemisorbed hydrogen. An apparent L3 edge shift of 0.8 eV relative to bulk Pt is observed for the hydrogen-covered clusters. This shift is attributed to a decrease in the Pt L3 edge resonance (white line) intensity, as no corresponding shift is observed at the L2 edge. A hydrogen-related L2,3 XANES feature at 9 eV ap...}, number={25}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Reifsnyder, SN and Otten, MM and Sayers, DE and Lamb, HH}, year={1997}, month={Jun}, pages={4972–4977} }