Polyoxocationic antimony oxide cluster with acidic protons.

The success and continued expansion of research on metal-oxo clusters owe largely to their structural richness and wide range of functions. However, while most of them known to date are negatively charged polyoxometalates, there is only a handful of cationic ones, much less functional ones. Here, we show an all-inorganic hydroxyiodide [HSbO][HSbIO][SbI]·25HO (), forming a face-centered cubic structure with cationic SbO clusters and two types of anionic clusters in its interstitial spaces.

Supramolecular photocatalysts fixed on the inside of the polypyrrole layer in dye sensitized molecular photocathodes: application to photocatalytic CO reduction coupled with water oxidation.

The development of systems for photocatalytic CO reduction with water as a reductant and solar light as an energy source is one of the most important milestones on the way to artificial photosynthesis. Although such reduction can be performed using dye-sensitized molecular photocathodes comprising metal complexes as redox photosensitizers and catalyst units fixed on a p-type semiconductor electrode, the performance of the corresponding photoelectrochemical cells remains low, , their highest incident photon-to-current conversion efficiency (IPCE) equals 1.2%.

Conduction Band Control of Oxyhalides with a Triple-Fluorite Layer for Visible Light Photocatalysis.

The discovery of building blocks offers new opportunities to develop and control properties of extended solids. Compounds with fluorite-type BiO blocks host various properties including lead-free ferroelectrics and photocatalysts. In this study, we show that triple-layered BiMO blocks (M = Bi, La, Y) in BiMOCl allow, unlike double-layered BiO blocks, to extensively control the conduction band.

Fe/Ru Oxide as a Versatile and Effective Cocatalyst for Boosting Z-Scheme Water-Splitting: Suppressing Undesirable Backward Electron Transfer.

The atificial Z-scheme is a promising and rational strategy for solar-to-chemical energy conversion such as water-splitting. In the Z-scheme, backward redox processes are an essential drawback that should be overcome to increase its efficiency. Here, we demonstrate that the simple co-loading of Fe/Ru oxide, (Fe,Ru)O, onto various photocatalysts effectively improves the efficiency of water oxidation by suppressing the undesirable backward oxidation of the redox reagent Fe.

Earth-Abundant Molecular Z-Scheme Photoelectrochemical Cell for Overall Water-Splitting.

A push-pull organic dye and a cobaloxime catalyst were successfully cografted on NiO and CuGaO to form efficient molecular photocathodes for H production with >80% Faradaic efficiency. CuGaO is emerging as a more effective p-type semiconductor in photoelectrochemical cells and yields a photocathode with 4-fold higher photocurrent densities and 400 mV more positive onset photocurrent potential compared to the one based on NiO. Such an optimized CuGaO photocathode was combined with a TaON|CoO photoanode in a photoelectrochemical cell.

Flux Synthesis of Layered Oxyhalide BiNbOCl Photocatalyst for Efficient Z-Scheme Water Splitting Under Visible Light.

An oxyhalide photocatalyst BiNbOCl has recently been proven to stably oxidize water under visible light, enabling the Z-scheme water splitting when coupled with another photocatalyst for water reduction. We herein report the synthesis of BiNbOCl particles via a flux method, testing various molten salts to improve its crystallinity and hence photocatalytic activity. The eutectic mixture of CsCl/NaCl with a low melting point allowed the formation of single-phase BiNbOCl at as low as 650 °C.

Mimicking Natural Photosynthesis: Solar to Renewable H Fuel Synthesis by Z-Scheme Water Splitting Systems.

Visible light-driven water splitting using cheap and robust photocatalysts is one of the most exciting ways to produce clean and renewable energy for future generations. Cutting edge research within the field focuses on so-called "Z-scheme" systems, which are inspired by the photosystem II-photosystem I (PSII/PSI) coupling from natural photosynthesis. A Z-scheme system comprises two photocatalysts and generates two sets of charge carriers, splitting water into its constituent parts, hydrogen and oxygen, at separate locations.

New rare earth hafnium oxynitride perovskites with photocatalytic activity in water oxidation and reduction.

RHfON perovskites with R = La, Nd and Sm show a GdFeO-type structure and are semiconductors with band gaps of 3.35, 3.40 and 2.

Valence Band Engineering of Layered Bismuth Oxyhalides toward Stable Visible-Light Water Splitting: Madelung Site Potential Analysis.

A layered oxychloride BiNbOCl is a visible-light responsive catalyst for water splitting, with its remarkable stability ascribed to the highly dispersive O-2p orbitals in the valence band, the origin of which, however, remains unclear. Here, we systematically investigate four series of layered bismuth oxyhalides, BiOX (X = Cl, Br, I), BiNbOX (X = Cl, Br), BiGdOX (X = Cl, Br), and SrBiOX (X = Cl, Br, I), and found that Madelung site potentials of anions capture essential features of the valence band structures of these materials. The oxide anion in fluorite-like blocks (e.

Hybrid photocathode consisting of a CuGaO p-type semiconductor and a Ru(ii)-Re(i) supramolecular photocatalyst: non-biased visible-light-driven CO reduction with water oxidation.

A CuGaO p-type semiconductor electrode was successfully employed for constructing a new hybrid photocathode with a Ru(ii)-Re(i) supramolecular photocatalyst (/CuGaO). The /CuGaO photocathode displayed photoelectrochemical activity for the conversion of CO to CO in an aqueous electrolyte solution with a positive onset potential of +0.3 V Ag/AgCl, which is 0.

Photoelectrochemical Reduction of CO Coupled to Water Oxidation Using a Photocathode with a Ru(II)-Re(I) Complex Photocatalyst and a CoO/TaON Photoanode.

Photoelectrochemical CO reduction activity of a hybrid photocathode, based on a Ru(II)-Re(I) supramolecular metal complex photocatalyst immobilized on a NiO electrode (NiO-RuRe), was confirmed in an aqueous electrolyte solution. Under half-reaction conditions, the NiO-RuRe photocathode generated CO with high selectivity, and its turnover number for CO formation reached 32 based on the amount of immobilized RuRe. A photoelectrochemical cell comprising a NiO-RuRe photocathode and a CoO/TaON photoanode showed activity for visible-light-driven CO reduction using water as a reductant to generate CO and O, with the assistance of an external electrical (0.

Solar Water Oxidation by Multicomponent TaON Photoanodes Functionalized with Nickel Oxide.

Efficient solar-powered water oxidation over the TaON-based anodes requires coupling this photoactive n-type semiconductor to an electrooxidation catalyst to improve the otherwise unsatisfactory activity and stability. Herein, we examine how functionalization with electrodeposited nickel oxide, NiO , affects the performance of screen-printed TaON photoanodes post-necked with titania (TiO -TaON). The effects of the NiO photo-electrodeposition parameters on the microstructure and photocatalytic performance of the resulting anodes are explored.

Low-Temperature Synthesis of Bismuth Chalcohalides: Candidate Photovoltaic Materials with Easily, Continuously Controllable Band gap.

Although bismuth chalcohalides, such as BiSI and BiSeI, have been recently attracting considerable attention as photovoltaic materials, the methods available to synthesize them are quite limited thus far. In this study, a novel, facile method to synthesize these chalcohalides, including BiSBr1-xIx solid solutions, at low temperatures was developed via the substitution of anions from O(2-) to S(2-) (or Se(2-)) using bismuth oxyhalide precursors. Complete phase transition was readily observed upon treatment of BiOI particles with H2S or H2Se at surprisingly low temperatures of less than 150 °C and short reaction times of less than 1 h, producing BiSI and BiSeI particles, respectively.

Manganese-Substituted Polyoxometalate as an Effective Shuttle Redox Mediator in Z-Scheme Water Splitting under Visible Light.

In the present study, a polyoxometalate is for the first time applied as a shuttle redox in two-step (Z-Scheme) photocatalytic water splitting. Photocatalytic H2 evolution using a Mn-substituted polyoxometalate [SiW11 O39 Mn(II) (H2 O)](6-) as an electron donor proceeded over a Ru-loaded SrTiO3 :Rh photocatalyst under visible light with relatively high selectivity, accompanied by the stoichiometric production of its oxidized form [SiW11 O39 Mn(III) (H2 O)](5-) . Photocatalytic O2 evolution using the oxidized [SiW11 O39 Mn(III) (H2 O)](5-) as an electron acceptor proceeded over PtOx -loaded WO3 photocatalyst under visible light with relatively high quantum efficiency and selectivity, whereas the loading of effective PtOx cocatalyst was necessary to facilitate the reduction of polyoxometalate.

Layered Perovskite Oxychloride Bi4NbO8Cl: A Stable Visible Light Responsive Photocatalyst for Water Splitting.

Mixed anion compounds are expected to be a photocatalyst for visible light-induced water splitting, but the available materials have been almost limited to oxynitrides. Here, we show that an oxychrolide Bi4NbO8Cl, a single layer Sillen-Aurivillius perovskite, is a stable and efficient O2-evolving photocatalyst under visible light, enabling a Z-scheme overall water splitting by coupling with a H2-evolving photocatalyst (Rh-doped SrTiO3). It is found that the valence band maximum of Bi4NbO8Cl is unusually high owing to highly dispersive O-2p orbitals (not Cl-3p orbitals), affording the narrow band gap and possibly the stability against water oxidation.

Photoelectrochemical CO2 reduction using a Ru(II)-Re(I) multinuclear metal complex on a p-type semiconducting NiO electrode.

A photocathode for CO2 reduction was successfully developed using a hybrid electrode comprising a Ru(II)-Re(I) supramolecular photocatalyst and a NiO electrode. Selective photoexcitation of the Ru photosensitizer unit of the photocatalyst at -1.2 V vs.

MnTaO2N: polar LiNbO3-type oxynitride with a helical spin order.

The synthesis, structure, and magnetic properties of a polar and magnetic oxynitride MnTaO2N are reported. High-pressure synthesis at 6 GPa and 1400 °C allows for the stabilization of a high-density structure containing middle-to-late transition metals. Synchrotron X-ray and neutron diffraction studies revealed that MnTaO2N adopts the LiNbO3-type structure, with a random distribution of O(2-) and N(3-) anions.

Fabrication of an efficient BaTaO2N photoanode harvesting a wide range of visible light for water splitting.

Photoanodes made from BaTaO2N that can harvest visible light up to 660 nm wavelength were fabricated on Ti substrates for achieving efficient water splitting. Both pre-treatment of BaTaO2N particles with an H2 stream and post-necking treatment with TaCl5 effectively increased the photocurrent due to the decreased electrical resistance in the porous BaTaO2N photoanode. A combination of pre-loading of CoO(x) on the BaTaO2N particles and post-loading of RhO(x) significantly improved both the photocurrent and stability under visible light irradiation, along with an obvious negative shift (ca.

Highly stable water splitting on oxynitride TaON photoanode system under visible light irradiation.

Highly stable photoelectrochemical water splitting is demonstrated for the first time on a tantalum oxynitride (TaON) photoanode under visible light irradiation. Highly dispersed CoO(x) nanoparticles on the TaON photoanode efficiently scavenge photogenerated holes and effectively suppress self-oxidative deactivation of the TaON surface, resulting in a stable photocurrent. The use of highly dispersed CoO(x) cocatalyst on TaON together with phosphate solutions significantly increased the photocurrent due to the formation of a cobalt/phosphate phase.

SrNbO2N as a water-splitting photoanode with a wide visible-light absorption band.

Strontium niobium oxynitride (SrNbO(2)N) particles were coated on fluorine-doped tin oxide (FTO) glass and examined as a photoelectrode for water splitting under visible light in a neutral aqueous solution (Na(2)SO(4), pH ≈ 6). SrNbO(2)N, which has a band gap of ca. 1.

Overall water splitting under visible light through a two-step photoexcitation between TaON and WO3 in the presence of an iodate-iodide shuttle redox mediator.

A two-step, photocatalytic water splitting system consisting of Pt-loaded TaON (a H(2) evolution photocatalyst), Pt-loaded WO(3) (an O(2) evolution photocatalyst), and an iodate-iodide (IO(3)(-)/I(-)) shuttle redox mediator is investigated under visible light irradiation. Photocatalytic oxidation of water to O(2) and reduction of IO(3)(-) to I(-) proceeded with good selectivity over the Pt-WO(3) photocatalyst, even in the presence of a considerable amount of I(-) anions in the solution. The key difference between the adsorption properties of IO(3)(-) and I(-) anions on WO(3) strongly suggested that the photoexcited electrons could react efficiently with IO(3)(-) adsorbed on WO(3), whereas the photogenerated holes selectively reacted with water molecules owing to the low adsorptivity of I(-) on WO(3).

Modified Ta3N5 powder as a photocatalyst for O2 evolution in a two-step water splitting system with an iodate/iodide shuttle redox mediator under visible light.

Modification of tantalum nitride (Ta(3)N(5)), which has a band gap of 2.1 eV, with nanoparticulate iridium (Ir) and rutile titania (R-TiO(2)) achieved functionality as an O(2) evolution photocatalyst in a two-step water-splitting system with an IO(3)(-)/I(-) shuttle redox mediator under visible light (lambda > 420 nm) in combination with a Pt/ZrO(2)/TaON H(2) evolution photocatalyst. The loaded Ir nanoparticles acted as active sites to reduce IO(3)(-) to I(-), while the R-TiO(2) modifier suppressed the adsorption of I(-) on Ta(3)N(5), allowing Ta(3)N(5) to evolve O(2) in the two-step water-splitting system.

Facile fabrication of an efficient oxynitride TaON photoanode for overall water splitting into H2 and O2 under visible light irradiation.

The porous oxynitride TaON film electrode prepared on conducting glass (FTO) showed significantly high quantum efficiency (IPCE = ca. 76% at 400 nm at 0.6 V vs Ag/AgCl) in an aqueous Na(2)SO(4) solution, after loading of IrO(2) x nH(2)O nanoparticles as a cocatalyst for water oxidation.

Efficient nonsacrificial water splitting through two-step photoexcitation by visible light using a modified oxynitride as a hydrogen evolution photocatalyst.

A two-step photocatalytic water splitting (Z-scheme) system consisting of a modified ZrO(2)/TaON species (H(2) evolution photocatalyst), an O(2) evolution photocatalyst, and a reversible donor/acceptor pair (i.e., redox mediator) was investigated.

Photocatalytic activity of R3MO7 and R2Ti2O7 (R=Y, Gd, La; M=Nb, Ta) for water splitting into H2 and O2.

The photocatalytic activities of R3MO7 and R2Ti2O7 (R=Y, Gd, La; M=Nb, Ta) strongly depended on the crystal structure. Overall, photocatalytic water splitting into H2 and O2 proceeded over La3TaO7 and La3NbO7, which have an orthorhombic weberite structure, Y2Ti2O7 and Gd2Ti2O7, which have a cubic pyrochlore structure, and La2Ti2O7, which has a monoclinic perovskite structure. All of these materials are composed of a network of corner-shared octahedral units of metal cations (TaO6, NbO6, or TiO6); materials without such a network were inactive.