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The scarce supply of Ir used to catalyze the sluggish oxygen evolution reaction in acidic water electrolysis calls for unconventional approaches to design more active catalysts with minimal resource usage for their commercial scaling. Industrial-ready production methods and laboratory scale tests that can reflect the catalyst behaviour realistically need to be included in this process. In this work, we benchmarked three series of self-supported Ir–Co catalysts with low Ir loading produced by physical vapour deposition under relevant current densities in a gas diffusion electrode setup. It was seen that after selective acid leaching of the Co, a nanoporous structure with a high electrochemically active surface area and a mixed oxide and metallic character was formed. Depending on the initial Co:Ir deposition ratio over ten times higher oxygen evolution mass activities could be reached as compared to a commercial, unsupported IrOx nanoparticle catalyst used as a benchmark in the same setup configuration. The presented integrative catalyst design and testing strategy will help to facilitate bridging the gap between research and application for the early introduction of next-generation catalysts for water splitting.

The splitting of carbon dioxide was investigated for a coaxial dielectric barrier discharge, which was operated with nanosecond high-voltage pulses of 500 ns and amplitudes up to 20 kV at ambient temperature and atmospheric pressure. A non-thermal plasma could be established across a gap distance of 4 mm and a length of 90 mm for gas flows of 30–210 sccm of pure CO2 and with admixtures of Argon. The application of high-voltage pulses of either positive or negative polarity resulted in distinct differences in effective conversion and CO production. The highest observed conversion of 6.6%, corresponding to a CO production of 7%, was achieved for positive high-voltage pulses of 20 kV that were applied with a repetition rate of 3 kHz for a ratio of CO2:Ar of 1:2 at a flow rate of 30 sccm. Conversely, an operation with negative high-voltage pulses, for otherwise the same operating parameters, resulted in an effective conversion of only 5.3% and CO production of 5.4%. The corresponding conversion rates for specific energy input (SEI), concerning different operating parameters, could be related to reaction enthalpies that were calculated from thermodynamic functions. The differences in polarity were associated with discharge characteristics, i.e., plasmas appeared more filamentary for positive high-voltage pulses. In this case, a visible plasma could also be established for much lower pulse amplitudes. Graphical Abstract

The first plasma-assisted immobilization of an organocatalyst, namely a bifunctional phosphonium salt in an amorphous hydrogenated carbon coating, is reported. This method makes the requirement for prefunctionalized supports redundant. The immobilized catalyst was characterized by solid-state 13 C and 31 P NMR spectroscopy, SEM, and energy-dispersive X-ray spectroscopy. The immobilized catalyst (1 mol %) was employed in the synthesis of cyclic carbonates from epoxides and CO2 . Notably, the efficiency of the plasma-treated catalyst on SiO2 was higher than those of the SiO2 support impregnated with the catalyst and even the homogeneous counterpart. After optimization of the reaction conditions, 13 terminal and four internal epoxides were converted with CO2 to the respective cyclic carbonates in yields of up to 99 %. Furthermore, the possibility to recycle the immobilized catalyst was evaluated. Even though the catalyst could be reused, the yields gradually decreased from the third run. However, this is the first example of the recycling of a plasma-immobilized catalyst, which opens new possibilities in the recovery and reuse of catalysts.

Due to the slow kinetics of the oxygen evolution reaction (OER), high precious metal loadings are currently required at the anode of proton exchange membrane (PEM) electrolyzers. In this work, we present a novel, scalable and efficient method for the fabrication of high surface area iridium-based electrocatalysts. Using alternating sputtering of iridium and cobalt, followed by selective leaching, we produce a self-supported and highly active OER electrocatalysts for acidic environments. Nanostructured IrOx-networks present a bulk-like behaviour, with a site-specific activity similar to that of extended polycrystalline IrOx surfaces. Moreover, in terms of mass activity, the IrOx-networks are among the most active Ir-based catalysts reported, presenting a mass activity enhancement by a factor of eight over commercial Ir-black nanoparticles. These novel self-supported Ir-based networks are very stable, which, combined with their enhanced mass activity, makes them promising anode catalysts for PEM electrolyzers.

The development of catalysts for the oxygen reduction reaction in low-temperature fuel cells depends on efficient and accurate electrochemical characterization methods. Currently, two primary techniques exist: rotating disk electrode (RDE) measurements in half-cells with liquid electrolyte and single cell tests with membrane electrode assemblies (MEAs). While the RDE technique allows for rapid catalyst benchmarking, it is limited to electrode potentials far from operating fuel cells. On the other hand, MEAs can provide direct performance data at realistic conditions but require specialized equipment and large quantities of catalyst, making them less ideal for early-stage development. Using sputtered platinum thin-film electrodes, we show that gas diffusion electrode (GDE) half-cells can be used as an intermediate platform for rapid benchmarking at fuel-cell relevant current densities (~1 A cm&minus, 2). Furthermore, we demonstrate how different parameters (loading, electrolyte concentration, humidification, and Nafion membrane) influence the performance of unsupported platinum catalysts. The specific activity could be measured independent of the applied loading at potentials down to 0.80 VRHE reaching a value of 0.72 mA cm&minus, 2 at 0.9 VRHE in the GDE. By comparison with RDE measurements and Pt/C measurements, we establish the importance of catalyst characterization under realistic reaction conditions.

Nanostructuring of electrocatalysts is an important aspect of catalyst design as catalytic performance depends not only on the specific activity (reaction rate per surface area), but also on the dispersion of the catalyst. We present an industrially compatible, but effective preparation method for support-free nanostructured catalyst layers. Alternating sputtering was used to prepare heterogeneous Pt Cu templates ranging from 95 up to 99.5 at. % Cu. These templates were then electrochemically leached to form a nanostructured Pt Cu network and benchmarked with respect to the oxygen reduction reaction. It is shown that the templates with lower Cu:Pt ratios exhibit the highest initial specific activity but have a relatively low electrochemically active surface area. Subjecting the samples to extended accelerated stress tests, it is found that the support-free nanostructured Pt Cu networks are relatively resistant to high potential cycling, which can be explained by the lack of carbon corrosion. The loss in electrochemical surface area thereby depends on the initial Pt content. The specific oxygen reduction activity, however, approaches the value of bulk Pt. Although this decrease is not desirable, still an (specific) activity improvement of two to four times as compared carbon supported nanoparticles can be preserved.

Several concepts for platinum-based catalysts for the oxygen reduction reaction (ORR) are presented that exceed the US Department of Energy targets for Pt-related ORR mass activity. Most concepts achieve their high ORR activity by increasing the Pt specific activity at the expense of a lower electrochemically active surface area (ECSA). In the potential region controlled by kinetics, such a lower ECSA is counterbalanced by the high specific activity. At higher overpotentials, however, which are often applied in real systems, a low ECSA leads to limitations in the reaction rate not by kinetics, but by mass transport. Here we report on self-supported platinum–cobalt oxide networks that combine a high specific activity with a high ECSA. The high ECSA is achieved by a platinum–cobalt oxide bone nanostructure that exhibits unprecedentedly high mass activity for self-supported ORR catalysts. This concept promises a stable fuel-cell operation at high temperature, high current density and low humidification. A high oxygen reduction reaction activity can usually be realized by increasing platinum specific activity at the expense of active surface area. Self-supported platinum–cobalt-oxide networks combining high activity and surface area now promise a stable fuel-cell operation.

Proton exchange membrane electrolysis is one of the key technologies for the implementation of renewable energy. The main advantage is the conversion of electrical energy into storable chemical energy. The objective of this work is to enhance our understanding of protective coatings for carbon-polymer composite compound materials used as bipolar plates in acidic electrolysis cells. A two-step plasma process was developed to deposit a corrosion protection. As a first step, the composite compound surface was roughened by applying RF high voltage and using it as a powered electrode. As a second step, titanium coatings were deposited by pulsed DC magnetron sputtering. The plasma process was monitored by in-situ temperature measurements. The corrosion resistance of the coated compound surface was evaluated by cyclic voltammetry and chronoamperometry at 2 V vs. SHE as well as light microscopy. Furthermore, we analysed the activation effect by SEM; the titanium coatings were analysed by the van-der-Pauw method and SEM.

Dry reforming of propane (DRP) with CO2 was examined over iron–ceria spinel (FeCe2O4) that was synthesized on mesoporous alumina foam by the sol–gel method. The FeCe2O4/Al-F catalyst exhibited significant catalytic activity for the DRP with propane and CO2 conversions of 93% and 76%, respectively. Moreover, the redox behavior of the spinel was found to greatly reduce the deposition of carbon, which could be attributed to the oxidation of surface carbon to CO via the interaction with FeCe2O4 lattice oxygen. The FeCe2O4/Al-F catalyst with good catalytic activity, long-term stability and coke resistance may be a promising candidate for the DRP.

Ultra-low Pt-loaded (3–54 µg cm− 2) gas diffusion electrodes were prepared by a direct current unbalanced magnetron sputtering process. Pt films were deposited directly onto the microporous layer of the gas diffusion electrode and tested in a half-cell and proton exchange membrane fuel cell. While the apparent activity towards oxygen reduction reaction under half-cell conditions is dependent on Pt loading, mass activity is Pt loading independent, indicating constant catalyst utilization. Assuming the validity of the porous electrode model, kinetic parameters are extracted from the experimental data. Unlike the results from the half-cell study, the U–I curves of the proton exchange membrane fuel cell at different loadings show a decrease of the catalyst utilization at higher Pt loadings. The Pt structure on the gas diffusion electrode was investigated by electron microscopy, atomic force microscopy and X-ray diffraction.

By implementing a low-temperature plasma pretreatment step in the processing procedure for separating different sulfide mineral mixtures, it has been possible to improve the efficiency of froth flotation. Two powder mixtures consisting of pyrite/chalcopyrite and chalcopyrite/molybdenite were selectively oxidized in an Ar/O2 microwave plasma. The oxide/sulfur mixture obtained was separated by using an oxide collector. The recovery of each mixture component was measured and the results were compared with the untreated material. For separating the pyrite/chalcopyrite mixture, high selectivity could be achieved after plasma pretreatment using the oxide collector Flotinor FS-2. One hundred percent of chalcopyrite could be recovered whilst the recovery rate of pyrite remained below eight percent. Additionally, major improvements could be achieved in the efficiency of separating the chalcopyrite/molybdenite mixtures. In all cases, it was possible to avoid the use of activating and depressant reagents, which successfully demonstrates that the surface oxidation selectivity of the plasma pretreatment ensures high flotation efficiencies by using an oxide collector to separate the sulfide mixture. Additional XPS measurements have been carried out to investigate the oxidation of the sulfide surface.

The first plasma‐assisted immobilization of an organocatalyst, namely a bifunctional phosphonium salt in an amorphous hydrogenated carbon coating, is reported. This method makes the requirement for prefunctionalized supports redundant. The immobilized catalyst was characterized by solid‐state 13C and 31P NMR spectroscopy, SEM, and energy‐dispersive X‐ray spectroscopy. The immobilized catalyst (1 mol %) was employed in the synthesis of cyclic carbonates from epoxides and CO2. Notably, the efficiency of the plasma‐treated catalyst on SiO2 was higher than those of the SiO2 support impregnated with the catalyst and even the homogeneous counterpart. After optimization of the reaction conditions, 13 terminal and four internal epoxides were converted with CO2 to the respective cyclic carbonates in yields of up to 99 %. Furthermore, the possibility to recycle the immobilized catalyst was evaluated. Even though the catalyst could be reused, the yields gradually decreased from the third run. However, this is the first example of the recycling of a plasma‐immobilized catalyst, which opens new possibilities in the recovery and reuse of catalysts., Plasma will fix it: Plasma polymerization is used to immobilize a phosphonium salt organocatalyst (Pcat) in an amorphous hydrogenated carbon coating on unfunctionalized metal oxide supports. The resulting catalysts are employed in the synthesis of cyclic carbonates from epoxides and CO2 in up to 99 % yield under mild conditions. Furthermore, the unprecedented recycling of a catalyst immobilized by a plasma technique is reported.

This work presents the oxygen reduction reaction (ORR) activity of three different plasma-synthesized cobalt oxides supported on carbon (CoOx/C) in 0.1 M KOH and 0.1 M K2CO3 at 323 and 348 K. To evaluate the stability of the catalyst material, cyclic voltammograms (CVs) were recorded. To investigate the catalytic activity, a high-temperature rotating ring-disk electrode (RRDE) was used. Cobalt based catalyst materials seem to be a good alternative to costly platinum-based catalysts. This work shows the temperature dependent catalytic activity of plasma-treated cobalt acetate precursor material. This work showed that the increase of temperature to 323 K resulted in an increase in activity for ORR for the three catalyst materials, but a further temperature increase up to 348 K leads to a decrease in activity.

Plasma-synthesized cobalt oxide supported on carbon has been analyzed for its use for electrocatalytic oxygen reduction reaction (ORR) in alkaline anion exchange membrane fuel cells (AEMFC). This work presents the ORR activity in 0.1 mol L−1 KOH and 0.1 mol L−1 K2CO3 at 25 °C. Cyclic voltammetry (CV) was used to determine the potentials at which the ORR occurs and to evaluate the stability of catalyst. Moreover, a rotating ring-disk electrode (RRDE) was used to investigate the activity of the catalysts and the formation of the by-product hydroperoxide anion (HO2 −) as well as to identify the preferred pathway of the ORR. Calculated kinetic parameters for the ORR for the cobalt catalysts are shown in this work together with a comparison to a commercial platinum catalyst. However, the cobalt oxide produced more by-products which could lead to damage of the membrane in a fuel cell through a radical attack of the polymer backbone.

Titania is a promising material for numerous photocatalytic reactions such as water splitting and the degradation of organic compounds (e.g., methanol, phenol). Its catalytic performance can be significantly increased by the addition of co-catalysts. In this study, Au and Au/Ag nanoparticles were deposited onto mesoporous titania thin films using photo-deposition (Au) and magnetron-sputtering (Au and Au/Ag). All samples underwent comprehensive structural characterization by grazing incidence X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Nanoparticle distributions and nanoparticle size distributions were correlated to the deposition methods. Light absorption measurements showed features related to diffuse scattering, the band gap of titania and the local surface plasmon resonance of the noble metal nanoparticles. Further, the photocatalytic activities were measured using methanol as a hole scavenger. All nanoparticle-decorated thin films showed significant performance increases in hydrogen evolution under UV illumination compared to pure titania, with an evolution rate of up to 372 &mu, L H2 h&minus, 1 cm&minus, 2 representing a promising approximately 12-fold increase compared to pure titania.

The nature and physical parameters of dielectric barrier discharges (DBDs) are determined by the presence of dielectric material in the discharge gap. The charging of the dielectric barrier is responsible for the non-thermal regime as it limits the local energy dissipation. In an operating DBD residual surface charges can influence the distribution and development of the plasma in the following discharge cycles1. In order to learn more about residual surface charge role an experiment with a rotating dielectric electrode and a pin electrode (325 μm tip radius) is realized2. The rotating dielectric barrier enables DBD-operation with DC high voltage and, the remaining surface charges are removed by a second grounded electrode which is sliding over the dielectric. Thus, single, repetitive microdischarges in air at atmospheric pressure are ignited without participation of residual surface charges. These microdischarges were investigated by ICCD camera, electrical measurements and time-correlated single photon counting (sub-ns, sub-mm and spectral resolution). For positive polarity of the pin electrode a positive streamer starting from the middle of the gap followed by a secondary wave starting from the metal electrode is observed. For negative polarity an anode directed wave of light and a weaker glow in front of the cathode are obtained.

Metal nanoparticles are commonly used for a wide range of applications. This paper presents a novel synthesis method using plasma vapor deposition and a subsequent thermal treatment to produce homogeneous particles within the nanometer range. A combination of high resolution transmission electron microscopy and scanning electron microscopy studies as well as ultraviolet/visible light transmission measurements are employed in order to characterize crystallographic, microstructural, and optical properties of gold, silver, and core–shell bimetallic nanostructures on a titania surface. The nanostructural size and composition of the core–shell nanostructures and therefore their optical properties could be directly adjusted by the plasma process parameters and/or the postdeposition thermal treatment of the samples.

TiO2-based photocatalyst layers are still highly favored materials for photocatalysis on immobilized semiconductor electrodes because of their favorable electronic band positions, high corrosion stability, cost efficiency, and readily available titanium. Since chemical synthesis of nanocrystalline TiO2 layers from alkoxide precursors is usually complex and of low reproducibility, new methods are required to enable large-scale production of immobilized titania catalyst layers for practical applications. The synthesis of TiO2-layers on fluorine doped tin oxide (FTO) by means of a reactive sputtering process is reported here, with stable operation being implied by the means of a λ-sensor. Structural, electrochemical, and photocatalytic properties were investigated for different layer thicknesses and postdeposition annealing temperature of the deposited TiO2 by means of SEM, TEM, XRD, XPS, UV/vis spectroscopy, and a range of photochemical measurements including iE curves, acIS, IMVS and IMPS, and IPCE.

A polyallylamine coating was applied as a protective encapsulation to iridium dye sensitised TiO 2 catalyst layers by a plasma-enhanced chemical vapour deposition process. A significant enhancement of the incident-photon-to-current efficiencies of the polymer-confined dye/catalyst assembly was observed, with a strong dependence on the nominal thickness of the polymer-coating. An optimum thickness of the polyallylamine coating between 15 and 50 nm was obtained with regard to photoefficiency of the polymer-coated dye/TiO 2 catalyst in a neutral electrolyte. Results are discussed in terms of porosity and electrolyte permeability of the plasma polymer layer.

Recently, a new dual plasma-process to produce non noble metal catalysts for the oxygen reduction in proton exchange membrane fuel cells has been developed and catalytically active cobalt–polypyrrole-films have been produced. This paper shows a modification to this process, so that iron–polypyrrole is formed. The magnetron power as well as the process gases were varied. The structure of the compounds was then analyzed by energy-dispersive X-ray spectroscopy, X-ray diffraction, near edge X-ray absorption fine structure and extended X-ray absorption fine structure. It is shown that the oxidation of the compounds is suppressed when hydrogen or nitrogen is added to the process. Furthermore, cyclic voltammetry and rotating ring-disk electrode measurements were done to determine the electrochemical properties of the films. Only films produced in hydrogen or nitrogen containing gases show catalytic activity and it can be seen that the four-electron reduction mechanism is dominant.

A series of heteroleptic copper photosensitizers [(P _ P)Cu(N _ N(SO3Na)2)] + containing sulfonate anchor groups is described. In the presence of titanium dioxide they form composites, which are active photosensitizers in the light driven reduction of protons. Further stabilization of these systems is achieved by encapsulation within a plasma-polymerized allylamine (PPAAm) layer. The resulting PPAAm-CuPS-TiO2-composites exhibit a strong absorption in the visible region of the light. Photocatalytic hydrogen production is performed by using only nonnoble metals. In the presence of an iron reduction catalyst a maximum turnover number of 2452 is obtained.

In this contribution, the dual plasma process to produce catalytically active cobalt-polypyrrole-compounds is enhanced. This is done by adding nitrogen, hydrogen and oxygen to argon during the plasma process. The so-obtained compounds were analysed by EDX,XRD and NEXAFS to get information on the structural composition. Furthermore, CVmeasurements were done to determine the electrochemical properties of the films. It is shown that the catalytic activity increases slightly while the stability of the films can be greatly improved.

Photocatalysis for sustainable hydrogen production from water is becoming one of the core challenges for an efficient conversion of solar energy into a clean and renewable fuel, enabling the growth of a carbon-free hydrogen economy. In dye-sensitized TiO2, performances were obtained to be unstable over time due to weak covalent bonding of the molecule at the surface leading to detachment of the dye from the TiO2 surface and dye self-aggregation, with recombination of charge carriers at the dye/TiO2 interface being the second major factor for efficiency losses. Our strategy for improvement of the stability of the dye/TiO2 catalyst is the encapsulation of the assembly by a plasma-polymerized allylamine layer, providing a chemically and mechanically stable nanoconfinement of the dye in close proximity of the titania surface. The TiO2-layer was synthesized by a plasma-enhanced DC magnetron sputtering process on FTO substrates, resulting in homogeneous porous semiconductor layers. The stability of the PPAAm la...

New linear heterometallic Co3Li2 and Co4Li2 arrays have been assembled with the use of disiloxanediolate and silsesquioxane ligands. Treatment of anhydrous CoCl2 with in situ-prepared (Ph2SiOLi)2O afforded (thf)Co[Co{μ-(Ph2SiO)2O}{(μ-Cl)2Li(thf)2}]2 (5) as dark blue prisms in 73 % yield, while the analogous reaction of CoCl2 with in situ-prepared Cy7Si7O9(OLi)3 (Cy = cyclohexyl) gave royal blue [Co2(μ-Cy7Si7O12)(μ-OSiMe3)(μ-Cl){Li(thf)2}2]2 (6) in 68 % yield. Both of the new compounds have been structurally characterized by X-ray crystallography. Plasma treatment of 5 was found to activate the surface by creating –C–O, –C=O, and –COO functionalities. An initial study revealed promising formaldehyde adsorption properties for the plasma-treated material 5a.

The chemical structure of cobalt--polypyrrole -- produced by a dual plasma process -- is analysed by means of X-ray photoelectron spectroscopy (XPS), near edge X-ray absorption spectroscopy (NEXAFS), X-ray diffraction (XRD), energy-dispersive X-Ray spectroscopy (EDX) and extended x-ray absorption spectroscopy (EXAFS).It is shown that only nanoparticles of a size of 3\,nm with the low temperature crystal structure of cobalt are present within the compound. Besides that, cobalt--nitrogen and carbon--oxygen structures are observed. Furthermore, more and more cobalt--nitrogen structures are produced when increasing the magnetron power. Linking the information on the chemical structure to the results about the catalytic activity of the films -- which are presented in part I of this contribution -- it is concluded that the cobalt--nitrogen structures are the probable catalytically active sites. The cobalt--nitrogen bond length is calculated as 2.09\,\AA\ and the carbon--nitrogen bond length as 1.38\,\AA.

The influence of radio-frequency (RF) plasma treatment on the electrocatalytic properties of Fe-based catalysts with respect to oxygen and hydrogen peroxide reduction was investigated. The electrocatalytic activity was evaluated using cyclic voltammetry (CV) and rotating disk electrode (RDE) techniques. The chemical composition structure and surface morphology of the catalysts were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction analysis (XRD) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). A remarkable improvement in the electrocatalytic properties was achieved by N 2 -plasma treatment at 750 W.

In this work, the immobilization of two hydrolases on plasma-modified polypropylene carriers was investigated. Treating Ac- curel MP1001 with an oxygen plasma was found most suitable to increase the hydrophilicity and to allow for efficient immobi- lization. Thus, for lipase B from Candida antarctica and for an esterase from Pyrobaculum calidifontis esterase (PestE) a 5-fold and 14-fold increase, respectively, in immobilization yield resulted compared to untreated carrier. In contrast to the oxygen-modified support, modification of the polypropylene carrier with ammonia plasma showed no positive effect. Fur- thermore, it could be shown that immobilized PestE catalyzed enantioselective transesterification of α-phenylethanol in vinyl acetate, whereas the free enzyme showed no activity. Both hydrolases could be recycled five times without significant loss of activity.

Low temperature plasma (LTP) treatment of cobalt-tetramethoxyphenylporphyrin (CoTMPP) has been applied as a promising alternative method to the conventional heat treatment in order to attain highly active catalysts for the electroreduction of oxygen. In this contribution it is shown that CoTMPP can be completely transformed into a carbon matrix by adjusting adequate LTP parameters. The carbonisation process of CoTMPP is investigated at different operation conditionsby Raman and IRspectroscopy and compared with thestructural features of the heat-treated samples. As a result it appears that the LTP occurs via a different carbonisation process, which yields in a more homogeneously defined molecular carbon structure.

We synthesized chalcopyrite (CuFeS2) nanoparticles by methods involving laser ablation and electrical discharge in water. The nanoparticles obtained were exposed to an oxygen/argon plasma of a microwave discharge. The synthesized material was studied by photometry, x-ray diffraction (XRD), and energy dispersive x-ray elemental analysis (EDX), IR spectroscopy, and atomic force electron microscopy (AFM). We have established that the nanoparticles are morphologically stable relative to exposure to plasma fluxes of power ≤1 kW, and can be used as a model system to study processes of interaction between a plasma and minerals.

Copper-polypyrrole composites were successfully produced with a dual plasma process. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were used to characterise the structural properties. Topological and electrochemical investigations were also performed using atomic force and scanning electron microscopy (AFM, SEM) as well as cyclic voltammetry (CV) respectively. The results show that different composites were produced. When a low power was used, copper atoms bound to aromatic polymer structures were formed. Indications for the formation of electroactive copperpolypyrrole complexes are presented. Using higher power values, copper(I)oxide (ca. 3 nm) and copper nanoparticles (5-40 nm) embedded in a polymeric matrix were produced. Pulsing of the magnetron resulted in a modification of the chemical bonds within the samples.

The performance of pyrolyzed and plasma-treated non-precious catalysts for the oxygen reduction is discussed in the light of their application in microbial fuel cells. An Ar-radio frequency (RF) plasma treatment is applied to enhance the electrochemical activity of iron(II) phthalocyanine (FePc)-based catalysts. The electrochemical properties of the catalysts are analyzed by galvanodynamic linear sweep voltammetry and chronoamperometric experiments. Surface elemental analysis of the catalysts is examined by means of X-ray photoelectron spectroscopy (XPS). The influence of plasma power and treatment time on the elemental surface concentration and performance of the catalysts is investigated. The electrochemical activity, expressed in terms of the current density at 0 V vs. Ag/AgCl, is up to 40% higher for the plasma-treated samples than for pyrolyzed ones. It is found that optimal treatment time was 30 min and optimal plasma power was 150 W for the best electroactivity of FePc-based catalysts. From the results of XPS data, it is revealed that Ar-plasma treatment of the catalysts leads to an increase in the oxygen and nitrogen concentration on the catalysts surface. A correlation is found between the activity and surface concentration of oxygen and nitrogen on the catalysts’ surface.

Tungsten carbide nanopowder was prepared via pulsed discharge of bulk tungsten and graphite rods immersed in pure ethanol. The effect of discharge parameters on the characteristics of final products was investigated. Structural and morphological characterization of nanopowder was performed by means of X-ray diffraction analysis and transmission electron microscopy. In order to determine the feasibility of using synthesized material as an electrocatalyst, tungsten carbide nanopowder was tested for hydrogen evolution. A correlation was found between morphology of nanoparticles, their phase composition and electrocatalytic activity.

We report on the analysis of the composition and internal structure of SiO x layers deposited on powder particles by using HMDSO as monomer, different oxygen admixtures in argon, and a dielectric barrier surface discharge under atmospheric pressure. Composition and structure of the deposited layers with special regard to silicon, carbon, and hydrocarbon bonding were studied by FTIR and XPS measurements and compared with previous investigations from the literature. For correlation of the layer composition and the plasma gas phase we used mass spectrometric analysis of the exhaust gas. The stoichiometric ratios of the deposited layers are remarkably influenced by the Ar/O 2 ratio and the discharge conditions.

Plasma techniques have been extensively utilized in catalysis. Catalyst preparation using plasma treatment allows to improve dispersion, enhancing the catalyst performance and stability. In this paper, the low-pressure radio frequency (RF) discharge is shown as an efficient method to enhance the activity of cobalt tetramethoxyphenylporphyrin (CoTMPP)-based electrocatalyst for the reduction of hydrogen peroxide. It was found that a carbon-supported CoTMPP catalyst (20% CoTMPP/C) treated by plasma presents two-fold higher catalytic activity than catalyst prepared without plasma treatment. The influence of catalyst treatment on elemental surface and bulk concentration and performance of catalysts for hydrogen peroxide in a fuel cell was investigated.

In this work, we developed a methodology of plasma-enhanced preparation of CoTMPP (tetramethoxyphenylporphyrin)-based electrocatalysts. A series of CoTMPP-based electrocatalysts were deposited on the porous gas diffusion substrate (titanium fibre felt) using plasma-enhanced impregnation method. Impregnated 1.5 mg cm −2 CoTMPP/Ti catalysts were treated by dielectric barrier discharge (DBD) plasma in Ar or N 2 atmosphere. Additionally, the pretreatment methods were utilized to improve the adhesion of CoTMPP on the diffusion layer surface. The plasma pretreatment methods included the a-C:H-layers deposition followed by an Ar:O 2 radio frequency (RF) plasma functionalization. The latter approach led to the formation of specific oxygen surface groups that influenced the catalysts activity. Obtained catalysts were compared in terms of activity, stability and structure. The catalytic activity for hydrogen peroxide (H 2 O 2 ) reduction was tested in a proton exchange membrane fuel cell (PEMFC) using hydrogen peroxide on the cathode side. Surface elemental analysis and structure of catalysts were examined by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Our contribution shows the potential of a plasma treatment in the preparation of electrocatalysts for hydrogen peroxide reduction reaction in a PEMFC. Under the conditions of this study, improvement of the PEMFC performance up to 30% was achievable by a deposition of CoTMPP on the titanium diffusion substrate followed by plasma treatment. The large differences in catalytic activity of CoTMPP/Ti were observed, depending on the plasma treatment applied to the catalysts during their preparation.

The interaction of arcs with materials e.g. of the electrodes or of side walls are key issues of the functionality in many arc applications. An electrode configuration with a stable and reproducible arc operation as well as with optical access is preferable for the experimental analysis and fundamental study of such interactions.

Platinum-free electrocatalysts based on cobalt and polypyrrole were successfully produced with a dual plasma process and characterised for the oxygen reduction reaction by cyclic voltammetry (CV). The results show that composites with catalytic activity were obtained. Furthermore, by varying the plasma process parameters, the activity of the samples was changed. Structural properties were also investigated by means of energy dispersive X-Ray spectroscopy (EDX), to obtain the elemental contents, and Fourier transform infrared spectroscopy (FT-IR) to identify the chemical structure of the films. The results indicate that, with increasing magnetron power, more and more cobalt nitrogen bonds are formed. The formation of these complexes correlates with the increase in catalytic activity.

A new dual plasma coating process to produce platinum-free catalysts for the oxygen reduction reaction in a fuel cell is introduced. The catalysts thus produced were analysed with various methods. Electrochemical characterisation was carried out by cyclic voltammetry, rotating ring- and rotating ring-disk electrode. The surface porosity of the different catalysts thus obtained was characterised with the nitrogen gas adsorption technique and scanning electron microscopy was used to determine the growth mechanisms of the films. It is shown that catalytically active compounds can be produced with this dual plasma process. Furthermore, the catalytic activity can be varied significantly by changing the plasma process parameters. The amount of H$_2$O$_2$ produced was calculated and shows that a 2 electron mechanism is predominant. The plasma coating mechanism does not significantly change the surface BET area and pore size distribution of the carbon support used. Furthermore, scanning electron microscopy pictures of the produced films are presented and show the preference of columnar growth mechanisms. By using different carbons as the support it is shown that there is a strong dependence of the catalytic activity that is probably related to the chemical properties of the carbon.

Visible-light-driven photocatalysis is currently attracting a great deal of attention because of its potential application in solar water splitting. However, the development of efficient and durable catalyst systems is still a challenging problem. In Ru dye-sensitised TiO(2) nanopowders, catalyst performances are found to decline as a result of poor bonding of the dye molecule to the TiO(2) surface and subsequent detachment and self-aggregation of the dye. Our strategy to improve the stability of the dye-TiO(2) interface is the encapsulation of the dye/TiO(2) assembly in an amino-group-containing polyallylamine layer anchored to TiO(2). A low-pressure pulsed microwave discharge plasma polymerization process was employed to coat a commercial anatase nanopowder with a thin polyallylamine layer to nanoconfine the adsorbed dye molecules. Electron microscopy and UV/Vis spectroscopy was carried out to characterise the resulting encapsulated nanostructures. The long-term stability of the new nanomaterial as the photoactive component of a water reduction catalyst system for H(2) evolution investigated in a slurry reactor under visible-light irradiation showed stable evolution rates over a period of several days.

Proton exchange membrane fuel cells (PEMFC) lag behind the theoretical efficiency because of kinetic and mass transfer problems of the catalyst layer, especially the oxygen reduction catalyst layer and the methanol oxidation catalyst layer. In these fields almost all research in catalysts and catalyst layers are done on Pt nanoparticles and the perfect composition of Nafion to Pt catalyst on the corresponding substrate, for example carbon nanoparticles. The typical catalyst layer for the oxygen reduction reaction has a thickness between 5 µm and 25 µm. For the methanol oxidation reaction the thickness is even higher. The kinetic barriers of the oxygen reduction and the methanol oxidation, oxygen and methanol diffusion, proton conductivity barriers and potential distribution across the catalyst layer hinder the Pt efficiency which is, at the end, only 10-20%.[1] Pt usage has to be minimized since it will be responsible for over 50% of the system costs in PEMFC[2]. These problems can be circumvented using mesoporous Pt skeleton layers where H+ probably migrate across the surface and/or diffuse in H2O, like in the nanostructured thin films (NSTF) [3]. Additionally in our approach no carbon support and Nafion is needed – it is supportless and ionomerless. Pt skeleton was prepared by a dual-magnetron plasma-synthesis. The pore and bone scaling can be controlled by system parameters as pressure, deposition time, temperature and power. For fundamental understanding of Pt skeleton it is necessary to investigate the influence of the solid to pore ratio on the performance. In this work a Pt skeleton was synthesized by alternated sputtering of Pt and Co on gas diffusion layers and glassy carbon. The base metal was subsequently dissolved by an electrochemical treatment under acidic conditions, with the Pt skeleton remaining on the substrate. The remaining catalyst layer has a thickness of approximately 200 nm. Cyclic voltammetry and oxygen reduction activity tests gave information on the global behaviour of the electrodes. Scanning Electron Microscopy was employed to investigate pore and bone morphology. It was possible to produce a Pt skeleton with different pore sizes and bone diameter. Furthermore Pt can be tuned by the remaining Co in the catalyst. The Cobalt remains in the catalyst layer which was tested also for different system parameters. The remaining Co was investigated by the d-band shift of the catalysts by XPS and the corresponding EDX atomic ratios before and after electrochemical testing. The new approach of mesoporous Pt skeleton synthesized by a new plasma process is a revolution in catalyst layer architecture. The typical catalyst layer thickness can be reduced by a factor of 100 and there is no need for a corroding support. Furthermore Nafion as proton carrier can be excluded and therefore limiting anion adsorption can be avoided. Our new approach could also be used for air electrodes or electrolyzers as the Power to Gas technology is going forward. Figure 1: Scheme of the proposed reaction mechanism in the oxygen reduction reaction of Pt skeleton (left) and a SEM picture of Pt skeleton (right) [1] M. Eikerling, A.S. Ioselevich, A. a. Kornyshev, How good are the Electrodes we use in PEFC?, Fuel Cells. 4 (2004) 131–140. doi:10.1002/fuce.200400029. [2] U. Eberle, B. Müller, R. von Helmolt, Fuel cell electric vehicles and hydrogen infrastructure: status 2012, Energy Environ. Sci. 5 (2012) 8780. doi:10.1039/c2ee22596d. [3] M.K. Debe, Tutorial on the Fundamental Characteristics and Practical Properties of Nanostructured Thin Film (NSTF) Catalysts, J. Electrochem. Soc. 160 (2013) F522–F534. doi:10.1149/2.049306jes. Figure 1

In Proton Exchange Membrane (PEM) Electrolysis bipolar plates have to be more corrosion resistant than bipolar plates in PEM Fuel Cells. Several materials have been evaluated as cost-efficient material in PEM Electrolyzers. Since the electrochemical conditions in PEM Electrolyzers are quite harsh, cost-efficient materials like stainless steel or graphite composites are not stable. Coating the material with corrosion resistant material by magnetron sputtering is one possibility to enhance the stability. Gago et al.[1] have been coating stainless steel for example with Ti by vacuum plasma spraying. However, Ti is only useable if the oxidation potential is not too high, otherwise it will form an insulating TiO2 layer. Tantal has good corrosion protective characteristics and is not forming an insulating layer.[2] We developed a plasma process to deposit protective coatings on graphite composite bipolar plates. Therefore we used unbalanced magnetron sputtering of Ti and Ta. A new magnetron sputtering process was applied to keep the temperature of the graphite composites constant. Furthermore a combined plasma-process was used to enhance the stability of the deposited layer by activating the graphite composite. The Ti and Ta coatings were tested in a heated (T = 353 K) electrochemical cell amperometric at 2 V vs. RHE and by cyclic voltammetry in oxygen saturated 0.5 M H2SO4. We figured out the layer quality with the 4-Point Probe before and after each experiment. Furthermore we evaluated the film characteristics by microscope (SEM, light microscope), XRD and XPS. We could demonstrate that the coating is protecting the graphite composite as bipolar plate material in harsh electrochemical environment which was choosen close to real conditions in PEM Electrolyzers. Thereby it should be possible to lower the cost of bipolar plates in PEM electrolyzers substantial. [1] A. Gago, A. Ansar, N. Wagner, J. Arnold, K.A. Friedrich, Titanium coatings thermal spraying bipolar plates PEM electrolyzer, in: 64th Annu. Meet. Int. Soc. Electrochem., 2013. [2] O.E. Kongstein, N. Guillet, A. Ødegård, Rapport technique DEHT-DR-10/051, 2010.