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 ...

Coupling the photo-oxidation of biomass derived substrates with water splitting in a photoelectrochemical (PEC) cell is a broadly discussed approach intended to enhance efficiency of hydrogen generation at the cathode. Here, we report a PEC device employing a nanostructured semitransparent WO3 photoanode that, irradiated with simulated solar light achieves large photocurrents of 6.5 mA cm−2 through oxidation of glucose, a common carbohydrate available in nature that can be obtained by processing waste biomass. The attained photocurrents are in a large part due to the occurrence of the photocurrent doubling, where oxidation of glucose by the photogenerated positive hole is followed by injection by the formed intermediate of an electron into the conduction band of WO3. Selection of an appropriate supporting electrolyte enabled effective reforming of glucose into valuable products: gluconic and glucaric acids, erythrose and arabinose with up to 64% total Faradaic yield attained at ca 15% glucose conversion.

No abstract

Electron transfer (ET) reactions in bioelectrocatalysis of enzymes at electrode surfaces require not only the efficient immobilization, but also highly conductive nanostructured platform, which allows for retaining its bioactivity and structural conformation. The novel architecture of spatially separated electrochemically reduced graphene oxide (ERGO) by multi‐walled carbon nanotubes functionalized with 4‐(pyrrole‐1‐yl) benzoic acid (MWCNT/PyBA) with the accurate porous structure could be an alternative for earlier approaches to the construction of bioelectrocatalytic systems with rapid diffusion of reagents from the solution to the enzyme molecule. The formation of ERGO/MWCNT/PyBA system was confirmed by electrochemical, spectroscopic and microscopic methods. The cyclic voltammetry experiments revealed that the presence of ERGO in the conductive material affects the electronic communication between the enzyme molecule and modified electrode surface greatly improving its ET properties resulting in a double increase of the heterogeneous ET rate constant value (ks=6.5 s−1). The fabricated glucose oxidase based biosensor sensitively detects glucose, therefore, ERGO/MWCNT/PyBA architecture could provide a novel and efficient platform for immobilization of redox enzymes.

N-type semiconducting WO 3 is widely investigated as a photoanode operating in water and seawater splitting devices. Because of the propensity of WO 3 to favor photo-oxidation of acidic electrolyte anions and, in parallel, the formation on the electrode surface of the peroxo species, the choice of the appropriate electrolyte to allow stable operation of the photoanode is of critical importance. Our results from structural and photoelectrochemical tests performed using mesoporous WO 3 photoanodes exposed to 80 h long photoelectrolysis in a 1 M aq. methanesulfonic acid supporting electrolyte demonstrate the photostability of both the WO 3 photomaterial and the CH 3 SO 3 H electrolyte. The reasons for the stability of aqueous solutions of CH 3 SO 3 H are discussed on the basis of earlier literature reports.