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Here, the concept of preferential leaching of cerium oxide on ternary Pt–C–CeO2 compound is demonstrated in order to develop a cost‐effective catalyst for the cathode in proton exchange membrane fuel cells. The Pt–C–CeO2 thin film catalyst is prepared by simultaneous magnetron co‐sputtering of Pt, C, and CeO2. The morphology, structure, and composition of the Pt–C–CeO2 layer are characterized by transmission electron microscopy, scanning electron microscopy, energy dispersive X‐ray spectroscopy, X‐ray photoelectron spectroscopy, and X‐ray diffraction. Both half‐cell and single‐cell tests are performed to determine its activity and durability. During an activation electrochemical cycling procedure, CeO2 is leached from the compound, leaving behind a porous Pt–C matrix which exhibits almost 3 times higher electrochemically active surface area in comparison with pure Pt with identical loading before and even after accelerated degradation tests in the half‐cell. When used as the cathode in a single‐cell membrane electrode assembly, decomposed Pt–C–CeO2 also shows greater power density than pure Pt. [ABSTRACT FROM AUTHOR]

Tin oxide is a material that attracts attention due to variety of technological applications. The main parameters that influence its properties are morphology, crystalline structure and stoichiometry. Researchers try to develop nanostructured thin films with tunable parameters that would conform its technological applications. Herein, we report on the preparation and characterization of highly porous SnO 2 and Pd-doped SnO 2 thin films. These films were deposited in the form of nanorods with controllable geometry. Such morphology was achieved by utilizing glancing angle deposition (GLAD) with assisted magnetron sputtering. This arrangement allowed preparation of slanted pillars, zig-zag structure, vertically standing posts, spiral posts and "bush"-like structures. We calculated that slanted pillars feature the highest surface area among the listed. Then, sets of slanted pillars were deposited and studied in more details. Tin oxide films were thoroughly characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and synchrotron radiation photoelectron spectroscopy (SRPES). The influence of substrate annealing during the deposition and Pd doping on the morphology, crystalline structure and stoichiometry of the films are discussed. GLAD with assisted magnetron sputtering allowed us to deposit broad range of SnO 2 nanostructures while annealing of the substrate during deposition affected the films crystallinity. Also, we found out that doping of the SnO 2 films with Pd leads to alloy phase formation. These findings can be applied in variety of applications including gas sensing, catalysis, optics and electronics. Image 1 • Highly porous SnO 2 and Pd-SnO 2 films with variable geometry were deposited using GLAD. • Surface area of the films was analyzed by image processing and computer modeling. • Annealing during deposition resulted in high crystallinity of the films while maintaining a high surface area. • XPS, SRPES and TEM measurements showed that Sn4+ is the main oxidation state. • Formation of Sn-Pd alloy was confirmed by XPS and TEM in case of Pd-doped SnO 2. [ABSTRACT FROM AUTHOR]

• Overlapping the XPS Pt 4f and Cu 3p spectra of Pt-Cu alloys complicates its analysis. • XPS Cu 3p spectra were examined for all oxidation states of copper (Cu0, Cu+, Cu2+). • The Cu 3p spectra were then used for the precise fitting of Pt-Cu XPS Pt 4f spectra. The progress in the design of a perspective alloy catalyst relies on correct interpretation of its photoelectron spectra. Particularly, X-ray photoelectron spectroscopic (XPS) analysis of platinum-copper alloys represents a serious challenge for both qualitative and quantitative analyses due to the complexity of the Pt 4f spectra arising from its overlapping with the Cu 3p region. Studies regarding XPS investigation of Pt-Cu alloys often ignore the Cu 3p contribution while fitting Pt 4f spectra, which leads to partially incorrect interpretation of measured XPS data. This is most noticeable for alloys containing more than 50 % of platinum where the low-intensity Cu 3p core levels can be hidden under a more intense contribution of Pt 4f. In this work, we present the correct way of processing photoemission spectra of such systems. First, we thoroughly examine the XPS Cu 3p spectra of pure copper surfaces of different oxidation states, namely Cu°, Cu+, and Cu2+. Then, the obtained results are applied for the fitting of Pt 4f spectra of both metallic and oxidized Pt-Cu systems. The precise curve-fitting and data analysis procedure showcased in this study can be utilized to eliminate uncertainties in the analysis of Pt-Cu photoemission spectra. [ABSTRACT FROM AUTHOR]

In this work, we investigate ethanol (EtOH)-sensing mechanisms of a ZnO nanorod (NRs)-based chemiresistor using a near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS). First, the ZnO NRs-based sensor was constructed, showing good performance on interaction with 100 ppm of EtOH in the ambient air at 327 °C. Then, the same ZnO NRs film was investigated by NAP-XPS in the presence of 1 mbar oxygen, simulating the ambient air atmosphere and O2/EtOH mixture at the same temperature. The partial pressure of EtOH was 0.1 mbar, which corresponded to the partial pressure of 100 ppm of analytes in the ambient air. To better understand the EtOH-sensing mechanism, the NAP-XPS spectra were also studied on exposure to O2/EtOH/H2O and O2/MeCHO (MeCHO = acetaldehyde) mixtures. Our results revealed that the reaction of EtOH with chemisorbed oxygen on the surface of ZnO NRs follows the acetaldehyde pathway. It was also demonstrated that, during the sensing process, the surface becomes contaminated by different products of MeCHO decomposition, which decreases dc-sensor performance. However, the ac performance does not seem to be affected by this phenomenon. [ABSTRACT FROM AUTHOR]

• Pt x Ni 100-x catalysts were deposited by magnetron co-sputtering from two targets. • Composition, morphology and thickness was adjusted by tuning deposition parameters. • Pt x Ni 100-x alloys demonstrated promising platinum utilization in PEMFCs. In this study, Pt x Ni 100-x (0 ≤ x ≤ 100) alloy catalysts were prepared using magnetron co-sputtering in order to reveal the correlation between their composition and catalytic properties as a cathode in proton exchange membrane fuel cells (PEMFCs). Fine power adjustment on magnetrons allowed to deposit alloys with precise composition and at the same time with identical thickness of 10 nm and similar morphologies. The powerful surface characterization techniques such as atomic force microscopy (AFM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray reflectivity (XRR) and X-ray photoelectron spectroscopy (XPS) were applied to thoroughly investigate the catalytic layers. The desired composition of the films was confirmed by EDX and XRD results. All deposited layers showed similar morphologies with vertical and horizontal roughness of ~0.35 nm and ~6 nm, respectively. XRD confirmed the alloy nature of the films with one crystalline phase of the fcc PtNi. The Pt x Ni 100-x alloys showed significant enhancement of specific power (SP) comparing to the pure Pt in PEMFC. Particularly, the Pt 25 Ni 75 sample exhibited the highest SP of 24 kW/g(Pt). This catalyst showed a 2- and almost 10-fold improvement in SP with respect to the Pt film and commercial nanopowder Pt catalyst, respectively. [ABSTRACT FROM AUTHOR]

Electrodeposition is widely used for industrial applications to deposit thin films, coatings, and adhesion layers. Herein, CeO 2 thin films were deposited on a highly oriented pyrolytic graphite (HOPG) substrate by cathodic electrodeposition. The influence of the deposition parameters on the yield and on the film morphology is studied and discussed. Morphology and composition of the electrodeposited films were characterized by in-situ atomic force microscopy (AFM), scanning electron microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). By AFM we show that the thickness of CeO 2 films can be controlled via the Ce 3+ concentration in solution and the deposition time. After exposing the films to ambient air, cracking structures are formed, which were analyzed by AFM in detail. The chemical composition of the deposits was analyzed by XPS indicating the formation of nearly stoichiometric CeO 2 . [ABSTRACT FROM AUTHOR]

Platinum-based bimetallic alloys possess unique activities exceeding those of pure platinum. Nevertheless, as complex multi-component systems, they suffer from surface structural reorganization under operating conditions, strongly affecting their lifetime performance. This work reports an in situ electrochemical and spectroscopic study of surface compositional changes in a PtNi catalyst during repetitive oxidation/reduction cycles, simulating inherent working conditions for numerous redox reactions. Using cyclic voltammetry and near-ambient pressure X-ray photoelectron spectroscopy, quantitative surface characterization under realistic electrified liquid and gaseous environments are obtained and correlated. We show that regardless of the operating environment, PtNi undergoes a significant and irreversible change in compositional profile reflected in surface nickel enrichment and consequent catalyst deactivation, exemplary confirmed using a methanol electrooxidation reaction. [Display omitted] • Surface compositional dynamics in PtNi alloy under reaction conditions were studied in situ. • The catalyst behaviour under electrochemical and gaseous environments are compared and correlated. • The series of redox cycles result in gradual nickel enrichment on the surface. • Changes in surface composition strongly influence PtNi activity. [ABSTRACT FROM AUTHOR]

• High (≥65%) 1,3-butadiene selectivity is achieved over Cu/La(-Zr)-Si catalysts. • Modification with La increases Cu/Zr-Si activity in aqueous ethanol conversion. • The effect is explained by formation of base sites being tolerant to H 2 O action. • NAP-XPS is used to elucidate active catalyst components under reaction conditions. This paper presents the results of an investigation of three (Cu/La-Si and Cu/Zr-Si) and four (Cu/La-Zr-Si) component oxide systems in aqueous ethanol conversion into 1,3-butadiene, with special accent to the effect of lanthanum in the catalyst composition. The catalysts were characterized by HRTEM, SEM, DR UV−vis, in situ near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS), FTIR with pyridine, and TPD-CO 2. The high (≥65%) 1,3-butadiene selectivity is achieved during the conversion of both rectified and aqueous ethanol over the studied catalysts. Catalyst activity of the four-component oxide systems depends on an introduction order of the components, which determines acid-base characteristics of the surface. A modification of the Cu/Zr-Si catalyst with lanthanum increases their activity in aqueous ethanol conversion into 1,3-butadiene. The positive effect of lanthanum addition into Cu/Zr-Si catalyst can be explained by the formation of lanthanum-containing base sites like [La–Ö–Si] and [La–Ö–H] being tolerant to the action of water. The differences in the interaction of reaction intermediates with surface Zr- and La-containing sites are found out by C 1 s NAP-XPS measurements, and the effect of H 2 O on adsorption of carbon coke, ethoxy species and acetaldehyde over the catalyst surface is shown. [Display omitted] [ABSTRACT FROM AUTHOR]

• Polycrystalline cerium oxide was prepared by a magnetron sputtering method. • Dextran and glucose adsorbed on cerium oxide via hydroxyl groups. • There is a mutual charge transfer between dextran and Ce ions. • Dextran adsorbed on cerium oxide was stable below 100 °C. This study used non-reactive magnetron sputtered polycrystalline cerium oxide thin films as model substrates to mimic the surface morphology of cerium oxide nanoparticles. We investigated the interaction between dextran and polycrystalline cerium oxide surfaces by atomic force microscopy, X-ray photoelectron spectroscopy, and reflection-absorption infrared spectroscopy. A simplified sample preparation method probing solid-liquid interface was set up by conducting aqueous adsorption procedures in an argon-filled glove bag connected to an ultra-high vacuum chamber. We found that the adsorption of dextran from aqueous solution onto the polycrystalline cerium oxide surface leads to a mutual charge transfer between dextran and cerium ions, creating a surface accumulation of Ce3+. In the aqueous environment, dextran hydroxyl groups adsorbs on the polycrystalline cerium oxide surface competitively with the dissociated hydroxyl groups from water. By investigating glucose adsorbed onto polycrystalline ceria prepared by physical vapor deposition, we further confirmed the role of hydroxyl groups from polysaccharide during interaction with ceria. Thermal annealing of the dextran adsorbed polycrystalline cerium oxide surface results in desorption of weakly bonded dextran below 100 °C and decomposition of dextran above 100 °C. [ABSTRACT FROM AUTHOR]