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Density functional theory study of direct synthesis of H2O2 from H2 and O2 on Pd(111), Pd(100), and Pd(110) surfaces

Abstract The direct synthesis of hydrogen peroxide (H2O2) from hydrogen (H2) and oxygen (O2) on Pd(111), Pd(100), and Pd(110) surfaces was investigated using periodic density functional theory (DFT) calculations. Several elementary steps making up this reaction were postulated and calculated. The Pd(111) surface shows the highest catalytic selectivity for H2O2 among the three surfaces. Open surfaces such as Pd(100) and Pd(110) are not favorable for this reaction because O–O-containing species on these surfaces dissociate easily. The O–O bond energy and the binding energy of O–O-containing surface species are responsible for catalytic selectivity. The higher binding energy of O–O-containing surface species is not favorable for the direct synthesis of H2O2 because the higher binding energy results in lower dissociation barriers.

Dispersing Pd nanoparticles on N-doped TiO2: a highly selective catalyst for H2O2 synthesis

The selectivity of H2O2 synthesis directly from H2 and O2 over Pd/TiO2 catalysts was found to be improved greatly if TiO2 was doped by nitrogen before dispersing the Pd nanoparticles. The structure of Pd catalysts supported on different N-doped TiO2 was characterized with the combination of XRD, TEM, in situ CO-DRIFTS and XPS results. The average size of Pd particles (dPd: ∼2.2 nm) showed no discernible differences, while the chemical states of Pd atoms changed significantly over Pd/N–TiO2 treated in different atmospheres. The reaction rate decreases in the order of H2 > O2 > N2, corresponding to the same increasing order of Pd2+/Pd. Likely, dispersing Pd nanoparticles on N–TiO2 should be an effective way to tune the interface structure of Pd/PdO, which acts as the active site for H2O2 synthesis.

CHAPTER 8:Advances in Catalytic Reactions by Gold-based Catalysts Through the Radical Chain Mechanism

Unlike the published literature, the chapter focuses on recent developments in our understanding of the radicals involved catalytic reactions on heterogeneous gold-based catalysts. This chapter is composed of four parts: (1) selective oxidation of alkanes; (2) selective oxidation of alkenes; (3) selective oxidation of alcohols and aldehydes; and (4) Fenton-like reaction and photocatalytic oxidation. The role of gold in the decomposition of hydrogen peroxide is analysed and the mechanism for the production of hydroxyl radicals (•OH) is envisaged.