Demonstration of Scalable Water Splitting into H and O by a Flow-Type Photocatalysis-Electrolysis Hybrid System Using a Highly Stable Photocatalyst.

Water splitting via a photocatalysis-electrolysis hybrid system has been investigated as a potentially scalable and economically feasible means of producing renewable H. However, there are no reports demonstrating a scalable system for stoichiometric water splitting using an efficient and stable photocatalyst, and the key operating conditions for efficiently driving the entire system have not been established. Herein, we address the issues required to efficiently drive the entire system of a Cs, Fe, and H ion-modified WO (denoted as H-Fe-Cs-WO) photocatalyst fixed reactor combined with a polymer electrolyte membrane (PEM)-type electrolyzer.

Simultaneous production of hydrogen and chlorine through overall brine splitting with a particulate photocatalyst.

Sunlight-driven photocatalytic water splitting shows promise for green H production. In an attempt to achieve seawater splitting, we constructed a new stoichiometric brine splitting system that produces H along with Cl instead of O. Cl-a more potent high-value-added oxidant than O-was obtained with 100% selectivity over 10 h by adjusting the solution pH to acidic using a UV-light-driven Pt-loaded TiO photocatalyst.

Surface-modified, dye-sensitized niobate nanosheets enabling an efficient solar-driven Z-scheme for overall water splitting.

While dye-sensitized metal oxides are good candidates as H evolution photocatalysts for solar-driven Z-scheme water splitting, their solar-to-hydrogen (STH) energy conversion efficiencies remain low because of uncontrolled charge recombination reactions. Here, we show that modification of Ru dye-sensitized, Pt-intercalated HCaNbO nanosheets (/Pt/HCaNbO) with both amorphous AlO and poly(styrenesulfonate) (PSS) improves the STH efficiency of Z-scheme overall water splitting by a factor of ~100, when the nanosheets are used in combination with a WO-based O evolution photocatalyst and an I/I redox mediator, relative to an analogous system that uses unmodified /Pt/HCaNbO. By using the optimized photocatalyst, PSS//AlO/Pt/HCaNbO, a maximum STH of 0.

HO production on a carbon cathode loaded with a nickel carbonate catalyst and on an oxide photoanode without an external bias.

Efficient HO production both on a carbon cathode modified with various metal salts and on an oxide photoanode was investigated. The cathodic current density and faradaic efficiency for HO production (FE(HO)) on a carbon cathode in KHCO aqueous solution were significantly improved by the loading of an insoluble nickel carbonate basic hydrate catalyst. This electrode was prepared by a precipitation method of nickel nitrate and KHCO aqueous solution at ambient temperature.

Insights into the carbonate effect on water oxidation over metal oxide photocatalysts/photoanodes.

Photocatalytic/photoelectrochemical water splitting using metal oxide semiconductors is a promising technology for direct and simple solar-energy conversion. The addition of carbonate salts to an aqueous reaction solution has been known to promote stoichiometric O evolution and HO production HO oxidation. To elucidate the effect of carbonates, density functional theory calculations are performed to study the photoinduced HO and HCO oxidation mechanisms on TiO and BiVO.

Solar-to-Pharmaceutical Raw Material Production: Photoelectrochemical Naphthoquinone Formation Using Stabilized BiVO Photoanodes in Acid Media.

In the quest for efficient use of solar energy to produce high-value-added chemicals, we first achieved the photoelectrochemical (PEC) diketonization of naphthalene, using a BiVO/WO photoanode, to obtain naphthoquinone, an important pharmaceutical raw material with excellent efficiency by solar energy conversion. In the electrochemical (EC) reaction using F-doped SnO (FTO) substrates and a 0.5 M HSO HO-acetone (60 vol %) mixed solution containing 5 mM naphthalene, we produced a small amount of naphthoquinone evolution in the dark.

Acid-Resistant BiVO Photoanodes: Insolubility Control by Solvents and Weak W Diffusion in the Lattice.

We have revealed for the first time that BiVO photoanodes can be used even in strong acid media by mixing organic solvents into the electrolyte and depositing multilayers with a WO bottom layer. In general, the BiVO photoanodes are photocorrosive, especially in acid solutions. However, this shortcoming has been overcome using a combination of the two aforementioned modifications.

Functions of MnO in NaCl Aqueous Solution for Artificial Photosynthesis.

Photoelectrochemical water splitting has been intensively investigated as artificial photosynthesis technology to convert solar energy into chemical energy. The use of seawater and salted water has advantages for minimum environmental burden; however, the oxidation of Cl ion to hypochlorous acid (HClO), which has toxicity and heavy corrosiveness, should occur at the anode, along with the oxygen evolution. Here, O and HClO production in aqueous solution containing Cl on photoanodes modified with various metal oxides was investigated.

Electrochemical and Photoelectrochemical Water Oxidation for Hydrogen Peroxide Production.

Hydrogen peroxide (H O ), as a green fuel and oxidant, has drawn increasing attention in the energy and environmental research. Compared with the traditional anthraquinone process, the electrochemical (EC) and photoelectrochemical (PEC) syntheses of H O are cost-effective and environmentally friendly. In order to construct membraneless EC/PEC devices for the full H O synthesis, anodic H O production by water oxidation, which is less developed than cathodic H O generation, is highly desirable.

An Artificial Z-Scheme Constructed from Dye-Sensitized Metal Oxide Nanosheets for Visible Light-Driven Overall Water Splitting.

Sensitization of a wide-gap oxide semiconductor with a visible-light-absorbing dye has been studied for decades as a means of producing H from water. However, efficient overall water splitting using a dye-sensitized oxide photocatalyst has remained an unmet challenge. Here we demonstrate visible-light-driven overall water splitting into H and O using HCaNbO nanosheets sensitized by a Ru(II) tris-diimine type photosensitizer, in combination with a WO-based water oxidation photocatalyst and a triiodide/iodide redox couple.

PINO/NHPI-mediated selective oxidation of cycloalkenes to cycloalkenones via a photo-electrochemical method.

The selective photo-electrochemical oxidation of cyclohexene to 2-cyclohexene-1-one was successfully performed with excellent Faraday efficiency (>99%) via indirect oxidation with a PINO/NHPI mediator and O on a BiVO/WO photoanode under low applied bias.

Photo-Electrochemical C-H Bond Activation of Cyclohexane Using a WO Photoanode and Visible Light.

The photo-electrochemical C-H bond activation of cyclohexane to produce cyclohexanol and cyclohexanone (KA oil) with high partial oxidation selectivity (99 %) and high current utilization ratio (76 %) was achieved in air at room temperature at atmospheric pressure. The production rate of KA oil was accelerated by applying a bias. The incident photon to current efficiencies at 365 and 420 nm were 57 % and 24 %, respectively.

Photoelectrochemical Hydrogen Peroxide Production from Water on a WO /BiVO Photoanode and from O on an Au Cathode Without External Bias.

The photoelectrochemical production and degradation properties of hydrogen peroxide (H O ) were investigated on a WO /BiVO photoanode in an aqueous electrolyte of hydrogen carbonate (HCO ). High concentrations of HCO species rather than CO species inhibited the oxidative degradation of H O on the WO /BiVO photoanode, resulting in effective oxidative H O generation and accumulation from water (H O). Moreover, the Au cathode facilitated two-electron reduction of oxygen (O ), resulting in reductive H O production with high current efficiency.

Efficient oxidative hydrogen peroxide production and accumulation in photoelectrochemical water splitting using a tungsten trioxide/bismuth vanadate photoanode.

An aqueous solution of hydrogen carbonate (HCO3(-)) facilitated oxidative hydrogen peroxide (H2O2) production from water on a WO3/BiVO4 photoanode with the simultaneous production of hydrogen (H2) on a Pt cathode even at an applied voltage far lower than the theoretical electrolysis voltage (+1.77 V vs. RHE) under simulated solar light.

Discovery of Overcoating Metal Oxides on Photoelectrode for Water Splitting by Automated Screening.

We applied an automated semiconductor synthesis and screen system to discover overcoating film materials and optimize coating conditions on the BiVO4/WO3 composite photoelectrode to enhance stability and photocurrent. Thirteen metallic elements for overcoating oxides were examined with various coating amounts. The stability of the BiVO4/WO3 photoelectrode in a highly concentrated carbonate electrolyte aqueous solution was significantly improved by overcoating with Ta2O5 film, which was amorphous and porous when calcined at 550 °C.

A comparative computational study on the interactions of N719 and N749 dyes with iodine in dye-sensitized solar cells.

The intermolecular interactions of the two most basic Ru(II) complex dyes for dye-sensitized solar cells (DSSCs), N719 and N749, with the iodine species are investigated using density functional theory (DFT). In addition to interactions with a single I2 molecule, multiple I2 interactions and simultaneous interactions of I2 and I(-) occur. N719 with two isothiocyanato (NCS) ligands interacts with two I2 molecules via the two terminal S atoms in the ground singlet electronic state, whereas N749 with three NCS ligands forms three S···I-I bonds.

Intermolecular interactions between a Ru complex and organic dyes in cosensitized solar cells: a computational study.

Intermolecular interactions in cyclometalated Ru complex dye (FT89) dimers, carbazole organic dye (MK-45 and MK-111) dimers, FT89-MK-45 complexes, and FT89-MK-111 complexes were investigated using density functional theory (DFT) and time-dependent DFT (TD-DFT) to elucidate the improvement mechanism of dye-sensitized solar cell (DSSC) performance due to cosensitization with FT89 and MK dyes. All of the dimers and complexes form intermolecular cyclic hydrogen bonds via the carboxyl groups. The FT89 dimer and complexes with the TiO2Na model system promote intermolecular interactions with I2via the NCS ligand of the FT89 monomer.

Combinatorial search for iron/titanium-based ternary oxides with a visible-light response.

A combinatorial approach has been carried out to systematically investigate visible-light responsiveness of Fe-Ti-M (M: various metal elements) oxides for photoelectrochemical water splitting. Among the 25 elements tested, strontium was the most effective. A ternary metal oxide with the composition Fe(86.

Complete oxidation of acetaldehyde and toluene over a Pd/WO(3) photocatalyst under fluorescent- or visible-light irradiation.

Acetaldehyde was completely oxidized to CO(2) over a Pd/WO(3) photocatalyst under fluorescent-light irradiation in a flow-type reactor, and Pd/WO(3) was also used to completely oxidize toluene to CO(2) in a batch reactor under visible-light irradiation.