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Organocatalysis with chiral iodoarenes has emerged as a powerful approach for performing enantioselective transformations, however, suffering from the need to utilize stoichiometric amounts of peroxy acids or similar high energy oxidants. Electrosynthesis enables eliminating stoichiometric redox reagents by replacing them with electric stimuli. In this context, an electrochemically-promoted variant of the chiral iodoarene-catalyzed asymmetric diacetoxylation of styrenes was evaluated. The screening of reaction parameters established a set of conditions under which, for the first time, an enantioselective electrochemical oxidation mediated by a chiral iodoarene achieving a catalytic turnover has been accomplished. The reaction was applied for the synthesis of an array of products in 15-60% yields and 0-84% ee. The modest efficiency of the electrocatalysis was traced to a partial direct oxidation of styrene substrates leading to racemic products and undesired dimeric side-products. Cyclic voltammetry measurements demonstrated that such outcome originates from a somewhat difficult electrochemical oxidation of the applied iodoarene catalyst. Present work provides important insights and implications for the design of more efficient electrocatalytic systems employing chiral iodoarenes as mediators.

The structural and chemical modification of TiO2 nanotubes (NTs) by the deposition of a well-controlled Au deposit was investigated using a combination of X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Scanning Transmission Electron Microscopy (STEM), Raman measurements, UV-Vis spectroscopy and photoelectrochemical investigations. The fabrication of the materials focused on two important factors: the deposition of Au nanoparticles (NPs) in UHV (ultra high vacuum) conditions (1–2 × 10−8 mbar) on TiO2 nanotubes (NTs) having a diameter of ∼110 nm, and modifying the electronic interaction between the TiO2 NTs and Au nanoparticles (NPs) with an average diameter of about 5 nm through the synergistic effects of SMSI (Strong Metal Support Interaction) and LSPR (Local Surface Plasmon Resonance). Due to the formation of unique places in the form of “hot spots”, the proposed nanostructures proved to be photoactive in the UV-Vis range, where a characteristic gold plasmonic peak was observed at a wavelength of 580 nm. The photocurrent density of Au deposited TiO2 NTs annealed at 650 °C was found to be much greater (14.7 μA cm−2) than the corresponding value (∼0.2 μA cm−2) for nanotubes in the as-received state. The IPCE (incident photon current efficiency) spectral evidence also indicates an enhancement of the photoconversion of TiO2 NTs due to Au NP deposition without any significant change in the band gap energy of the titanium dioxide (Eg ∼3.0 eV). This suggests that a plasmon-induced resonant energy transfer (PRET) was the dominant effect responsible for the photoactivity of the obtained materials.

The oxidative dearomatization of phenols with the addition of nucleophiles to the aromatic ring induced by hypervalent iodine(III) reagents and catalysts has emerged as a highly useful synthetic approach. However, experimental mechanistic studies of this important process have been extremely scarce. In this report, we describe systematic investigations of the dearomatizing hydroxylation of phenols using an array of experimental techniques. Kinetics, EPR spectroscopy, and reactions with radical probes demonstrate that the transformation proceeds by a radical-chain mechanism, with a phenoxyl radical being the key chain-carrying intermediate. Moreover, UV and NMR spectroscopy, high-resolution mass spectrometry, and cyclic voltammetry show that before reacting with the phenoxyl radical, the water molecule becomes activated by the interaction with the iodine(III) center, causing the Umpolung of this formally nucleophilic substrate. The radical-chain mechanism allows the rationalization of all existing observations regarding the iodine(III)-promoted oxidative dearomatization of phenols.

The CuO@CuFe

Novel materials, architectures, geometries are crucial for achieving the progress in science in general. Therefore, heterojunction engineering, which enables more versatile and higher performance systems than single components, has emerged as a means of tailoring the optoelectronic properties of photoelectrodes. However, constructing effective and stable hybrid semiconductor heterojunctions is a challenging task under the strict requirements of band alignment, vacancy characteristics, and interface properties. In this presentation, we will demonstrate the enhancement of photoelectrochemical (PEC) reduction of CO2 to methanol, by a novel approach relying on modeling the Fermi level in a multi-interface architecture. The excellent PEC CO2 reduction activity has been attributed to the formation of a high-performance, energetically aligned multi-interface system of CuO/Cu2O||rGO|h-WO3|rGO (rGO = reduced graphene oxide layer). The overall performance of this hybrid system strongly depended on the number of oxygen groups in rGO and the structural properties of rGO. Furthermore, to construct an effective PEC system, numerous postsynthetic treatments were explored for their practicality and usefulness. The results presented herein clearly showed that the best performance toward the CO2 photoreduction currents of 3 mA/cm2 at 0.00.1 V versus RHE (more than double that of the CuO/Cu2O system) had been reached for the semiconductor architecture containing two inter-layers of rGO. The role of those layers in the overall system performance will be an objective of the presentation.

Heterojunction engineering enables more versatile and higher-performance systems than single components. In parallel with heterojunction engineering, defect engineering has emerged as a means of tailoring the optoelectronic properties of photoelectrodes. However, constructing effective, visible-light responding, and stable hybrid semiconductor heterojunctions is a challenging task under the strict requirements of band alignment, vacancy characteristics, and interface properties. In this study, the photoelectrochemical (PEC) reduction of CO 2 to methanol is augmented by a novel approach explored by modeling the Fermi level in a multi-interface architecture.

In the present work, we investigated the behavior of titanium dioxide photocatalysts decorated with plasmonic metal – gold and silver – nanoparicles (NPs) for the photooxidation of small organic molecules. The TiO2 samples were large surface area thin film electrodes formed either by thermal oxidation of the Ti metal (for the rutile films) or deposited on the same substrate by a sol-gel method (for the anatase films). The TiO2 films were subsequently decorated with Au nanostructures using either photodeposition or vacuum sputtering. The Ag nanostructures were formed on TiO2 by electrodeposition. Although both the Au-TiO2 and the Ag-TiO2 films yielded photoanodic currents under illumination with visible wavelengths, consistent with the resonant frequencies of plasmonic metal NPs, prolonged polarization resulted in the drastic drop of photoactivity. Such deactivation, that did not affect the range of near-UV wavelengths absorbed by the pristine TiO2, has been assigned to the surface oxidation of the plasmonic NPs progressively blocking the charge regeneration within the metal nanoparticles. These results raise questions in regard to the use of Au-TiO2 and Ag-TiO2 photocatalysts for sunlight-driven photodegradation of organic contaminants in water.

Further advancement in sunlight-driven splitting of water as a means of producing hydrogen and oxygen is mainly hampered by the availability of easy-to-prepare, inexpensive n-type semiconductor mat...

In the recent years, the dearomatization of phenols with the addition of nucleophiles to the aromatic ring, induced by hypervalent iodine(III) reagents and catalysts, has emerged as a highly useful synthetic approach. However, experimental mechanistic studies of this important process have been extremely scarce. As a result, the mechanism of the reaction remained elusive and as of today there exist as many as three distinct mechanistic proposals. In this report, we describe systematic investigations of the dearomatizing hydroxylation of phenols using an array of experimental techniques. Kinetics, EPR spectroscopy, and reactions with radical probes demonstrate that all the previously suggested mechanisms are incorrect, and that the transformation in fact proceeds via a radical-chain mechanism, with the aryloxyl radical being the key chain-carrying intermediate. Moreover, UV and NMR spectroscopy, high-resolution mass spectrometry, and cyclic voltammetry show that before reacting with the aryloxyl radical, water molecule becomes activated by the interaction with the iodine(III) center, causing this formally nucleophilic substrate to act as an electrophile. The C–O bond formation is identified as the rate-determining step of the reaction. This step generates the dearomatized product and an iodanyl(II) species, which is the second chain-carrying radical. The radical-chain mechanism emerging from our investigations allows to rationalize all other existing observations regarding the iodine(III)-promoted oxidative dearomatization of phenols.

Photoelectrochemical reduction of CO 2 is explored here with respect to the possible production of simple organic fuels. While the photoelectrochemical system is based on p -type Cu 2 O semiconductor, special attention has been paid to its stabilization, intentional modification and fabrication, as well as to optimization of experimental conditions permitting control and diversification of the CO 2 reduction products. Utilization of the mixed oxides photoelectrochemical system consisting of the electrodeposited, onto transparent conductive oxide (TCO) coated glass support, Cu 2 O catalyst and next coupled to non-stoichiometric TiO 2 , acting as a charge transfer enhancing layer. Such a heterojunction allows, from one side, increase density of charge carries in the conduction band of the photocathode and, on the other side, improve conductivity of the whole system. Moreover, the outer-most over-layer of Nafion is expected to facilitate attraction of CO 2 (dissolved in the sodium sulfate electrolyte) at the photoelectrochemically active mixed-metal-oxides interface. Consequently, the overall photoelectrochemical efficiency is improved, and the cathodic photocurrent (related to the CO 2 -reduction) of ca. 1.2 mA cm−2 (at 0.1 V vs. RHE). The reported hierarchical (layered mixed-oxide) system consisting of copper(I) oxide and titania over-layer (covered with the Nafion outer-most film) exhibits remarkable stability with time.

Growing interest in composite plasmonic-metal/semiconductor photocatalysts is motivated by the ability of plasmonic nanostructures to capture light, most particularly at their resonance frequencies at which they exhibit high absorption and scattering cross-sections. In the cases when plasmon resonance frequency overlaps absorption spectrum of the semiconductor, large electric field enhancement near the surface of the metal nanostructure leads to increased charge carrier generation in the nearby semiconductor (plasmonic near-field effect). Another, largely evoked, kind of interaction is the spectral sensitization of a semiconductor to longer wavelengths absorbed only by the plasmonic nanostructure. In such a process, hot electrons generated in the metal nanostructure via the decay of optically excited plasmons are transferred over the Schottky barrier to the nearby semiconductor resulting in extra band-gap photoactivity. Several examples pertaining to each of these interactions will be discussed. While interest in composite plasmonic-metal/semiconductor photocatalysts is relatively recent, there has been substantial earlier work on plasmon-mediated photoelectrochemistry on a typical plasmonic metal-silver. It is shown that roughening of the silver electrode surface leads, for example, to largely enhanced cathodic CO 2 reduction photocurrents observed under illumination with UV-visible wavelengths that coincide with plasmon resonance frequencies in silver.

Hybrid heterostrures provide a versatile and largely enhanced systems in comparison to their single components. However, construction of effective visible-light responding and stable hybrid heterojunction based photoelectrodes remains a challenge due to stricte requirements regarding band alignment in such constructions. Therefore implementation of a conductive mid-layer of reduced graphene oxide (RGO) might be a crucial factor in band structure engineering. Herein we demonstrate the formation of an outperforming hybrid heterojunction photocatalyst containing diversified synthetic approaches RGO and thus allowing to engineer the Fermi level position within the working architecture. Shifting the position of the Fermi level makes possible to increase the size of the depletion layer and PEC efficiency of the entire system increases.

This paper aims to analyze process of Variable Reluctance Generator stator core radial vibrations development. Frequency structure of generated vibrations strongly depends on rotor speed, generator load and adopted technique of phase current limitations. Qualitative change of vibration frequency structure could be associated with particular state of operation of mechanically coupled system (generator and turbine). Significant increase of rotor angular velocity variations associated with rotating mass (coupled rotors) free oscillations is correlated with maximum amplitude of developed vibrations acceleration. Interesting phenomenon is appearance of vibrations that present chaotic behavior.

Nanostructured WO3 photoanodes with crystallographic orientation along the [001] direction were fabricated via doctor blading nanoparticles synthesized through a microwave-assisted nonaqueous sol–gel route. Monoclinic WO3 platelets with a size ranging from 20 to 40 nm and a thickness of 3 nm were obtained after a short reaction time of 10 minutes under microwave irradiation. The films consisted of a porous network of nanoparticles and their photoelectrochemical activity was tested. After cathodic polarization of the photoanodes in the dark which led to a significant increase of 65% of the photocurrent, the films exhibited initially a maximum photocurrent of 2.7 mA cm−2 at 1 V vs. reversible hydrogen electrode (RHE) in 3 M H2SO4 under simulated AM 1.5 G illumination (100 mW cm−2) comparable to the best photocurrents reported for WO3 photoanodes. However oxygen evolution measurements showed that the faradaic efficiency dropped after the cathodic polarization and other products than O2 might be formed. In comparison to the chemical solution growth of films from molecular precursors, the use of preformed nanoparticles in the form of powders is not only more robust and easier to up-scale, but also offers many opportunities to improve the photoelectrochemical performance by tailoring the nanoparticle size, the shape, and their arrangement on the substrate.

Tungsten trioxide (WO3) is one of a few stable semiconductor materials liable to produce solar fuel by photoelectrochemical water splitting. To enhance its visible light conversion efficiency, we incorporated plasmonic gold nanoparticles (Au NPs) derivatized with polyoxometalate (H3PMo12O40) species into WO3. The combined plasmonic and catalytic effect of Au NPs anchored to the WO3 surface resulted in a large increase of water photooxidation currents. Shielding the Au NPs with polyoxometalates appears to be an effective means to avoid formation of recombination centers at the photoanode surface.

Vibrations of high speed SRM design focused on possible highest efficiency and low torque ripples both in motoring and generating mode of operation are investigated. The main constructional nodes that are source of vibrations are identified based on comparison of time sequences of motor frame displacement acceleration with total and phase motor current. Vibration analysis is the second stage of design process that suggest possible additional changes in stator and rotor geometry and controller operation that minimizes detrimental vibro-acoustic phenomenon.

The results of four phase switched reluctance motor tests were presented in this paper. Torque versus speed characteristics were executed for different control parameters. The energy converter designed to this motor allows to control phase current and switching angles independently. The experimental results show that the shape of the mechanical characteristics heavily depends of the switching angles and maximum phase current. It has been found through tests, that efficiency characteristics of the drive can be improved by the right adjustment of the switching angles, even in the low load conditions.

In the present study, we utilize phosphomolybdate (PMo12O40 3-) modified gold nanoparticle (diameters, 30-40 nm) deposits on mesoporous tungsten oxide photoanodes to study plasmon-assisted photoelectrochemical water splitting. Such n-type semiconducting oxide as WO3 (band gap, 2.5 eV) suffers from inadequate solar light absorption and, therefore, there is a need to use of a thin plasmon active layer of nanostructured Au of proper architecture to enhance the interfacial light trapping and conversion. A remarkable increase in the solar energy conversion efficiency as well as in the photooxidation current (oxygen evolution) are believed to be induced by the plasmonic excitation of Au nanoparticles occurring within WO3 absorption range. The polyoxometallate (PMo12O40 3-) monolayer-type nanostructures may play electrocatalytic role, improve charge distribution, in addition to the stabilization effect. In the other study, the PMo12O40 3- modified Au nanoparticles, when deposited on step-bunched silicon Si(111) surface have also acted as electrocatalytic centers during photoelectrochemically induced reduction of carbon oxide (IV). The applicability of phosphomolybdate-protected gold nanoparticles to create porous matrix for photoelectrochemically assisted reduction of carbon dioxide is even more pronounced when the system is further decorated with copper. We also present the result of decorating multi-walled carbon nanotubes with gold and copper nanoparticles (by chemical reduction method and through electrodeposition) acting as catalytic systems active towards CO2 electroreduction under voltammetric conditions. Carbon nanotubes have been chemically modified here with surface oxygen complexes using HNO3 and H3PMo12O40 solutions.

Solar energy conversion with high yield and cost-effective ratio requires use of materials which are easily available, stable within the time and flexible in structure in order to allow improvements in their intrinsic and surface properties. A class of such materials are perovskites with ABO3 structure or kesterites. The basic structure of ABO3, has a high structural tolerance factor and can be maintained with a wide variety of constituent elements. As a result, the composition-property relationship can be systematically investigated while keeping the same crystal structure. Also, due to the exceptional stability of the structure, the valency, stoichiometry, and vacancy of perovskite compounds can be varied widely in order to tune optical, electrical and catalytic properties. Therefore, the challenge is to couple the synthetic approach with an expected outcome resulting from the theoretical calculations. In this presentation we will show the study on quaternary Ln1-xNixTiO3 that revealed the optical and electronic properties might be affected by varying La content in the matrix under employment of a reductive atmosphere of H2. This constitutes a unique and advantageous feature for its use in solar energy conversion. Understanding the effect of La doping and Ni segregation occurring under the reductive atmosphere on the photoelectrochemical properties of the La1-xNixTiO3 will generate new set of knowledge while providing a facile route to tune photon absorption and charge transport properties. A similar study will be presented for kesterite Cu2ZnSnS4. The questions which will be undertaken are: does La doping favourably affect the electron-hole separation in addition to the enhancement of photon absorption?; how do oxygen vacancies created by ion doping and reduction in hydrogen affect the charge transport properties?; can Ni segregation affect the catalytic property of the Ln1-xNixTiO3 surface?. The same questions will be applied to kesterite based PEC system upon ion doping and applied atmosphere. We will try to answer these questions through use transient absorption spectroscopy approach allowing to follow changes in charge carrier dynamics from the sub nanoseconds up to seconds timescales upon introduction of any variable to the system.

Solar energy conversion to different types of energy which might be subsequently released by divers’ ways remains an unsaturated need, since the global demand for energy is continuously growing and will continue to rise. However, currently the field of renewable energy suffers from lack of an ideal material able to drive conversion of the solar energy with high efficiency and being stable enough to provide a long-term productivity. Therefore, multi-directional efforts including development of new materials and catalysts, incorporation of plasmonic nanostructures or creation of low-level sub- stoichiometry through different approaches including combination of intrinsic and surface modifications are continuously undertaken and devoted to minimisation of the required bias voltage, improvement of light capture or charge transport properties. Our recent achievements regrading employment of different in structure polyoxometalates as catalysts, sub-stochiometric semiconducting oxides, newly designed and engineered crystal structures in solar driven arrangements as well as their performance for photo induced processes such as oxidation or reduction will be presented and discussed in detail. Besides the extensive characterization of the above-mentioned systems, the kinetic assessment of the transient absorption phenomena will be approached. Use of transient absorption spectroscopy to study charge carrier behaviour in semiconductors-based systems allows to relate a photoelectrode architecture to the charge carrier origin, separation, collection, trapping, lifetime and therefore final efficiency. Presentation and comparison of the charge carrier dynamics occurring in semiconducting systems: bare, modified as well as mixed oxides, are particularly useful in clarifying the observed differences in in their photoelectrochemical performance.

Solar-to-hydrogen photoelectrochemical cells (PECs) have been proposed as a means of converting sunlight into H2 fuel. However, in traditional PECs, the oxygen evolution reaction and the hydrogen evolution reaction are coupled, and so the rate of both of these is limited by the photocurrents that can be generated from the solar flux. This in turn leads to slow rates of gas evolution that favor crossover of H2 into the O2 stream and vice versa, even through ostensibly impermeable membranes such as Nafion. Herein, we show that the use of the electron-coupled-proton buffer (ECPB) H3PMo12O40 allows solar-driven O2 evolution from water to proceed at rates of over 1 mA cm(-2) on WO3 photoanodes without the need for any additional electrochemical bias. No H2 is produced in the PEC, and instead H3PMo12O40 is reduced to H5PMo12O40. If the reduced ECPB is subjected to a separate electrochemical reoxidation, then H2 is produced with full overall Faradaic efficiency.

Silver nanoparticles deposited on FTO conductive glass substrate have been incorporated within n-type WO3 films formed by a sol-gel method. A large enhancement in water splitting photocurrents under AM1.5 visible light irradiation for the WO3 photoanode with embedded Ag nanoparticles was observed. The ability of Ag nanoparticle arrays on FTO to generate localized surface plasmons under visible wavelengths in the presence of the WO3 over-layer was confirmed by scanning near-field optical microscopy (SNOM) measurements.

The AFM scratching technique was applied to determine the absolute thickness of the electrodeposited poly o -methoxyaniline films in dependence of an anion type ( SO 4 2 - ,Cl − , ClO 4 - ) and a monomer concentration (0.01–0.06 M). The measured thickness range varies from 10 to 2000 nm in dependence on the anion identity and concentration. The AFM data are compared with the thickness calculated from the oxidation charge coupled to the reaction of leucoemeraldine to emeraldine form of the polymer. The proper way to determine capacitance charge is discussed. The observed excess of charge under CV dependence is explained by the charge required for cross linking of the polymeric chains. The anionic influence on the thickness of electrodeposited films is explained by influence of an anion on film morphology, rather than dependence on the anionic radiuses. The results point out that the determination of the number of electrons taking part in the process studied on the basis of the integration of the current–potential (CV), hence the mechanism of the polymerization and oxidation of the polymeric films might be easily misleading only because the capacitance charge of the polymer cannot be appropriate determined.

Eutectic materials have potential as photoactive materials, due to their multiphase character (various available photoactive component phases and multiple band gap energies) and high crystallinity....

The proper deposition bath composition for electrochemical synthesis of the CdSe deposit in the hexagonal structure of the right elemental stoichiometry, and photoreacting as an n-type semiconductor which can be used as a stable photoanode is investigated. The deposits were prepared by a cyclic potentiodynamic technique and the concentration of Cd2+ and SeO32− in the deposition baths varied from 10−4 M to 0.1 M, and from 10−5 M to 10−3 M, respectively. The electrochemical, the X-ray diffraction (EDS and XRD), and the photoactivity studies of a number of deposits have shown that application of the solution composition following Cd:Se = 5:1 results in deposition of the stoichiometric CdSe. The detected ratio of reagents is explained on the base of reaction mechanism and necessary excess of cadmium ions preventing CdSe deposit dissolution. The procedure of CdSe electrosynthesis was developed to yield of a direct semiconductor in the hexagonal structure. The necessity for cadmium cations excess is explained on the basis of the mixed electrochemical/chemical deposition mechanism.

Process of CO2 reduction requires substantial decrease of the energy barriers. Consequently, one of the promising way to approach this problem is using use of metal nanoparticles to accelerate electrons and make them more electronegative at the end of this process. Better understanding of the photo-induced phenomena enables to improve design & construction of semiconductor architectures governing the efficiency of CO2 reduction and its selectivity. The objective of this presentation will rely onto use of semiconductor photocathode with co-assembly of plasmonic and catalytic metal nanoparticles, such as silver or gold with other metal electrocatalysts which decrease the energy barriers of the CO2 reduction process through interaction of photo-excited surface plasmon states with adsorbed reaction intermediates. The significance to investigate reduction of CO2 with gold, silver and copper nanoparticles, enhanced by the extra activation of the process provided by the illuminated, incorporated plasmonic metallic nanostructures is supported by the occurrence of the photo-emission process associated with the decay of photo-excited surface plasmons. The occurrence, and contribution of this process to the overall efficiency of the CO2 reduction process as well as its impact on the distribution of the products will be investigated and discussed in detail. Moreover, the tradeoff between CO2 and water reduction will be continuously investigated and discussed in view of choice of the best metal-based catalyst designed for high efficiency and best selectivity CO2 reduction process.

Photoelectrochemical applications of semiconducting metal oxides are continuously growing and gaining a considerable interest in view of enhanced production of renewable energy. However, overcoming intrinsic limitations of well-known and recognized towards specific action semiconducting oxides such as iron oxide, titanium oxide, tungsten oxide or copper oxide requires development of new nanoarchitectures. Given the band edges positions are not always suitable for a desired solar driven process, of primary importance is to enhance the intrinsic properties of the building materials and couple them with a catalytic modification of the surface. Therefore, efforts including development of new hetero-nanostructures and their implementation to the different type of junctions employed in solar arrangements, are continuously devoted to minimization of the required bias voltage, improvement of light capture or charge separation and collection. Recently, these approaches allowed to develop a highly active catalytic system consisting of a mesoporous semiconducting metal oxide (tungsten trioxide, titanium dioxide or iron oxide) and attached thereto polyoxometalate based WOC. The stable and reproducible water splitting photocurrents reached 4.5 mA cm-2 for WO3 based working system and were attained at standard conditions. In this scenario, incorporated in small amount polyoxometalates act as highly effective molecular OER catalysts leading to very large enhancement of water oxidation photocurrents [1]. These findings have also been transferred to other semiconducting systems relying onto engineered low sub-stoichiometric disorder in TiO2 or hexagonal WO3 conjugated to copper (I) oxide, enhanced and stabilized by the presence of heterojunction [2]. A special attention will be paid to their stabilization, intentional modification, as well as optimization of experimental conditions, permitting control and diversification of the reaction products. [1] M. Sarnowska, K. Bienkowski, P. J. Barczuk, R. Solarska, J. Augustynski, Adv. Energy Mater. (2016), 1600526 [2] E. Szaniawska, K. Bienkowski, I. Rutkowska, P. Kulesza, R. Solarska, Cat. Today (2017) doi.org/10.1016/j.cattod.2017.05.099

The in situ atomic force microscopy and the electrochemical studies on electropolymerization of the o -methoxyaniline in the 0.0–0.8 V versus NHE range of the electrode potential are described. It is proved that in the 0.0–0.3 V versus NHE a redox process takes place, resulting in the formation of poly( o -methoxyaniline) in its reduced form, leucoemeraldine. The different morphologies are exhibited by poly( o -methoxyaniline) under different polymerization conditions. The microscopic results show that with the increase of the monomer concentration in the bulk of electrolyte solution the globular morphology, related to the coil like molecular structure, is replaced by the fibrilar one, related to the opened-up, more conductive extended coil structure. It is shown that oxidation of a leucoemeraldine state of polymer to its emeraldine state results in the change of the morphology from the chain like structure to the massive fibrilar like structure. The reduction of oxidized polymer results in its irreversible fragmentation.

Sequential doping of polyaniline base in the oxidation state of emeraldine (abbreviated as PANI) first with iron(III) chloride and then treated with hexafluoroacetylacetone (HFAA) is described. The results obtained by using a combination of spectroscopic techniques (UV–vis–NIR, mass spectroscopy, Mossbauer effect spectroscopy, EPR) unequivocally show that complete Lewis acid-type complexation of PANI with FeCl 3 occurs only in the solid state, i.e. after removal of the solvent. In the solution an equilibrium is established between PANI complexed with FeCl 3 and FeCl 3 complexed with nitromethane. The addition of HFAA to the solution, being in equilibrium, transforms Lewis acid doped PANI into mixed doped polymer, which upon casting and solvent removal gives a solid material of a general formula: PANI(FeCl 3 ) x (HCl) y (HFAA) z . In this compound FeCl 3 is complexed with amine nitrogens, imine nitrogens are protonated with HCl. HFAA, dispersed in the polymer matrix, serves as a plasticizer. The determined chemical constitution is a direct consequence of the reaction of HFAA with FeCl 3 complexed on PANI imine sites to give HCl and iron(III) hexafluoroacetylacetonate. The former protonates the imine sites whereas the latter is removed from the system by extended pumping as proved by mass spectroscopy. Mossbauer spectra unequivocally show that FeCl 3 complexed on amine sites remains intact. Films of PANI(FeCl 3 ) x (HCl) y (HFAA) z show room temperature conductivity of ca. 3 × 10 −3 S cm −1 and improved mechanical properties as compared with PANI complexed solely with FeCl 3 due to HFAA plasticizing effects.

Photo-electro-reduction of CO2 is continuously gaining a considerable interest in view of possible production of carbon-based energy carriers. Given the periodic availability of solar light, of primary importance is to orient the CO2 conversion versus formation of easily storable fuels such as, e.g. methanol or ethanol. Thus, it is important to diversify the CO2 reduction products not only by the applied potential but by careful optimisation of the working system. A default approach, consists in using p-type semiconductors as a main component of the CO2-reduction cathodes. However, the intrinsic drawback of p-type semiconductor photo-cathodes lies in low electron density in the CB and, as generally observed, the lack of catalytic properties towards CO2 reduction. Thus, in an attempt to increase the conduction band electron population, we will present herein a build-up hybrid photo-electrodes including p-type - n-type semiconductors junctions. An additional advantage of creating such p-type – n-type semiconductor heterojunction is protection of the p-type component against photocorrosion induced by largely negative potentials that offers, at the same time, the possibility to enlarge the choice of employed p-type semiconductors to relatively unstable ones. The requirements for the n-type semiconductors are fulfilled by several metal oxides such as TiO2 or SrTiO3, or KTaO3. Apart the role of heterojunction in CO2 activation, we will also point out a particular aspect of using a model system involving Au NPs of different sizes deposited on a TiO2/Ti substrate by examining the electro-reduction of carbon monoxide. This reaction appears as being the crucial, kinetically difficult, step in the electro-reduction of CO2 to alcohols and hydrocarbons. Recognition and understanding of an individual process might already give a picture of a whole system.

There has been growing recent interest in the development of electrochemical and photoelectrochemical approaches toward effective fixation (reduction) of carbon dioxide. Having in mind a fact that the linear O=C=O molecule is very stable, the CO2 electroreduction requires large overpotentials. In other words, utilization of renewable energy to convert carbon dioxide and water into fuels would require selective CO2-reduction catalysts or efficient and robust semiconductors. There is a need to design unique nano-architectures consisting of the CO2 photocatalyst/semiconductor stabilized with the outer protective layer. Our study utilizes copper(I) oxide either stabilized with nanostructured titania or ultra-thin films of certain, conducting or redox, polymers (e.g. polyaniline, polypyrrole, PEDOT, poly(4-vinylpyridine)). While in a case of the mixed oxide semiconductor, we have explored formation the p-n heterojunction favoring increase of density of the electron population within the conduction band following deposition of TiO2 over the electrodeposited large crystals of Cu2O, in the latter case we tailor light absorption properties and affect the system’s stability. Upon illumination (from the copper(I) oxide side), charge transport to the reaction sites should be enhanced and the overall electric conductivity (at the catalytic interface) increases. Having in mind both hydrophilic and hydrophobic properties of Nafion over-coating, the outer-most ultra-thin film of Nafion, having properties of both robust (protective) layer and wetting (favoring proton mobility) medium, has been applied. Moreover, the outer-most over-layer of Nafion is expected to facilitate attraction of CO2 (dissolved in the sodium sulfate electrolyte) at the photoelectrochemically active mixed-metal-oxides interfaceSpecial attention has been paid to synthesis, characterization and optimization of the hybrid photocathode, namely the Nafion-protected mixed-oxides (Cu2O-TiO2) and polymer modified copper(I) oxide systems (deposited on fluorine-doped tin oxide covered glass, FTO) toward photoelectrochemical reduction of carbon dioxide.

There has been growing interest in the photoelectrochemical conversion of carbon dioxide (a potent greenhouse gas and a contributor to global climate change) to useful carbon-based fuels or chemicals. The reaction products are of potential importance to energy technology, food research, medical applications and fabrication of plastic materials. Given the fact that the CO2 molecule is very stable, its electroreduction processes are characterized by large overpotentials. It is often postulated that, during electroreduction, the rate limiting step is the protonation of the adsorbed CO product to form the CHO adsorbate. In this respect, the proton availability and its mobility at the photo(electro)chemical interface has to be addressed. On the other hand, competition between such parallel processes as hydrogen evolution and carbon dioxide reduction has also to be considered. Recently, we have concentrated on the development of hybrid materials by utilizing combination of metal oxide semiconductors thus capable of effective photoelectrochemical reduction of carbon dioxide. For example, the combination of titanium (IV) oxide and copper (I) oxide has been considered before and after sunlight illumination. Application of the hybrid system composed of both above-mentioned oxides resulted in high current densities originating from photoelectrochemical reduction of carbon dioxide mostly to methanol (CH3OH) as demonstrated upon identification of final products. Among important issue is intentional stabilization, activation, and functionalization of the mixed-metal-oxide-based photoelectrochemcal interface toward better long-term performance and selectivity production of small organic molecules (C1-C4) and other chemicals. In this respect, ultra-thin films of conducting polymers (simple or polyoxometallate-derivatized) and supramolecular complexes (with nitrogen containing ligands and certain transition metal sites), sub-monolayers of metals (Cu, Au), networks of noble metal (Au, Ag) nanoparticles or layers of robust bacterial biofilms have been considered. The photo-biocathode with Cu-containing enzyme has induced the reduction of not only oxygen but carbon dioxide as well, under illuminations with photon energies higher than silicon band gap. In the presentation, special attention will be paid to mechanistic aspects of electroreduction of carbon dioxide, fabrication and characterization of highly selective and durable semiconductor photoelectrode materials and to importance of the reaction conditions.

Investigations of the photo-induced phenomena enabling to improve and understand fundamental processes involved in CO2 reduction includes co-assembly of plasmonic and catalytic metal nanoparticles to the build-up of a semiconductor photocathode. Combination of the nanostructures of plasmonic metals, such as silver or gold with other metal electrocatalysts will substantially decrease the energy barriers of the CO2 reduction process through interaction of photo-excited surface plasmon states with adsorbed reaction intermediates. The significance to investigate reduction of CO2 at gold, silver and copper surfaces enhanced by the extra activation of the process provided by the illuminated, incorporated plasmonic metallic nanostructures is supported by the occurrence of the photo-emission process associated with the decay of photo-excited surface plasmons. Of particular interest will be a strong influence of the Ag/FTO electrode roughness upon the photo-emissive cathodic currents of electro-reduction of CO2 dissolved in aqueous solution. Actually, two metals Ag and Au, the nanostructures of which exhibit strong excitation of surface plasmon resonance through interaction with near UV and visible photons are also catalytically active toward electro-reduction of CO2. Besides the photo-emission, another property of plasmonic NPs – heat generation resulting from the absorption of incident photons and their influence on the reduction of CO2 at composite cathodes will be the objectives of this presentation.

There has been growing interest in the electrochemical reduction of carbon dioxide, a potent greenhouse gas and a contributor to global climate change. Given the fact that the CO2 molecule is very stable, its electroreduction processes are characterized by large overpotentials. To produce highly efficient and selective electrocatalysts, the transition-metal-based molecular materials are often considered. It is believed that, during electroreduction, the rate limiting step is the protonation of the adsorbed CO product to form the CHO adsorbate. To optimize the hydrogenation-type electrocatalytic approach, we have proposed to utilize nanostructured metallic centers (e.g. Pd, Pt or Ru) in a form of highly dispersed and reactive nanoparticles generated within supramolecular network of distinct nitrogen, sulfur or oxygen-coordination complexes. Reduction of carbon dioxide begins now at less negative potentials and is accompanied by significant enhancement of the reduction current densities. Among important issues are the mutual completion between hydrogen evolution and carbon dioxide reduction and specific interactions between coordinating centers and metallic sites. We have also explored the ability of biofilms to form hydro-gel-type aggregates of microorganisms attached to various surfaces including those of carbon electrode materials. Biofilms are able to transfer electrons to and from electrodes, and they can act in a manner analogous to redox or conducting polymer films on electrodes. Here we have explored a biofilm formed by a strain of Yersinia enterocolitica as active bioelectrocatalytic support; it is characterized by long-term stability over wide ranges of pH (4-10) and temperatures (0-40°C). Upon incorporation of various noble metal nanostructures and/or conducting polymer ultra-thin films, a highly reactive and selective system toward CO2-reduction is obtained. Another possibility to enhance electroreduction of carbon dioxide is to explore direct transformation of solar energy to chemical energy using transition metal oxide semiconductor materials. We show here that, by intentional and controlled combination of metal oxide semiconductors, we have been able to drive effectively photoelectrochemical reduction of carbon dioxide. The combination of titanium (IV) oxide and copper (I) oxide has been explored toward the reduction of CO2 before and after illumination. Application of the hybrid system composed of both oxides has resulted in high current densities originating from photoelectrochemical reduction of carbon dioxide mostly to methanol, as demonstrated upon identification of final products using conventional and mass-spectrometry-assisted gas chromatography. A role of TiO2 is not only stabilizing: the oxide is also expected to prevent the recombination of charge carriers. Bacterial-biofilm-enhanced photoelectrochemical interfaces for improved reduction of carbon dioxide will also be considered.

Investigations of the photo-induced phenomena enabling to improve and understand fundamental processes involved in CO2 reduction includes co-assembly of plasmonic and catalytic metal nanoparticles to the build-up of a semiconductor photocathode. Combination of the nanostructures of plasmonic metals, such as silver or gold with other metal electrocatalysts will substantially decrease the energy barriers of the CO2 reduction process through interaction of photo-excited surface plasmon states with adsorbed reaction intermediates. The significance to investigate reduction of CO2 at gold, silver and copper surfaces enhanced by the extra activation of the process provided by the illuminated, incorporated plasmonic metallic nanostructures is supported by the occurrence of the photo-emission process associated with the decay of photo-excited surface plasmons. Of particular interest will be a strong influence of the Ag/FTO electrode roughness upon the photo-emissive cathodic currents of electro-reduction of CO2 dissolved in aqueous solution. Actually, the two metals Ag and Au, the nanostructures of which exhibit strong excitation of surface plasmon resonance through interaction with near UV and visible photons are also catalytically active toward electro-reduction of CO2. Besides the photo-emission, another property of plasmonic NPs – heat generation resulting from the absorption of incident photons and their influence on the reduction of CO2 at composite cathodes will be the objectives of this presentation.

Attempts to improve performance of the semiconductor photo-electrodes used either for oxidation or reduction of species present in the electrolyte very often require presence of a catalysts However, identification of new molecular catalysts, active in often highly corrosive media or under unfavourable band energetics is a challenge. N-type mesoporous tungsten trioxide, WO3, is one of few stable semiconductor materials able to photo-electrochemically split water under solar light irradiation but it’s operational acidic environment restricts use of any catalyst to the precious metal based oxygen-evolution electrocatalysts. In an attempt to overcome this limitation, an addition to the acidic electrolyte of Keggin-type polyoxometalates (POMs) species was investigated in function of their electrocatalytic capabilities to drive oxygen evolution. The presence of this catalyst in the electrolyte makes it particularly efficient for use with nanoporous structure allowing deep penetration of the catalyst dissolved in the electrolyte. Moreover, moderate doping with metal cations of WO3 has been found to enhance visible blue light absorption of tungsten trioxide and, consequently, its photocurrent conversion efficiency. Combination of those two effects allowed achieving of record high water photooxidation currents attained under simulated solar AM 1.5G irradiation. The enhancement of anodic photocurrents will be discussed in the frame of functionalization of different mixed metal oxides with the POMs and correlated with the measurements of the amounts of oxygen evolved at the modified electrodes.

Numerous homogeneous and heterogeneous catalytic systems have been proposed to induce the CO2 reduction and, depending on reaction conditions (applied potential, strength of the electrolyte, local pH, local concentration of CO2 and the catalyst applied), various products can be obtained. Because the CO2 molecule is very stable, its electroreduction would be characterized by large over-potentials. In this respect, behavior of carbon dioxide resembles that of dioxygen. In both cases, the limiting steps involve protonation of the respective species. A crucial problem in designing effective electrocatalytic systems for the reduction of carbon dioxide is the necessity to cope with the another competitive process, namely the simultaneous hydrogen evolution. Mechanisms of reductions of both carbon dioxide and protons are dependent not only on the proton availability and mobility at the electrocatalytic interface but also on the presence the adsorbed hydrogens at the active catalytic sites. In this respect, numerous metallic catalysts (e.g. Cu, Pd, Pt) have been proposed. Alternate approaches to efficient electroreduction of carbon dioxide my refer to utilization of biological systems. Recently, whole cell biocatalysts and microbial electrocatalysts have been considered. Microorganisms can form very stable biofilms well-adhering to different solid surfaces. We propose here a hybrid (biofilm-based organic-inorganic) support or matrix for catalytic (noble metal) nanoparticles. The system was obtained by consecutive deposition of the porous polyaniline-supported bacterial biofilm (Yersinia enterocolitica) and multi-walled carbon nanotubes. Although this biofilm does not exhibit appreciable activity toward reduction of carbon dioxide, its structure (while being robust) contains open water channels existing between the bacterial micro-colonies thus permitting unimpeded flow of the aqueous electrolyte. The system’s performance will also be discussed with respect to the oxygen reduction. To appreciate effective reduction of carbon dioxide, instead of conventional Pd nanoparticles, nanosized Pd immobilized within supramolecular assemblies of tridentate Schiff-base ligands or supported onto hybrid biofilm-based matrices have been considered. Reduction of carbon dioxide begins now at less negative potentials and is accompanied by significant enhancement of the CO2-reduction current densities. Among important issues are specific interactions between nitrogen coordinating centers and metallic palladium sites. interface. The above activating phenomena will also be verified during oxygen reduction. Through intentional and controlled combination of metal oxide semiconductors, we have been able to drive effectively photo-electrochemical reduction of carbon dioxide. The combination of titanium (IV) oxide (TiO2) and copper (I) oxide (Cu2O) has been explored toward the reduction of carbon (IV) oxide (CO2) before and after sunlight illumination. Application of the hybrid system composed of both above-mentioned oxides resulted in high current densities originating from photoelectrochemical reduction of carbon dioxide mostly to methanol (CH3OH) as demonstrated upon identification of final products. The role of TiO2 is not only in stabilizing the interface: the oxide is also expected to prevent the recombination of charge carriers. Possibility of further decoration with traces of the conventional noble-metal-based systems (mentioned above) will be also addressed.

Titanates are known from their photocatalytic properties, but they need additional catalysts to work efficiently also they have very high electronic conductivity when they are prepared under reducing conditions in the hydrogen flame or under thermal oxidation in high temperature. We prepared these non-stechiometric titanates as materials for visible-light water and/or small organic molecules oxidation. Specific conditions of synthesis of non-stechiometric titanates, created by oxidation of the metal at high temperature in oxygen flow, allowed to get unique properties of such films like: large surface area, high conductivity, red-shift in the absorption spectrum and stability over large range of pHs. Adding to these properties, the affinity of polyoxometalate (POMs) species to the formed structures, and their ability to catalyse the water oxydation reaction, the system of TiO2-x – POM seems to be suitable for water splitting purposes under visible light irradiation. Morover, these sub-stoechiometric titanium dioxide / titanes films exhibited red-shifted IPCE photo-action spectrum. These results demonstrated the possibility to form defective TiO2 through thermal oxidation of the titanium metal as alternative to the reduction by H2.

There has been growing interest in the electrochemical reduction of carbon dioxide (CO2), a potent greenhouse gas and a contributor to global climate change, and its conversion into useful carbon-based fuels or chemicals. Numerous homogeneous and heterogeneous catalytic systems have been proposed to induce the CO2 reduction and, depending on the reaction conditions various products that include carbon monoxide, oxalate, formate, carboxylic acids, formaldehyde, acetone or methanol, in addition to various hydrocarbons at different ratios. Given the fact that the CO2 molecule is very stable, its electroreduction processes are characterized by large overpotentials. To produce highly efficient and selective electrocatalysts, the transition-metal-based molecular materials are often considered. It is believed that, during electroreduction, the rate limiting step is the protonation of the adsorbed CO product to form the CHO adsorbate. Because reduction of CO2 can effectively occur by hydrogenation, to optimize the conventional electrocatalytic approach, we propose such a model catalytic system as nanostructured metallic palladium capable of absorbing reactive hydrogen in addition to the ability to adsorb monoatomic hydrogen at the interface. Under such conditions, the two-electron reduction of CO2 typically to CO is favored. To produce highly dispersed and reactive nanoparticles, we generate them by electrodeposition from N-coordination complexes of palladium(II). The resulting metallic Pd nanoparticles, rather than Pd cationic species, are stabilized and activated by nitrogen coordination centers from the macromolecular matrix. In the present research, we demonstrate that stabilization and activation of highly dispersed nanostructured metallic Pd centers with a supramolecular architecture of “privileged ligands” results in the electrocatalytic enhancement of the CO2 reduction. Reduction of carbon dioxide begins now at less negative potentials and is accompanied by significant enhancement of the CO2-reduction current densities. Among important issues are specific interactions between nitrogen coordinating centers and metallic palladium sites at the electrocatalytic interface. Another possibility to enhance electroreduction of carbon dioxide is to explore direct transformation of solar energy to chemical energy using transition metal oxide semiconductor materials. We show here that, by intentional and controlled combination of metal oxide semiconductors, we have been able to drive effectively photoelectrochemical reduction of carbon dioxide. The combination of titanium (IV) oxide (TiO2) and copper (I) oxide (Cu2O) has been explored toward the reduction of carbon (IV) oxide (CO2) before and after sunlight illumination. Application of the hybrid system composed of both above-mentioned oxides resulted in high current densities originating from photoelectrochemical reduction of carbon dioxide mostly to methanol (CH3OH), as demonstrated upon identification of final products using conventional and mass-spectrometry assisted gas chromatography. On mechanistic grounds, the role of TiO2 seems to be not only stabilizing: the oxide is also expected to prevent the recombination of charge carriers.

An effective solar light-driven water splitting in photo-electrochemical devices requires use of materials which combine high photo-conversion efficiency and long term stability. For the latter reason the choice of the suitable systems is restricted to the semiconducting oxides that, in most cases, do not undergo photo-corrosion in aqueous solutions and are able to absorb efficiently the visible light. However, although the nanostructured scaffold of the semiconducting photo-electrodes contributes generally to decrease the bulk charge recombination by reducing the minority charge carriers pathway to reach the solution species, at the same time, it tends to enhance the recombination of charges at the surface due to the increased contact area with the electrolyte. Common approach to reduce recombination losses, involves deposition at the photo-electrode surface of electrocatalysts allowing to overcome slow kinetics of oxygen evolution. There are only few, precious metal (Pt, IrO2), oxygen-evolution electrocatalysts that can be used in pH acidc in which WO3 operates effectively. In this regard, we will present an increase of water photo-oxidation currents at WO3 photo-anodes, caused by presence of polyoxometalates (POMs), such as phosphomolybdate (PMoO40 3-) Keggin type ions. This class of compounds is known to undergo reversible, stepwise multi-electron transfer reactions that are combined with their excellent proton conductivity. What is more, the POMs might act as a buffer layer when form a cover for a metallic nano - particles largely used as a regular catalysts. The POMs may act either as relays for photogenerated electrons or as catalysts directly involved in the hole transfer reactions. In particular, they may affect the pathway of water oxidation by modifying the stability of the intermediates (e.g., peroxides) involved in this processes. Ongoing efforts devoted to minimize the bias voltage required to perform visible light-driven photo-oxidation of water at NS WO3 photoanodes also include the use of dopants or incorporation of plasmonic metal nanostructures allowing to enhance the light capture by the WO3 films1. 1. R. Solarska, K. Bienkowski, S. Zoladek, A. Majcher, T. Stefaniuk, P. J. Kulesza and J. Augustynski, Angew. Chem. Int. Ed. 2014, 53: DOI: 10.1002/anie.201408374

Due to gradual decline of energy resources, there has been growing interest in new energy systems that include direct transformation of solar energy to chemical energy using oxide semiconductor materials. Furthermore, carbon dioxide (CO2), as the primary greenhouse gas also emitted through human activities, could be converted using sunlight to organic compounds. The approach permits simultaneous generation of alternative fuels and environmental remediation of carbon emissions from the continued use of conventional fuels. The aim of this work has been to develop hybrid materials by utilizing combination of metal oxide semiconductors thus capable of effective photoelectrochemical reduction of carbon dioxide. The combination of titanium (IV) oxide (TiO2) and copper (I) oxide (Cu2O) has been explored toward the reduction of carbon (IV) oxide (CO2) before and after sunlight illumination. Application of the hybrid system composed of both above-mentioned oxides resulted in high current densities originating from photoelectrochemical reduction of carbon dioxide mostly to methanol (CH3OH) as demonstrated upon identification of final products. In particular, fabrication of the hybrid system (heterojunction photocathode) of TiO2 and Cu2O (on the conducting glass) has required first the cathodic electrodeposition copper (I) oxide. The latter step has been followed by sputtering n-type titanium (IV) oxide. The spectral responses of the Cu2O/TiO2­ electrode is comparable to that of simple Cu2O, and the photoresponse is enhanced at relatively short wavelengths. It is reasonable to expect that the light absorbed by the inner Cu2O film produces energetic electron (e-) – hole (h+) pairs. The excited electrons are driven through the conduction band to the external TiO2/electrolyte interface. The role of TiO2 is not stabilizing; the oxide is also expected to prevent the recombination of charge carriers (e- - h+ pairs). By using gas chromatography with the flame ionization detector, it was confirmed that methanol predominates as a final product.

We investigated the structure and photo-electrochemical properties for water splitting of tungsten trioxide-ferric oxide thin films formed by spray pyrolysis. While annealing at 600°C produces films consisting of a mixture of monoclinic WO 3 and hematite α- Fe 2 O 3, the heating at a temperature above 1000°C affords formation of ferric tungstate Fe 2 WO 6. Both kinds of films exhibit optical absorption range comparable or exceeding that of α- Fe 2 O 3. Another important feature is a decreased rate of charge recombination of the mixed-oxide Fe 2 O 3- WO 3 with respect to the ferric oxide photo-anodes.

There has been growing interest in the electrochemical reduction of carbon dioxide (CO2), a potent greenhouse gas and a contributor to global climate change, and its conversion into useful carbon-based fuels or chemicals. Numerous homogeneous and heterogeneous catalytic systems have been proposed to induce the CO2 reduction and, depending on the reaction conditions (applied potential, choice of buffer, its strength and pH, local CO2 concentration or the catalyst used), various products that include carbon monoxide, oxalate, formate, carboxylic acids, formaldehyde, acetone or methanol, as well as such hydrocarbons as methane, ethane, and ethylene, are typically observed at different ratios. These reaction products are of potential importance to energy technology, food research, medical applications and fabrication of plastic materials. Given the fact that the CO2 molecule is very stable, its electroreduction processes are characterized by large overpotentials, and they are not energy efficient. To produce highly efficient and selective electrocatalysts, the transition-metal-based molecular materials are often considered. Because reduction of CO2 can effectively occur by hydrogenation, in the present work, we concentrate on such a model catalytic system as nanostructured metallic palladium capable of absorbing reactive hydrogen in addition to the ability to adsorb monoatomic hydrogen at the interface. We are going to demonstrate that palladium nanocenters can be generated within the coordination architecture of tridentate Schiff-base-ligands by electrodeposition from the supramolecular complex of palladium(II), [Pd(C14H12N2O3)Cl2]2∙MeOH. The resulting Pd nanoparticles (diameters, 5-10 nm) are stabilized and activated by nitrogen coordination sites, and the electrocatalytic system exhibits appreciable activity toward reduction carbon oxide (IV) in 0.1 mol dm-3 KHCO3. The respective voltammetric peak currents are ca. three times larger than those observed at conventional palladium nanoparticles (diameter, ca. 10-20 nm) under analogous experimental conditions and at the same loading of palladium (100 μg cm-2). Despite that fact that the degree of agglomeration of nanostructured palladium is much lower when it has been generated within the macromolecular network, it is reasonable to expect that some specific interactions between nitrogen coordination centers and metallic Pd exist. The process of electrosorption of hydrogen at the Schiff-base-ligand supported palladium nanostructures seems to be more reversible (when investigated in KHCO3) and dominated by the hydrogen absorption rather than the surface adsorption phenomena (characteristic of conventional Pd nanoparticles). We are also going to address the possibility of combining copper oxide nanostructures together with coordinatively supported Pd nanocenters to drive photoelectrocatalytic reduction of carbon dioxide. Acknowledgement We appreciate collaboration with Adam Gorczynski, Maciej Kubicki, and Violetta Patroniak from Faculty of Chemistry, Adam Mickiewicz University, Poznan, Poland that has led to fabrication of functionalized palladium supramolecular coordination compound.

An effective solar light-driven water splitting in photo-electrochemical devices requires use of materials which combine both high photo-conversion efficiency and long term stability goals. For the latter reason the choice of the suitable systems is restricted to the semiconducting oxides that, in most cases, do not undergo photo-corrosion in aqueous solutions but which are also able to absorb efficiently the visible light. The low optical absorption coefficients near the fundamental band edge, which determine the extent of solar light absorption by many photo-anode materials, are the critical factors for a number of semiconductors characterized by an indirect optical transition. This is also the case of n-type semiconducting WO3 or Fe2O3 responding to the blue, respectively, green part of the solar spectrum for which the optical absorption depths exceed the minority charge carriers collection distances.Therefore, incoupling of light into semiconductor films by scattering from plasmonic nanostructures and/or resonant coupling of the plasmonic near field to the semiconductor, have a potential to improve the effectiveness of the photocurrent spectral response of the employed photoanode. The results regarding the improved light absorption and charge collection in doped and/or mixed semiconducting oxide photo-anodes will be presented.