Ag/AgBr/TiO2 was prepared by the deposition-precipitation method and was found to be a novel visible light driven photocatalyst. The catalyst showed high efficiency for the degradation of nonbiodegradable azodyes and the killing of Escherichia coli under visible light irradiation (lambda>420 nm). The catalyst activity was maintained effectively after successive cyclic experiments under UV or visible light irradiation without the destruction of AgBr. On the basis of the characterization of X-ray diffraction, X-ray photoelectron spectroscopy, and Auger electron spectroscopy, the surface Ag species mainly exist as Ag0 in the structure of all samples before and after reaction, and Ag0 species scavenged hVB+ and then trapped eCB- in the process of photocatalytic reaction, inhibiting the decomposition of AgBr. The studies of ESR and H2O2 formation revealed that *OH and O2*- were formed in visible light irradiated aqueous Ag/AgBr/TiO2 suspension, while there was no reactive oxygen species in the visible light irradiated Ag0/TiO2 system. The results indicate that AgBr is the main photoactive species for the destruction of azodyes and bacteria under visible light. In addition, the bactericidal efficiency and killing mechanism of Ag/AgBr/TiO2 under visible light irradiation are illustrated and discussed.

Ag/AgBr/TiO2 visible light photocatalyst for destruction of azodyes and bacteria

We report a combined X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and chronoamperometry (CA) study of formic acid electrooxidation on unsupported palladium nanoparticle catalysts in the particle size range from 9 to 40 nm. The CV and CA measurements show that the most active catalyst is made of the smallest (9 and 11 nm) Pd nanoparticles. Besides the high reactivity, XPS data show that such nanoparticles display the highest core-level binding energy (BE) shift and the highest valence band (VB) center downshift with respect to the Fermi level. We believe therefore that we found a correlation between formic acid oxidation current and BE and VB center shifts, which, in turn, can directly be related to the electronic structure of palladium nanoparticles of different particle sizes. Clearly, such a trend using unsupported catalysts has never been reported. According to the density functional theory of heterogeneous catalysis, and mechanistic considerations, the observed shifts are caused by...

Size effects in electronic and catalytic properties of unsupported palladium nanoparticles in electrooxidation of formic acid.

The interaction of H2O with a TiO2(110) surface

A study of a number of mixed transition metal oxide spinels using X-ray photoelectron spectroscopy

Electrodeposited manganese oxide films (MnOx) are promising stable oxygen evolution catalysts. They are able to catalyze the oxygen evolution reaction in acidic solutions but with only modest activity when prepared by constant anodic potential deposition. We now show that the performance of these catalysts is improved when they are “activated” by potential cycling protocols, as measured by Tafel analysis (where lower slope is better): upon activation the Tafel slope decreases from ∼120 to ∼70 mV/decade in neutral conditions and from ∼650 to ∼90 mV/decade in acidic solutions. Electrochemical, spectroscopic, and structural methods were employed to study the activation process and support a mechanism where the original birnessite-like MnOx (δ-MnO2) undergoes a phase change, induced by comproportionation with cathodically generated Mn(OH)2, to a hausmannite-like intermediate (α-Mn3O4). Subsequent anodic conditioning from voltage cycling or water oxidation produces a disordered birnessite-like phase, which is ...

Nature of Activated Manganese Oxide for Oxygen Evolution

Atomic standards of binding energies are presented for the calibration of X-ray photoelectron spectrometers. The binding energies are measured using a VG Scientific ESCA 3 Mk II for which the photoelectron peak positions can be established with a measurement precision standard deviation of 5 meV. The absolute calibration of the voltage scale is established with an accuracy of 11 ppm over the binding energy range 0–1250 eV, using a measurement chain traceable to the NPL primary voltage standards. The zero of energy is set to ±11 meV on the differential of the Ni Fermi edge using Mg Kα12 radiation and absolute binding energies, for the Cu 2p3/2, Cu L3MM, Cu 3p, Ag 3d5/2, Ag M4NN and Au 4f7/2 peaks, are established with errors of 0.01 to 0.02 eV. An analysis is made of literature calibrations to assess their zero setting and voltage scaling errors. Preliminary tests have been made to show that the calibrations may be reproduced on instruments outside NPL using a simple work procedure.

AES: Energy calibration of electron spectrometers. I—an absolute, traceable energy calibration and the provision of atomic reference line energies

XPS: Energy calibration of electron spectrometers. 2—Results of an interlaboratory comparison

The ASTM E-42 committee round robin on XPS measurements found, in a simple survey, that the intensity-energy response of electron spectrometers was unacceptably unreliable. In this paper new, high accuracy, reference procedures are developed to define the relative intensity-energy response function of spectrometers, for the constant ΔE and ΔE/E modes, for analysts to calibrate their own instruments. Two procedures are developed, one involving the measurement of peak areas, for Cu, Ag and Au, carefully specified to reduce the effects of measurement noise, and the second, for use on well-designed spectrometers, through the measurement of the spectrum background. The measurements on Cu, Ag and Au reference foils show that intensity ratios are reproducible to within 2% standard deviation and, from preliminary tests, that the ratio of the response functions of a VG Scientific ESCALAB I and the NPL ESCA 3 Mk II is proportional to E0.094, except for the low pass energy of 20 eV in the ESCALAB I where the proportionality changes to E−0.156. Similarly the ratio of the functions for a Perkin-Elmer PHI 550 and the VG Scientific ESCA 3 Mk II is proportional to E−0.244 over the normal XPS measurement range to an accuracy of 2%.

Quantitative XPS: The calibration of spectrometer intensity—energy response functions. 1—The establishment of reference procedures and instrument behaviour

Deux methodes d'evaluation de la fonction reponse sont testees: la mesure de la surface des pics et les donnees de fond des spectres de feuilles de Cu, Ag et Au

Quantitative XPS: The calibration of spectrometer intensity—energy response functions. 2—Results of interlaboratory measurements for commercial instruments

M. T. Anthony

Papers

AES: Energy calibration of electron spectrometers. I—an absolute, traceable energy calibration and the provision of atomic reference line energies

XPS: Energy calibration of electron spectrometers. 2—Results of an interlaboratory comparison

Quantitative XPS: The calibration of spectrometer intensity—energy response functions. 1—The establishment of reference procedures and instrument behaviour

Quantitative XPS: The calibration of spectrometer intensity—energy response functions. 2—Results of interlaboratory measurements for commercial instruments

Intensity and energy calibration in AES: The effect of analyser modulation