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    • "Actually, PdO has been utilized as a catalyst in the research field of catalysis. For example, Weaver's group[16]investigated the molecular adsorption and dissociation of n-butane on a PdO (1 0 1) thin film using temperature-programmed reaction spectroscopy (TPRS) experiments and density functional theory (DFT) calculations , and found that the formation of relatively strongly-bound complexes on PdO (1 0 1) serves to electronically activate CÀ ÀH bonds in addition to prolonging the surface lifetime of these reactive precursors. Lu et al.[17]studied the influence of the synthesis method on the structures of Pd-substituted perovskite catalysts for methane oxidation, and reported that the exposure of PdO on the perovskite oxide surface was crucial for the catalytic activity. "
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    ABSTRACT: Palladium (Pd) composite nanoparticles (NPs) supported on multi-walled carbon nanotubes (MWCNTs) (denoted as Pd/MWCNTs) are fabricated by a very simple process of hydrothermal reaction (HR) using the technical grade PdO as the precursor. With a HR period of 3 h, the Pd NPs with an average size of ∼5.0 nm are found to be quite uniformly dispersed on the surface of MWCNTs. The electrocatalytic activity towards ethanol oxidation reaction (EOR) for the synthesized catalysts is probed by using cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). The 3-h prepared catalyst has demonstrated 6.7 times better EOR activity than 5-h prepared sample (159.7 mA mg−1 vs. 23.8 mA mg−1) at an applied potential of −0.24 V (vs. SCE) in the CA test. The excellent electrocatalytic activity of the 3-h Pd/MWCNTs catalyst toward EOR is mainly ascribed to its easier hydrogen evolution, lower electrode potential and the existence of PdO as compared to other catalysts prepared.
    Full-text · Article · Jul 2015 · Electrochimica Acta
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    ABSTRACT: The kinetics of catalytic oxidation of methane (1–3% in air) over a palladium oxide (PdO) surface was investigated by wire microcalorimetry at atmospheric pressure and over the temperature range from 560 to 800 K. Wire surface structures and compositions were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and atom force microscopy. It was found that a porous PdO layer with a constant thickness of 1–2 μm was formed on the Pd wire after it was heat treated in nitrogen followed by air at elevated temperatures. Under the condition of the experiment, the reaction was found to be in the pseudo-first-order regime with respect to the methane concentration. The apparent rate constant of methane oxidation on PdO was determined to be kapp(cm/s) = (3.2 ± 0.8) × 104e–(62.8±1.6)(kJ/mol)/RT for 600 < T < 740 K. Experimental data were analyzed using a gas–surface reaction model proposed previously. Analysis shows that the overall catalytic oxidation rate is governed by equilibrium adsorption/desorption of molecular oxygen, which determines the density of surface palladium sites and dissociative adsorption of methane on these sites. The equilibrium constant of O2 adsorption and desorption was estimated from literature values of desorption energy and molecular parameters of adsorbed oxygen atoms. The rate coefficient of methane dissociative adsorption was estimated to be k16(cm/s) = (7.7 ± 1.6) × 104e–(59.9±1.2)(kJ/mol)/RT, derived from the equilibrium constant of oxygen adsorption over the same temperature range.
    Full-text · Article · Sep 2013 · The Journal of Physical Chemistry C
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    ABSTRACT: Rapid advances in the nanosciences and colloidal chemistry have generated new opportunities in the fields of physical and chemical science, including tuning the size, shape, and composition of noble metals at nanoscale, which have revealed many interesting properties. Studies identifying molecular factors that affect catalytic activity provide the means to control catalytic activity, a significant achievement in catalysis. Several molecular factors, including structural and electronic effects, metal-support interactions, and the presence of a surface oxide layer, have been reported as candidates for improving catalytic activity. Among these factors, the oxide layer on the metal surface is considered to play an important role in determining catalytic activity and there are a growing number of studies in this area. Understanding the chemical reactivity of a metal oxide is a rather complicated issue, requiring significant research to date. We outline here recent experimental work on the role of surface oxide on metal nanoparticles (NPs) that determines the catalytic activity of heterogeneous catalysis, including the effect of oxidation states of nanoparticles on the catalytic activity for model catalysts of single crystals and nanoparticles, with several examples, including Pt, Rh, Ru, and Pd. © 2014 Springer Science+Business Media New York. All rights are reserved.
    Full-text · Chapter · Jan 2014
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