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Understanding how reaction conditions affect metal-support interactions in catalytic materials is one of the most challenging tasks in heterogeneous catalysis research. Metal nanoparticles and their supports often undergo changes in structure and oxidation state when exposed to reactants, hindering a straightforward understanding of the structure-activity relations using only ex situ or ultrahigh vacuum techniques. Overcoming these limitations, we explored the metal-support interaction between gold nanoparticles and ceria supports in ultrahigh vacuum and after exposure to CO. A combination of in situ methods (on powder and model Au/CeO2 samples) and theoretical calculations was applied to investigate the gold/ceria interface and its reactivity toward CO exposure. X-ray photoelectron spectroscopy measurements rationalized by first-principles calculations reveal a distinctly inhomogeneous charge distribution, with Au+ atoms in contact with the ceria substrate and neutral Au0 atoms at the surface of the Au nanoparticles. Exposure to CO partially reduces the ceria substrate, leading to electron transfer to the supported Au nanoparticles. Transferred electrons can delocalize among the neutral Au atoms of the particle or contribute to forming inert Auδ− atoms near oxygen vacancies at the ceria surface. This charge redistribution is consistent with the evolution of the vibrational frequencies of CO adsorbed on Au particles obtained using diffuse reflectance infrared Fourier transform spectroscopy.

Ru evaporation from the surface of a Ru/CeO2 catalyst is demonstrated.

Stabilization of cathode catalysts in hydrogen-fueled proton-exchange membrane fuel cells (PEMFCs) is paramount to their widespread commercialization. Targeting that aim, Pt-Au alloy catalysts with various compositions (Pt

Platinum-based bimetallic alloys have been largely investigated during the last few years as a valid alternative to bare Pt cathode catalysts for proton-exchange membrane fuel cells (PEMFCs) to improve their cost-efficiency. Nonetheless, Pt bimetallic alloys are characterized by a reduced stability, which is poorly understood at a fundamental level. It is thus essential to describe the entire chain of interconnected degradation mechanisms to formulate a comprehensive model of catalyst degradation that will help interpret bimetallic alloy behavior in real complex fuel cell systems. By combining in situ inductively coupled plasma mass spectroscopy, in situ grazing-incidence small-angle X-ray scattering, and ex situ scanning electron microscopy, we have studied the morphological evolution of PtXNi100–X model catalysts with different Ni contents (ranging from 0 to 75%) undergoing potentiodynamic cycling to two different upper potentials mimicking the different operational conditions of a PEMFC: 1.0 and 1.3 VRHE. Data analysis allowed us to develop a methodology to distinguish the influence of Ni dissolution, particle coalescence, and Ostwald ripening on particle size distribution and interparticle distance and to realize time-dependent interplay maps to highlight the timeframe in which the aforementioned phenomena are prevailing or coexisting. Results show that Ni dissolution is the only phenomenon inducing morphological evolution when the lower upper potential is chosen. On the contrary, at 1.3 VRHE, Ni dissolution is rapidly overcome by particle coalescence at first and by Ostwald ripening in the later stages of the investigated time range. The onset of every phenomenon was found to occur earlier in time for larger values of Ni concentrations.

Single-atom catalysts represent an essential and ever-growing family of heterogeneous catalysts. Recent studies indicate that besides the valuable catalytic properties provided by single-atom active sites, the presence of single-atom sites on the catalyst substrates may significantly influence the population of supported metal nanoparticles coexisting with metal single atoms. Treatment of ceria-based single-atom catalysts in oxidizing or reducing atmospheres was proven to provide precise experimental control of the size of the supported Pt nanoparticles, and, correspondingly, control of catalyst activity and stability. Based on dedicated surface science experiments, ab-initio calculations and kinetic Monte-Carlo simulations we demonstrate that the morphology of Pt nanoparticle population on ceria surface is a result of a competition for Pt atoms between Pt single-atom sites and Pt nanoparticles. In oxidizing atmosphere, Pt single-atom sites provide strong bonding to single Pt atoms and Pt nanoparticles shrink. In reducing atmosphere, Pt single atom sites are depopulated and Pt nanoparticles grow. We formulate a generic model of Pt redispersion and coarsening on ceria substrates. Our model provides a unified atomic-level explanation for a variety of metal nanoparticle dynamic processes observed in single-atom catalysts under stationary or alternating oxidizing/reducing atmospheres, and allows to classify the conditions when nanoparticle ensembles on single-atom catalysts substrates can be stabilized against Ostwald ripening.

The electrochemical activity of modern Fe-N-C electrocatalysts in alkaline media is on par with that of platinum. For successful application in fuel cells (FCs), however, also high durability and longevity must be demonstrated. Currently, a limited understanding of degradation pathways, especially under operando conditions, hinders the design and synthesis of simultaneously active and stable Fe-N-C electrocatalysts. In this work, using a gas diffusion electrode half-cell coupled with inductively coupled plasma mass spectrometry setup, Fe dissolution is studied under conditions close to those in FCs, that is, with a porous catalyst layer (CL) and at current densities up to -125 mA·cm

An investigation of hydrotalcite-derived ternary Mg-Al-Ce oxides as catalysts for vapour phase condensation of ethanol to 1-butanol in a flow reactor under atmospheric pressure was carried out. The Mg-Al-Ce oxide systems with Mg/(Al + Ce) ratio from 1 to 4 were synthesized and characterized by XRD, SEM, NMR, and XPS. The study of acid-base characteristics of the systems with different Mg/(Al+Ce) ratio by NH3/CO2 quasi-equilibrium thermal desorption techniques shows that the ratio of the catalyst oxide components (Mg, Al, Ce) can provide acid/base capacity ratio close to 3 for the effectivity of the target process. The highest selectivity 68% is reached over Mg-Al-Ce oxide catalyst with the ratio of Mg/(Al+Ce) = 2.

Currently, platinum is the most widely used catalyst for low temperature proton exchange membrane fuel cells (PEMFC). However, the kinetics at the cathode are slow, and the price of platinum is high. To improve oxygen reduction reaction (ORR) kinetics at the cathode, platinum can be alloyed with rare earth elements, such as yttrium. We report that Pt3Y has the potential to be over 2 times more active for the ORR compared with Pt inside a real fuel cell. We present detailed photoemission analysis into the nature of the sputtered catalyst surface, using synchrotron radiation photoelectron spectroscopy (SRPES) to examine if surface adsorbates or impurities are present and can be removed. Pretreatment removes most of the yttrium oxide in the surface leaving behind a Pt overlayer which is only a few monolayers thick. Evidence of a substochiometric oxide peak in the Y 3d core level is presented, this oxide extends into the surface even after Ar+ sputter cleaning in-situ. This information will aid the development of new highly active nanocatalysts for employment in real fuel cell electrodes.

Simultaneous plasma etching of a proton-exchange membrane (PEM) and deposition of a cerium oxide layer during reactive magnetron sputtering leads to the formation of a pronounced fiber-like structure on its surface. The level of structural porosity can be adjusted by varying the working pressure during the process. A PEM treated this way can be subsequently coated with a thin layer of iridium, forming an anode-side catalyst-coated membrane (CCM) for applications in water electrolysis. Due to the significantly enlarged surface of the membrane, there is no necessity for any additional, potentially corroding, support nanoparticles to achieve efficient in-cell operation. Moreover, utilizing a rotatory frame-shaped substrate holder and a multitarget deposition apparatus, the sputter-etching process can be used in the preparation of a full anode/cathode thin-film CCM in a single vacuum entry. This structure yields remarkable performance characteristics in an electrolyzer cell, considering its low combined noble metal loading of just 220 μg cm−2. Using this completely dry process for CCM manufacturing may facilitate efficient large-scale future production.

Comprehensive understanding of the catalyst corrosion dynamics is a prerequisite for the development of an efficient cathode catalyst in proton-exchange membrane fuel cells. To reach this aim, the behavior of fuel cell catalysts must be investigated directly under reaction conditions. Herein, we applied a strategic combination of in situ/online techniques: in situ electrochemical atomic force microscopy, in situ grazing incidence small angle X-ray scattering, and electrochemical scanning flow cell with online detection by inductively coupled plasma mass spectrometry. This combination of techniques allows in-depth investigation of the potential-dependent surface restructuring of a PtNi model thin film catalyst during potentiodynamic cycling in an aqueous acidic electrolyte. The study reveals a clear correlation between the upper potential limit and structural behavior of the PtNi catalyst, namely, its dealloying and coarsening. The results show that at 0.6 and 1.0 VRHE upper potentials, the PtNi catalyst essentially preserves its structure during the entire cycling procedure. The crucial changes in the morphology of PtNi layers are found to occur at 1.3 and 1.5 VRHE cycling potentials. Strong dealloying at the early stage of cycling is substituted with strong coarsening of catalyst particles at the later stage. The coarsening at the later stage of cycling is assigned to the electrochemical Ostwald ripening process.

Platinum is the most widely used and best performing sole element for catalyzing the oxygen reduction reaction (ORR) in low-temperature fuel cells. Although recyclable, there is a need to reduce the amount used in current fuel cells for their extensive uptake in society. Alloying platinum with rare-earth elements such as yttrium can provide an increase in activity of more than seven times, reducing the amount of platinum and the total amount of catalyst material required for the ORR. As yttrium is easily oxidized, exposure of the Pt-Y catalyst layer to air causes the formation of an oxide layer that can be removed during acid treatment, leaving behind a highly active pure platinum overlayer. This paper presents an investigation of the overlayer composition and quality of Pt3Y films sputtered from an alloy target. The Pt3Y catalyst surface is investigated using synchrotron radiation X-ray photoelectron spectroscopy before and after acid treatment. A new substoichiometric oxide component is identified. The oxide layer extends into the alloy surface, and although it is not completely removed with acid treatment, the catalyst still achieves the expected high ORR activity. Other surface-sensitive techniques show that the sputtered films are smooth and bulk X-ray diffraction reveals many defects and high microstrain. Nevertheless, sputtered Pt3Y exhibits a very high activity regardless of the film's oxide content and imperfections, highlighting Pt3Y as a promising catalyst. The obtained results will help to support its integration into fuel cell systems.

This article presents an investigation of the sensing properties of chemiresistors based on Cu2O/CuO core–shell nanowires containing p–p′ heterojunctions. The nanowires were synthesized by a conven...

In this study, thin-film Pt catalysts with ultra-low metal loadings (ranging from 1 to 200 μg cm−2) were prepared by magnetron sputtering onto various carbon-based substrates. Performance of these catalysts acting as anode, cathode, or both electrodes in a proton exchange membrane fuel cell (PEMFC) was investigated in H2/O2 and H2/air mode. As base substrates we used standard microporous layers comprising carbon nanoparticles with polytetrafluoroethylene (PTFE) or fluorinated ethylene propylene (FEP) supported on a gas diffusion layer. Some substrates were further modified by magnetron sputtering of carbon in N2 atmosphere (leading to CNx) followed by simultaneous plasma etching and cerium oxide deposition. The CNx structure exhibits higher resistance to electrochemical etching as compared to pure carbon as was determined by mass spectrometry analysis of PEMFC exhaust at different cell potentials for both sides of PEMFC. The role of platinum content and membrane thickness was investigated with the above four different combinations of ionomer-free carbon-based substrates. The results were compared with a series of benchmark electrodes made from commercially available state-of-the-art Pt/C catalysts. It was demonstrated that the platinum utilization in PEMFC with magnetron sputtered thin-film Pt electrodes can be up to 2 orders of magnitude higher than with the standard Pt/C catalysts while keeping the similar power efficiency and long-term stability.

Dependence on noble metal catalysts is considered to be the main factor which hinders wider commercialization of proton exchange membrane fuel cells (PEM-FCs) and water electrolyzers (PEM-WEs). One way of lowering the loading of Pt and Ir is by using thin-film techniques for their deposition onto the high-surface conductive nanoparticles. Another approach, which is convenient in applications where the complete cycle of electricity - > H2 - > electricity takes place, is merging the PEM-WEs and PEM-FCs into one bi-functional system – the unitized regenerative fuel cell (PEM-URFC). In accordance with the above mentioned conception, this paper revolves around unconventionally prepared bi-functional magnetron sputtered lower-loading Pt-Ir catalysts for the anode side of PEM-URFC. Two geometries of catalyst coated membranes (CCM) were compared, differing in relative positioning of individual Pt and Ir thin films sputtered on TiC-based support sublayer; the sandwich-like Ir/TiC/Pt structure and the co-sputtered Pt-Ir/TiC structure. Wide arsenal of analytical methods, ranging from photoelectron spectroscopy to electrochemical atomic force microscopy determined that co-sputtering of Pt and Ir leads to alloy formation, thus preventing iridium to fully electro-oxidize to IrOx which in turn helps to explain why sandwich-like Ir/TiC/Pt structure, with no alloy, outperforms the co-sputtered Pt-Ir/TiC CCM in both operational regimes despite having the exactly same noble metal loading. The PEM-URFC single cell with sandwich-like bi-functional anode catalyst yielded 31.8% of round-trip efficiency at 1 A cm−2 in comparison to 34.2% achieved by combination of single-purpose cells with more than double the loading of noble metals.

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 SnO2 and Pd-doped SnO2 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 SnO2 nanostructures while annealing of the substrate during deposition affected the films crystallinity. Also, we found out that doping of the SnO2 films with Pd leads to alloy phase formation. These findings can be applied in variety of applications including gas sensing, catalysis, optics and electronics.

The effect of ZnO and the preparation method of ZnO/ZrO2–SiO2 catalysts on their acid–base properties and catalytic performances in the conversion of diluted ethanol mixtures into 1,3-butadiene (BD) is presented. Based on the results of the temperature-programmed desorption (TPD) of NH3/CO2, near-ambient pressure X-ray photoelectron spectrometry (NAP-XPS) with O2/ethanol + H2O, adsorption of pyridine and deuterated chloroform followed by Fourier-transform infrared (FTIR) spectroscopy, and catalytic experiments, it has been concluded that the differences in activities and selectivities of the prepared catalysts can be attributed to the formation of different amounts of Zn-containing acidic or basic active sites. A wet-kneading procedure facilitates the preparation of a more active/selective catalyst as compared to that obtained using the incipient wetness impregnation of ZrO2–SiO2 with an aqueous solution of zinc salt. Dependencies between the acid–base capacity ratio of zinc oxides, calculated from the NH3/CO2-TPD and NAP-XPS data as well as the initial reaction rate of BD formation have been observed for ZnO/ZrO2–SiO2 catalysts. In the presence of a catalytic system with a predominance of acidic sites on the surface, higher ethanol conversion and BD selectivity can be achieved as opposed to systems involving a predominance of basic sites. The ZnO/ZrO2–SiO2 catalyst prepared by using zinc oxide nanoparticles and ZrO2–SiO2 provides a BD yield of ∼52.4% in the conversion of 80% ethanol–20% H2O mixture (673 K, 1.3 gEtOH gcat−1 h−1); a BD productivity of 0.4 gBD gcat−1 h−1 can be achieved.

The study focuses on antibacterial Cu/C:F nanocomposites deposited onto polyether-ether-ketone (PEEK) substrates. The nanocomposites were prepared by means of physical vapour deposition; copper nanoparticles (NPs), produced with the use of a gas aggregation source, were coated with RF sputtered polytetrafluorethylene. It was found that nanocomposites, formed with a properly tailored number of Cu NPs and C:F barrier thickness, offer a strong antibacterial effect against E. coli without any harm to MG63 cells.

In this work, for the first time, we describe the design and synthesis of novel fluorinated poly(arylene ether)/silica cross-linked materials (FPAE/SiO1.5) through a sol-gel process by using the triethoxysilyl-containing fluorinated polyethers as precursors for both organic and inorganic networks formation. The polyether-based precursors with the sol-gel active species were synthesized via hydrosilylation reaction between triethoxysilane and the corresponding allyl-functionalized FPAE under Pt catalysis. Herein, we present two approaches of hydrolysis triethoxysilane groups to silanol ones within sol-gel chemistry: (1) hydrolysis with air moisture and (2) hydrolysis of the ethoxysilyl groups at the interface between two liquids. The mechanical and thermal properties of the FPAE/SiO1.5 materials were studied depending on the structure of macromolecular chains and synthetic route. Scanning electron and atomic force microscopies were employed to investigate the morphology of the resulting silica-containing cross-linked materials. The resulting FPAE/SiO1.5 films were flexible and tough with tensile strength above 25 МPа, and exhibited high thermal stability, having the initial decomposition temperature about 300°С. For more detailed explanation of the thermophysical behavior of the FPAE/SiO1.5 materials, the synthesis method of new silica-containing organic-inorganic system was developed by the direct hydrosilylation reaction between allyl-functionalized polyethers and 1,1,3,3-tetramethyldisiloxane. All films exhibited high hydrophobic properties (water contact angles above 102°), low dielectric constants and losses at room temperature. In particular, the FPAE/SiO1.5 film prepared from tetrafluorobenzene-based polyether showed the ultra-low dielectric constant of 1.86 at 10 kHz. This makes the obtained polymer FPAE/SiO1.5 materials attractive for microelectronics and many other emerging applications.

International audience; ZnLaZrSi oxide systems prepared with a silica component of the different nature have been studied in 1,3-butadiene production from aqueous ethanol. The following silica materials were used: KSKG, A-175, A-380, SBA-15, MCM-41, MCM-48, MCF, and dealuminated BEA zeolites. The characteristics of the porous structure of the silica support, such as porosity, pore size distribution, and specific and external surface areas, were found not to be critical parameters for achieving a high 1,3-butadiene yield during the EtOH–H2O mixture conversion in the presence of ZnLaZrSi oxide catalysts. On the contrary, the quantity and strength of Lewis acid sites, which in turn differ depending on the choice of silica material, have a significant impact on 1,3-butadiene selectivity and yield. The highest values of the selectivity of 1,3-butadiene formation (up to 68%) and yield as well as stability toward deactivation in the presence of H2O were achieved over ZnLaZr–KSKG, ZnLaZr–SBA-15, and ZnLa–Zr1SiBEA (with mononuclear isolated tetrahedral Zr(IV) species). The productivity of ZnLa–Zr1SiBEA catalyst accounts for 0.324 g1,3-BD·gcat–1·h–1 (T = 648 K, WHSV = 2.88 h–1, 80 vol % EtOH in water as an EtOH source). The main reason for the decrease in 1,3-butadiene yield in the presence of H2O in the reaction mixture was shown to be a deactivation of acetaldehyde condensation sites on the catalyst surface, while the rate of acetaldehyde formation decreases slightly. According to 1H–13C CP/MAS NMR spectroscopic results, the use of aqueous ethanol as the feed for the ethanol-to-butadiene process is very advantageous to prevent the carburization of the catalysts.

Platinum is the most widely used and best performing sole element for catalyzing the oxygen reduction reaction (ORR) in low-temperature fuel cells. Although recyclable, there is a need to reduce the amount used in current fuel cells for their extensive uptake in society. Alloying platinum with rare-earth elements such as yttrium can provide an increase in activity of more than seven times, reducing the amount of platinum and the total amount of catalyst material required for the ORR. As yttrium is easily oxidized, exposure of the Pt-Y catalyst layer to air causes the formation of an oxide layer that can be removed during acid treatment, leaving behind a highly active pure platinum overlayer. This paper presents an investigation of the overlayer composition and quality of Pt

PtCu bimetallic alloys are known to provide better activity than pure platinum in proton exchange membrane fuel cells. However, such catalysts undergo complex degradation processes during fuel cell operation, resulting in deterioration of their activity. By using in situ electrochemical (EC) atomic force microscopy combined with in situ EC infrared reflection absorption spectroscopy, we provide a comprehensive investigation of morphological and structural transformations of PtCu model thin film catalysts during accelerated degradation tests (ADTs). The ADTs consist of potentiodynamic cycling to three different upper potentials relevant for different modes of fuel cell operation. The results show that, depending on the upper potential limit, PtCu alloy electrocatalysts are subject to drastic changes in the surface composition, morphology, and structure.

In this study, the performance of the thin film Pt catalyst with loading in the range of 1–200 µg/cm2 prepared by magnetron sputtering was investigated for both anode and cathode sides of a proton exchange membrane fuel cell (PEMFC) in H2/O2 and H2/air modes (see example of anode study in Fig.1). Standard microporous layers comprising carbon nanoparticles and Teflon PTFE and FEP supported gas diffusion layer, as well as their modifications by magnetron deposition of carbon in N2 atmosphere (leading to CNx) followed by plasma etching were used as substrates for Pt deposition (Fig.1 right). The choice of CNx interlayer was motivated by the higher resistance of the CNx structure as compared to pure C which was determined by a mass-spectrometry analysis of PEMFC exhaust at different cell potentials. Benefits of lower absolute carbon etching rate and at least 0.25 V lower corrosion threshold were found for CNxon both sides of the PEMFC (see Fig. 2 for cathode results). The anode catalysts with various Pt loadings on all the substrates were tested and compared with a standard state-of-the-art commercial Pt/C reference anode with respect to their efficiency for hydrogen oxidation reaction (HOR; see Fig. 1). Performance up to 1.3 W/cm2 in pure H2 and O2 was achieved for anodes containing Pt loading of 2–10 µg/cm2 on CNx substrate. It is comparable to the performance of a standard commercial Pt/C anode with loadings 200–400 µg/cm2. The same experiments as for HOR were performed for and oxygen reduction reaction (ORR). In this саsе, cathodes with various Pt loadings were tested. The maximum performance up to 0.54 W/cm2 in pure H2 and O2 was found for cathodes with Pt loadings in the range of 20–100 µg/cm2. The Pt loading of 100 µg/cm2 was found as the limit thickness for the magnetron sputtered thin film, further increase of Pt content leads to efficiency decrease of PEMFC. When PEMFC is switched from H2/O2 to the H2/air, the power is decreased 2.0 to 2.2-times relative to the reference Pt/C powder electrodes and 2.8 to 3.0-times on thin film Pt electrodes. We have also performed 450-hour durability tests in a pulsed regime of 30min open voltage + 30 min under 400 mA/cm2 load, as well as in the regime of stable 400 mA/cm2load for both anode and cathode sides of the PEMFC with Pt loadings of 2 µg/cm2 and 20 µg/cm2. Based on our research, the PEMFC with best Pt utilization was found for MEA based on a combination of anode with 2 µg Pt per cm2 and cathode with 10 µg Pt per cm2, yielding the total power density 0.45 W/cm2 for as little as 12 µg/cm2 of total noble metal content. Figure 1

As-deposited Pt-Ni and annealed Pt-Ni alloy catalyst films prepared by magnetron co-sputtering were investigated in order to quantify their ageing during accelerated durability test. The parameters of the durability test were chosen to simulate severe potential conditions that may occur at start-up/shut-down cycles of a fuel cell. Using in situ electrochemical atomic force microscopy complemented with ex situ energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, synchrotron radiation photoelectron spectroscopy and X-ray diffraction provided step-by-step correlation of chemical and morphology changes induced by catalyst’s aging processes. We show that the as-deposited Pt-Ni films face severe chemical stability problem which leads to almost complete destruction of the alloy during the durability test. On the other hand Pt-Ni films annealed in vacuum are more resistive to morphological and chemical changes. It was confirmed that upon annealing due to redistribution of Pt and Ni atoms Pt-skin is formed on catalyst surface, which is responsible for a better stability during the aging test.

Uniform distribution of filler particles in a polymer matrix is crucial to the improvement of properties of polymer composites. In this work, we have shown that control of the polymerization rate by addition of the catalyst (Fe(acac) 3 ) hinders filler aggregation and enhances electrical and mechanical properties of polyurethane/nanotube composites. Thus, a percolation threshold value of 0.02 wt % obtained for the composites with the catalyst was much lower than the value of 0.65 wt % for the composites without the catalyst. Moreover, the electrical conductivity of the catalytically prepared composites at a nanotube content of 3 wt % was two orders of magnitude higher than that of the non-catalytically prepared ones. The tensile strength of both types of composites showed an improvement at lower filler concentrations, however, the increase of filler content led to deterioration of the mechanical properties for the non-catalytically prepared composites. Structure of the composites was investigated by means of optical and scanning electron microscopy. Additionally, the current-voltage characteristics (J-E) of the composites were studied.

Gradient surfaces, i.e. surfaces whose properties change gradually along the sample length, receive increasing attention as they facilitate optimization of surface properties for particular applications. In this study we present vacuum-based strategy for fabrication of irregular silver nanoparticle arrays with gradient optical properties. This approach is based on the magnetron sputtering of Ag performed at low pressure in argon atmosphere. The gradient character of deposited arrays is achieved by use of a movable mask that is introduced in the vicinity of the substrate. It is shown that this technique enables to tailor the course of the gradient of localized surface plasmon resonance (LPSR) either by the speed of the mask or by additional deposition of silver on the top of surface pre-seeded by the gradient nanoparticle arrays.

We report and compare two vacuum-based strategies to produce Ag/Au materials characterized by double plasmon resonance peaks: magnetron sputtering and method based on the use of gas aggregation sources (GAS) of nanoparticles. It was observed that the double plasmon resonance peaks may be achieved by both of these methods and that the intensities of individual localized surface plasmon resonance peaks may be tuned by deposition conditions. However, in the case of sputter deposition it was necessary to introduce a separation dielectric interlayer in between individual Ag and Au nanoparticle films which was not the case of films prepared by GAS systems. The differences in the optical properties of sputter deposited bimetallic Ag/Au films and coatings consisted of individual Ag and Au nanoparticles produced by GAS is ascribed to the divers mechanisms of nanoparticles formation.

A new method based on transformation of magnetron sputtered platinum thin films into platinum nanostructures enclosed by high-index facets, using electrochemical potential cycling in a twin working electrode system is reported. The controllable formation of various Pt nanostructures, described in this paper, indicates that this method can be used to control a selective growth of high purity Pt nanostructures with specific shapes (facets or edges). The method opens up new possibilities for electrochemical preparation of nanostructured Pt catalysts at high yield.

Atmospheric air plasma treatment of chitosan solutions leads to degradation of chitosan molecules by OH radicals and is accompanied by a predominant cleavage of glycosidic linkages and by a decrease of the molecular weight. The degradation proceeds via first order kinetics with the rate constant of (5.73 ± 0.22) × 10−6 s−1 and the energetic yield of chitosan bond scission of (2.4 ± 0.2) × 10−8 mol/J. Products of degradation together with intact chitosan molecules adsorb and form coatings on polypropylene foils immersed into the solution that is being plasma treated. The plasma treatment results in strong binding of chitosan to polypropylene due to the formation of covalent bonds between the activated polymer surface and chitosan molecules. Plasma-driven crosslinking is responsible for the accumulation of compressive stress which leads to the development of buckling instabilities in the chitosan coatings.

Polycrystalline cerium oxide thin films (15 nm) deposited on a glassy carbon substrate were used as an electrode in a mediator-free, non-enzymatic electrochemical sensor for hydrogen peroxide. The electrode surface was characterized by X-ray photoelectron spectroscopy, resonant photoelectron spectroscopy, scanning electron microscopy and atomic force microscopy. The electrode sensitivity, detection limit and pH range of sensor stability were determined by applying electrochemical techniques: cyclic voltammetry and chronoamperometry. It was found that the sensor reactivity to H2O2 is directly related to the presence of electroactive cerium centres of 3+ character on the electrode surface. The Michaelis–Menten mechanism of catalase-like activity of ceria film is suggested as an explanation of the data and discussed. The results confirmed the sensing abilities of technologically well-accessible nanostructured cerium oxide films for hydrogen peroxide detection without using a mediator, i.e. the enzymatic properties of CeO2/GC electrode.

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.

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.

Nowadays, electrochemistry has a considerable technological impact, involving fuel cells, super capacitors and batteries. These devices are based on complex architectures, which complicates monitoring their evolution in situ under operating conditions to reveal the reasons for reduced lifetime and performances. Here, we present a design of a multipurpose electrochemical cell for grazing incidence small and wide angle X-ray scattering (GISAXS and GIWAXS) where the environment for operating conditions can be recreated. We focus on proton exchange membrane fuel cells (PEMFCs) which operational conditions are simulated by means of potentiodynamic-based accelerated stress tests, applied to a thin film of Pt nanoparticles representing a model system of a benchmark catalyst. Two different upper potentials are used to mimic fuel cell operating conditions: at 1.0 V RHE the catalyst film preserves its initial morphology, while at 1.5 V RHE (simulating fuel cell start-up/shut-down cycles) significant coarsening has been observed. The initial dimension of the Pt particles of 4.0 nm increases to 8.7 nm due to the predominant process of coalescence and final Ostwald ripening. In parallel, the distance between the particles increases, the catalyst film (9 nm thick) becomes thinner at first and exhibit a higher roughness at the end.

Histidine adsorption from neutral aqueous solution on cerium oxide substrates was studied by photoemission with use of synchrotron radiation, soft X-ray absorption spectroscopy and nuclear magnetic resonance. Polycrystalline oxide films and oxide nanoparticles were used as ceria substrates. Independent of the morphology of the support, histidine binds to the oxide through the carboxylic group while the imidazole ring does not participate in the interface formation. Compared to deposition of molecules by evaporation in vacuum, the presence of the solution during adsorption does not alter the histidine bonding to cerium oxide. The present results clearly demonstrate the applicability of the model ( in-situ ) studies of the histidine/CeO 2 interface to the biocompatible techniques of cerium oxide functionalization.

A Pt-Co nanoalloy thin film catalyst was prepared by using simultaneous magnetron sputtering of Pt and Co. The catalyst was characterized during accelerated degradation test using in-situ electrochemical atomic force microscopy complemented with ex-situ techniques such as energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and synchrotron radiation photoelectron spectroscopy. The combined results gave the full step-by-step picture of the catalyst behavior during the aging test.

Proton exchange membrane (PEM) water electrolysis (PEMWE) is getting more attention in recent years as a promising alternative in context of energy storage from renewables. However high prices of platinum and iridium, currently considered to be the state-of-the-art electrocatalysts, prevent wider commercialization of this technology. In this paper, we present unconventional and cost-effective preparation method of anode catalyst, containing low amount of noble metal. Thin Ir film is magnetron sputtered on TiC-based support sublayer, hot-pressed on anode side of Nafion® N115 PEM. Following three parameters were systematically varied and their impact on PEMWE in-cell performance was evaluated: total TiC-based support material loading on the PEM, ionomer content within the support sublayer and Ir catalyst loading on top of the support sublayer. In addition, TiC-based sublayer underwent accelerated aging procedure, followed by photoelectron spectral analysis to prove its ability to withstand high anodic potentials. Remarkable PEMWE in-cell performances were obtained, considering amount of used Ir; 1.74 V (with ∼80 μg cm−2 of Ir), 1.72 V (with ∼160 μg cm−2 of Ir) and 1.71 V (with ∼240 μg cm−2 of Ir) at 1 A cm−2 and 80 °C.

Pt-doped CeOx thin film electrocatalysts have recently been shown to exhibit high activity and stability at the anode of proton exchange membrane fuel cells (PEM-FC). To identify the role of the Pt dopant and the origin of the high stability of Pt–CeOx films, we applied electrochemical in situ IR spectroscopy on Pt–CeOx model thin film catalysts during methanol (1 M methanol) oxidation. The model catalysts were prepared by magnetron cosputtering of Pt (9–21 atom %) and CeO2 onto clean and carbon-coated Au supports. All samples were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) before and after reaction. At pH 1 (0.1 M HClO4) the Pt–CeOx dissolves partially during potential cycling, whereas the films are largely stable at pH 6 (0.1 M phosphate buffer). Electrochemical IR spectroscopy of the adsorbed CO shows that metallic Pt is formed on all Pt–CeOx samples during methanol oxidation. In comparison to Pt(111), Pt a...

Candle soot deposited from the candle flame was used as a catalyst support for an anode catalyst in a proton exchange membrane fuel cell. The results showed that Pt/soot hybrids prepared by magnetron sputtering of 5 nm platinum films on candle soot exhibit very high mass activity in the fuel cell, which is more than one order of magnitude higher than that for commercial catalyst. The elementary preparation, high surface-to-volume ratio, good conductivity and hydrophobicity make candle soot a promising type of the support for PEMFCs catalyst.

TiO2 thin films with developed structure were deposited by means of a hollow cathode plasma jet (HCPJ) in a DC regime with a supporting anode. The influence of the plasma temperature on the surface morphology and crystalline structure of the thin films under different deposition conditions was studied. Diagnostics of the thin films structure was carried out using XRD, SEM, EDX and TEM methods. One batch of samples was annealed at a temperature of 400 °C in atmospheric conditions as a comparison with the crystalline structure and morphology of unannealed samples. The presence of two crystalline polymorphs of rutile and anatase in the films was discussed. The vacuum system was improved for an extended deposition of non-conductive materials without terminating the discharge and cleaning of the deposition chamber. The aim of this investigation was to prepare the vacuum system for the fabrication of photo electrodes which are the main functional part in dye-sensitized solar cells. The test DSSCs (dye-sensitized solar cells) were prepared from low-cost materials (raspberry/hibiscus natural dye-sensitizers and candle soot counter electrode) in order to check the quality of the films, with a highest conversion efficiency η = 0.66% and a fill factor FF = 62%.

Recently we have tested a magnetron sputtered Pt-Co catalyst in a hydrogen-fed proton exchange membrane fuel cell and showed its high catalytic activity for the oxygen reduction reaction. Here we present further investigation of the magnetron sputtered Pt-Co thin film catalyst by both experimental and theoretical methods. Scanning electron microscopy and transmission electron microscopy experiments confirmed the nanostructured character of the catalyst. The surface composition of as-deposited and annealed at 773 K Pt-Co films was investigated by surface analysis techniques, such as synchrotron radiation photoelectron spectroscopy and X-ray photoelectron spectroscopy. Modeling based on density functional theory showed that the surface of 6 nm large 1:1 Pt-Co nanoparticles is almost exclusively composed of Pt atoms (>90%) at typical operation conditions and the Co content does not exceed 20% at 773 K, in agreement with the experimental characterization of such films annealed in vacuum. According to experiment, the density of valence states of surface atoms in Pt-Co nanostructures is shifted by 0.3 eV to higher energies, which can be associated with their higher activity in the oxygen reduction reaction. The changes in electronic structure caused by alloying are also reflected in the measured Pt 4f, Co 3p and Co 2p photoelectron peak binding energies.

Surfaces whose properties change gradually along the sample length, so-called gradient surfaces, are highly interesting for fundamental studies focused on the interaction between biomolecules or cells and surfaces. In this study, we investigate simple, vacuum-based strategy for fabrication of surfaces with gradient nanoroughness and wettability. This approach is based on the application of gas aggregation source of nanoparticles combined with the magnetron sputtering of poly(tetrafluoroethylene). It is shown that this technique makes it possible to produce coatings with invariant surface chemistry, but with gradient roughness in the range 0.5–20 nm and wettability gradient that ranges from 100° up to 150°, i.e., coatings with hydrophobic to superhydrophobic character.