semiconductor photocatalytic particles, pure water is generally used and both reduction and oxidation reaction products, H 2 and O 2 , are formed in the same cell compartment and should be subsequently separated. [2,3] On the other hand, employing a photoelectrolysis cell with separated anodic and cathodic compartments imposes use of a supporting electrolyte with ionic conductivity large enough to avoid excessive Ohmic losses within the cell. [4,6] The choice of the appropriate electrolyte is even more important when relatively thick nanoporous film photoelectrodes with high internal photoactive surface area are employed, where too low conductivity of the electrolyte may adversely affect the amount of collected photocurrent due to uneven current distribution across the semiconductor film. [7] Consequently, in addition to pure water, also the chemicals required to prepare electrolyte for the photoelectrolysis cell will potentially constitute a nonnegligible part of the operational cost of larger scale photoelectrochemical (PEC) water splitting devices. The fact that cannot at all be neglected-extensive utilization for electrolysis of fresh water would put heavy pressure on vital water resources.Since the seawater is a free and widely abundant electrolyte, there were various attempts to use it in the PEC [8][9][10][11][12][13] and conventional electrochemical [14] devices to produce hydrogen. From the practical viewpoint, the photoelectrolysis of seawater requires at first identification of photoanode materials stable in the presence of chloride ions under highly oxidizing conditions. Only few among works reported on the PEC seawater splitting describe experiments conducted under visible light irradiation. An electrode consisting of molybdenum-doped bismuth vanadate (Mo-BiVO 4 ) reached, under simulated AM 1.5G (100 mW cm −2 ) illumination, a photocurrent of 2.2 mA cm −2 at 1 V versus RHE (reversible hydrogen electrode). [9] Loading the Mo-BiVO 4 electrode with precious metal RhO 2 catalyst was effective in limiting to ≈10% the drop of the photocurrent over a 5 h long stability test. Analysis of the photoelectrolysis A seawater splitting photoelectrochemical cell featuring a nanostructured tungsten trioxide photoanode that exhibits very high and stable photocurrents producing chlorine with average 70% Faradaic efficiency is described. Fabrication of the WO 3 electrodes on fluorine-doped tin oxide substrates involves a simple solution-based method and sequential layer-by-layer deposition with a progressively adjusted amount of structure-directing agent in the precursor and a two-step annealing. Such a procedure allows tailoring of thick, highly porous, structurally stable WO 3 films with a large internal photoactive surface area optimizing utilization of visible light wavelengths by the photoanode. With the application of an anodic potential of 0.76 V versus Ag/AgCl reference electrode (0.4 V below the thermodynamic Cl 2 /Cl − potential) in synthetic seawater, the designed WO 3 photoanodes irradiated with simulated ...

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 materials able to operate as stable and efficient photoanodes in a water photoelectrolysis cell. Here, we demonstrate that photocatalytic water oxidation currents on thin-layer semitransparent WO 3 electrodes, deposited by using a one-step sol−gel method on conductive oxide F-SnO 2 substrates, are dramatically improved following additional highertemperature (ca. 700 °C) annealing. Largely reduced recombination of charge carriers photogenerated in activated WO 3 associated with enhanced light absorption yields at 1.23 V vs RHE, under simulated solar AM 1.5G irradiation (100 mW cm −2 ), water photo-oxidation currents close to 4.2 mA cm −2 on a 1.2-μmthick photoanodeapproximately 2 times larger than on the electrodes of the same thickness only annealed at 550 °C. The relative enhancement of the photocurrent induced by the further annealing at 700 °C scaled up with decreasing the film thickness with a 3-fold increase observed for the thinnest tested, 0.25-μm-thick WO 3 electrode that reaches 2.75 mA cm −2 . We obtained such high photocatalytic water splitting performance without depositing any additional water oxidation catalyst.

Pairing cations with weakly coordinating anions (WCAs) often renders them highly Lewis-acidic and extremely reactive. Although these features are often desirable, excessive reactivity of a cation may lead to decomposition of solvents or WCAs, hindering isolation, storage and practical use of such species. In an attempt to mitigate the problem, we introduce a series of readily available novel Co(II)-WCA salts with the metal center stabilized by weakly bound ligands: SO 2 , halogenated acetonitriles and nitromethane with comprehensive characterization including structural, magnetic and spectral (IR) properties as well as thermal stability assessment. The use of these simple yet rarely encountered ligands yields mostly stable and highly Lewis-acidic com-plexes, in some cases comparable to SbF 5 according to calculated Fluoride Ion Affinities. Highly acidic character of the species is also reflected in observed reactivity. Since the most convenient route towards the Co(II) complexes leads through silver salts, the results are complemented with characterization of a series of novel Ag(I) complexes with abovementioned ligands. Experimental part is backed with DFT calculations which gives insight into the structure and energetics of presented Co(II) complexes and shows that Co(II) center is available for substrates like olefins. This makes them good candidates for catalysts in reactions requiring the presence of Lewis acids.

N-type semiconductor-tungsten trioxide (WO3) finds application in a large variety of fields including photocatalysis, gas sensors, smart windows or as a substrate for heterogeneous catalysts. This presentation will focus on recent improvements in optoelectronic and photoelectrochemical (PEC) properties of WO3 thin films achieved in our laboratory. The semitransparent WO3 films are formed on F-doped tin oxide (FTO) conductive glass substrates, using a sol-gel method, by depositing the precursor layer-by-layer and annealing sequentially in the flow of oxygen. Use of appropriate mixtures of tungstic acid and organic structure-directing agents that form the WO3 film precursor, combined with a two-step annealing, allows the formation of highly crystalline nanostructured (NS) electrodes with controlled, large porosity. This renders possible the permeation of the whole mesoporous film by the electrolyte. Annealing of the as-deposited samples in oxygen above 500°C ensures structural ordering with formation of monoclinic WO3. Since none among photostable (metallic oxide) semiconductors exhibits band-edge energy levels that match those of hydrogen and oxygen evolution reactions to allow unassisted water splitting, the present efforts focus on minimizing the bias voltage required to perform visible light-driven photooxidation of water. In fact, a bias voltage of the order of 1 V may be provided by several single-junction PV cells likely to operate in a tandem device with the PEC cell. Despite visible-light absorption range of the WO3 films restricted to 500 nm, under standard conditions, i.e. at 1.23 V vs RHE and under simulated AM 1.5G solar light (100 mW/cm2), stable anodic water splitting photocurrents exceeding 4.5 mA/cm2 are regularly attained.This presentation will principally focus on photoelectrolysis experiments employing synthetic seawater electrolyte, in a two compartment (separated by a sintered glass diaphragm) cell, that showed dominant (with 60-70% Faradaic efficiency) formation of chlorine at the WO3 photoanode with remarkably stable photocurrents reaching 4.7 mA/cm2. In fact, as demonstrated in an earlier work from our laboratory1, the WO3 photoelectrodes exhibit preferentially oxidation of anions (including Cl-) of the acidic aqueous electrolytes. However, in contrast with the Cl- ions, the photooxidation of oxy-anions of acidic electrolytes leads generally to the "passivation" of the WO3 electrodes due to the formation of the surface layers of peroxo species.1 The only identified exception is the methane-sulfonic acid that allows oxygen generation at the WO3 photoanode with large stable photocurrents.2 In the case of seawater photoelectrolysis, the operating potential point at which the photocurrent approaches saturation occurs at ca 0.4 V below E(Cl-/Cl2)=1.36 V vs SHE. Consistently, the incident photon conversion efficiencies (IPCEs) reach a maximum of 85% over 390-410 nm range of wavelengths.3 Good mechanical and chemical stability of the WO3 electrodes in the presence of chlorine evolved from seawat...

The mini‐review is focused on application of silver and its compounds in fluoroorganic synthesis, and it reflects immense progress in this field which took place during the last two decades, with additional examples of reactivity of historical importance. Reactions of C−H, C−F, N−H and O−H bond functionalization, as well as catalysis of cycloaddition reactions and intramolecular rearrangement, retro‐rearrangement, and functional group migrations, have been described. Whenever available in original works, the reaction mechanisms were discussed. Since silver may be catalytically active in each of its available oxidation states from (0), via (I) and (II) to (III) with their immensely diverse properties, the organofluorine part is preceded by a brief overview of chemistry of silver in general. Uniqueness of silver among Group 11 elements is highlighted.