The thermal stability and reduction kinetics of graphene oxide were studied by measuring the electrical resistivity of single-layer graphene films at various stages of reduction in high vacuum and by performing temperature programmed desorption (TPD) measurements of multilayer films in ultrahigh vacuum. The graphene oxide was exfoliated from the graphite oxide source material by slow-stirring in aqueous solution, which produces single-layer platelets with an average lateral size of ∼10 µm. From the TPD measurements, it was determined that the primary desorption products of the graphene oxide films for temperatures up to 300 °C are H 2 O, CO 2 , and CO, with only trace amounts of O 2 being detected. Resistivity measurements on individual single-layer graphene oxide platelets resulted in an activation energy of 37 ( 1 kcal/mol. The TPD measurements of multilayer films of graphene oxide platelets give an activation energy of 32 ( 4 kcal/mol.

The reaction of H 2 S with chromium, chromia, and Au/chromia films grown on a Pt͑111͒ crystal has been investigated using synchrotron-based high-resolution photoemission spectroscopy. At 300 K, H 2 S completely decomposes on polycrystalline chromium producing a chemisorbed layer of S that attenuates the Cr 3d valence features. No evidence was found for the formation of CrS x species. The dissociation of H 2 S on Cr 3 O 4 and Cr 2 O 3 films at room temperature produces a decrease of 0.3-0.8 eV in the work function of the surface and significant binding-energy shifts ͑0.2-0.6 eV͒ in the Cr 3 p core levels and Cr 3d features in the valence region. The rate of dissociation of H 2 S increases following the sequence: Cr 2 O 3 ϽCr 3 O 4 ϽCr. For chromium, the density of states near the Fermi level is large, and these states offer a better match in energy for electron acceptor or donor interactions with the frontier orbitals of H 2 S than the valence and conduction bands of the chromium oxides. This leads to a large dissociation probability for H 2 S on the metal, and a low dissociation probability for the molecule on the oxides. In the case of Cr 3 O 4 and Cr 2 O 3 , there is a correlation between the size of the band gap in the oxide and its reactivity toward H 2 S. The uptake of sulfur by the oxides significantly increases when they are ''promoted'' with gold. The Au/Cr 2 O 3 surfaces exhibit a unique electronic structure in the valence region and a larger ability to dissociate H 2 S than polycrystalline Au or pure Cr 2 O 3 . The results of ab initio SCF calculations for the adsorption of H 2 S on AuCr 4 O 6 and AuCr 10 O 15 clusters show a shift of electrons from the gold toward the oxide unit that enhances the strength of the Au(6s)↔H 2 S(5a 1 ,2b 1 ) bonding interactions and facilitates the decomposition of the molecule.

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