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Rational engineering of noble metal/transition metal bimetallic catalysts is considered as an effective way to constructing synergistic effect between adsorbed oxygen and hydroxyl for enhanced catalytic formaldehyde oxidation. Herein, we developed a Pt–Ni bimetallic catalysts loading on γ‐Al2O3 support for room‐temperature formaldehyde oxidation. Catalytic experiment results showed that the conversion rate was >97% with a >100 h stability. Several noble metals (Pd, Au, and Ag) were compared to identify the activity effect in formaldehyde oxidation. The activity and stability test in different atmospheres and in situ infrared test suggested that the PtNi/γ‐Al2O3 has the best activity and stability. At a meantime, the results also demonstrated that Pt sites motivate more surface adsorbed oxygen through activating ambient oxygen molecules, while the neighboring Ni atoms contribute to adsorbed hydroxyl, thereby offering sustainable activity. The high efficiency and stability of PtNi/γ‐Al2O3 catalysts for formaldehyde oxidation could be a promising candidate for air purification. [ABSTRACT FROM AUTHOR]

The paper is focused on evaluation of active centres and impact of adsorbed species on (10%Co+0.5%Pd) / Al2O3 catalyst system performance aiming selectivity optimization. Application of different sets of precursor pretreatment and reduction resulted in catalysts exhibiting high CO conversion or high methane selectivity. A sample of high selectivity was prepared by pretreatment in hydrogen and the performance was determined by lower amount of strongly adsorbed CO, strongly adsorbed carbonate species, and higher amount of reduced metal and bimetallic particles. A more active system was formed by pretreatment in air leading to larger amount of unreduced metal and CO-bridged species on the surface, stable coverage of hydroxyl groups on the support, and medium-strength sites for adsorption of carbonates. Ratios of hydrogen to carbon monoxide adsorption (H/CO) and of strongly to weakly adsorbed CO species appeared as important criteria for catalyst efficiency together with supported metal state, amount of unreduced ions, bimetallic particle formation, and alumina's ability to adsorb CO and CO2. [ABSTRACT FROM AUTHOR]

[Display omitted] • A theoretical database for predicting adsorbate-induced metal–metal bond scission. • Metal adatom formation is generally easier on (100) surfaces than (111) surfaces. • More open facets are required for adatom formation on intrinsically harder metals. • A new perspective for interpreting structure sensitivity in heterogeneous catalysis by metals. Recent surface science discoveries reveal that adsorbates may induce in situ sub-nanometer cluster formation on transition-metal surfaces. To elucidate the structure sensitivity behind this phenomenon, we performed density functional theory calculations to construct an adatom formation energy database for eight fcc metals and 26 adsorbates commonly involved in catalytic reactions. We show that the adatom formation on (100) surfaces is generally easier than that on (111) surfaces. Many adsorbate/metal pairs exist, mostly on Pd, Ni, Rh, Pt, and Ir, for which adsorbates might induce adatom formation under near-ambient conditions on the (100) facet, but not on (111), highlighting the role of more open facets in adatom formation on metals intrinsically harder than Ag, Au, and Cu. Our study offers a new perspective towards understanding structure sensitivity in heterogeneous thermal- and electro-catalytic systems such as methane steam reforming, Fischer-Tropsch synthesis, and ammonia decomposition. [ABSTRACT FROM AUTHOR]

Affection toward CO 2 adsorption-desorption processes under wet flue gas is significant. CO 2 adsorption-desorption properties of CeO 2 under dry and wet condition were measured. Unlike zeolite, CO 2 adsorption amounts for CeO 2 under dry and wet condition were almost equivalent. Compared to dry condition, CO 2 temperature-programmed desorption under wet condition showed larger desorption amount at low temperature below 463 K. This could result from formation of hydrogen carbonate species by enriching surface hydroxyl groups due to H 2 O. CO 2 and H 2 O desorption measurement showed that CO 2 and H 2 O desorption occurred at close temperature, which was explained by degradation of hydrogen carbonate species. [ABSTRACT FROM AUTHOR]

Standard equipment for electron spectroscopy empowers fingerprinting the adsorbed layer at atomic-molecular level. The resource results from the novel route for primary electron energy dissipation through a set of shake-off and shake-up electron transitions, each coupled with the threshold core level excitation. Experimental evidence for the route is based on regular fine structures in extended elastic electron spectra from the Pt(100) single crystal fitting the valence state structures of adsorbed species and substrate atoms as well as plasmon excitations; in total over 20 particular satellites have been detected in conventional experimental conditions. Theoretical justification of a route consists in the mechanism being a combination of well-known electron transitions. The phenomenon is considered as a fundamental regularity of electronsolid interaction disclosing the outer shell structure of near-surface atoms alike an Auger effect brings to light the inner shell structure. [ABSTRACT FROM AUTHOR]

Highlights: [•] IR spectra of CO adsorption are reported for both pressure and temperature as independent influences. [•] We outline the abnormal thermodynamic behavior of the so-called dual sites. [•] We evidence Silanol also interact and describe how SiOH impact CO adsorption. [•] Attributions of surface adsorbed species endorsed in the literature are called into question. [ABSTRACT FROM AUTHOR]

Highlights: [•] Steam reforming of toluene as a model compound of biomass tar, was investigated. [•] Ni/La0.7Sr0.3AlO3−δ catalyst showed higher activity and lower coke formation. [•] Surface adsorbate on steam reforming of toluene were observed using in situ IR. [•] The aromatic ring in toluene strongly adsorbed only on La0.7Sr0.3AlO3−δ . [•] The adsorbate reacted with steam at 673K on Ni/La0.7Sr0.3AlO3−δ . [ABSTRACT FROM AUTHOR]

Abstract: During the last decade, the laser desorption/ionization time-of-flight mass spectrometry (LDIToFMS) development has provided the opportunity to improve the understanding of the soot formation process. Combining LDIToFMS and shock-tube allows the study of adsorbed compounds on aged soot formed at constant and well defined temperature. The present work investigates effects of fuel structure (with 2-methyl-2-butene (2M2B)), fuel molecular composition (with thiophene, C4H4S) and the presence of oxygen (with toluene in pyrolysis and at an equivalence ratio of 18) on the composition of the adsorbed phase. The evolution, with the temperature behind reflected shock waves, of the soot induction delay time and the soot yield was also investigated from highly diluted mixtures in argon. LDIToFMS results show that PAHs were detected on soot. The mass range of PAHs is dependant on the fuel and on the temperature. The amount of species adsorbed on soot surface was found to be inversely proportional to the soot yield. A dominant sequence of benzenoid PAHs, with a 24-amu increment between peaks, is observed whatever the initial fuel or condition (temperature, presence of oxygen). A second sequence of five membered ring PAHs was also observed with a 12-amu increment between peaks of the benzenoid sequence. The signal intensity of this five membered ring PAHs sequence depends strongly on the temperature, the presence of oxygen and the structure the fuel. The presence of a sulphur atom in the structure of the initial fuel leads to the detection of small amounts of compounds adsorbed on soot which contain sulphur atom(s) and with a PAH-like structure. [Copyright &y& Elsevier]

Abstract: The reaction pathways for the photocatalytic oxidation of ethanol on the TiO2 surface at 30 °C were studied by in situ infrared (IR) spectroscopy. The coverage of ethanol and water was found to play a key role in how the reaction is initiated. The low ethanol coverage on the H2Oad-containing TiO2 surface produced adsorbed formate (HCOO− ad) as a primary intermediate; the high ethanol coverage on the H2Oad-deficient TiO2 surface produced adsorbed acetate (CH3COO− ad) as a major intermediate during the initial period (i.e., 2 min) of the photocatalytic oxidation. The adsorbed species and reaction products observed during in situ IR studies suggest the low-coverage ethanol reaction is initiated by •OH, whereas the high-coverage ethanol reaction is initiated by hole. The hole-initiating ethanol oxidation on the H2Oad-deficient TiO2 surface produced adsorbed acetic acid (CH3COOHad)/CH3COO− ad, and built up photogenerated electrons, giving a parallel increase in the IR intensity of CH3COO− ad and the IR background at 2000 cm−1 (i.e., a measure of photogenerated electrons). As the high-coverage ethanol reaction proceeded toward producing CO2/H2O, adsorbed H2O accumulated and the coverage of CH3CH2OHad/CH3CH2Oad decreased on the TiO2 surface, shifting the reaction from hole-initiating to •OH-initiating. [Copyright &y& Elsevier]

Abstract: Fourier Transform Infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to investigate the species adsorbed on TiO2 related to photocatalytic activity. Dichloroacetyl chloride (DCAC), which is generated during the photocatalytic oxidation of trichloroethylene (TCE), was the only species adsorbed on TiO2. Two types of DCAC were adsorbed – one at low concentration and another at high concentration. While adsorbed phosgene produced from DCAC was adsorbed strongly to TiO2, the adsorption of DCAC was relatively weak. The surface structures of the adsorbed DCAC at low and high concentrations on TiO2 were carboxylate compounds on single Ti–O bonds. The surface structures of carboxylate compounds were resolved to those of adsorbed phosgene, bidentate carbonate compounds, on the two Ti–O bonds during photocatalytic oxidation under UV irradiation. The adsorbed DCAC on TiO2 reduces the photooxidation rate of TCE, and the CHCl2 stretching vibration of adsorbed DCAC was considered to be the inactive species. The adsorbed DCAC and dichloroacetic acid (DCAA) were converted to adsorbed phosgene by photocatalytic oxidation on TiO2. [Copyright &y& Elsevier]

A class of adsorption mechanisms, namely those with a single electron-transfer step whose electronless species graphs are trees, is shown to have equivalent circuits containing only resistors and capacitors. Also for these mechanisms, a “topological” equivalent circuit can be chosen that is closely related to the graph of the reaction mechanism, so that the circuit may be written by inspection of this graph. [Copyright &y& Elsevier]

In situ absorption spectra of methylene blue (MB) adsorbed on an indium-tin-oxide electrode were observed by slab optical waveguide (SOWG) spectroscopy. The absorption spectrum of the MB obtained by the SOWG spectroscopy coincided with that by conventional spectroscopy for the solution phase, and the MB existed as dimer at 0 V vs. Ag/AgCl. Upon the electrode potential of cathodic condition, the absorption spectra gradually changed showing the appearance of the monomeric species as well as the highly aggregated species of MB. [Copyright &y& Elsevier]

Raman spectra of SOx adsorbed on γ-alumina and Pt/γ-alumina model catalysts have been obtained with a 244 nm Raman spectrometer. Strong peaks in the 980–1380 cm-1 region characteristic of adsorbed sulfates are clearly portrayed in the spectra, which contrast with fluorescence-dominated scans obtained using visible excitation. Broad bands are also observed in the 3500–3700 cm-1 O–H stretch region on the γ-alumina, which belong to weakly-bound physisorbed water and more strongly-bound surface hydroxyls. These features are monitored as the samples are heated up to 600°C in the presence of nitrogen. The sulfate peaks vary in position depending on whether or not the γ-alumina is loaded with platinum, hydrated, or dehydrated. Platinum appears to inhibit the physisorption of water and the formation of hydroxyls on the γ-alumina surface, as evidenced by the absence of O–H stretch vibrations on the Pt-loaded sample. Our spectral data demonstrate that UV Raman spectroscopy is a useful technique for analytical studies of adsorbed SOx on γ-alumina, and holds promise for future in situ investigations of other adsorbed species on catalytic substrates of automotive interest. [ABSTRACT FROM AUTHOR]