Near-infrared light-inducible Z-scheme overall water-splitting photocatalyst without an electron mediator.

We facilely prepared a solid-state heterojunction photocatalyst in which silver vanadium oxide (AgVO) and zinc rhodium oxide (ZnRhO) as oxygen and hydrogen evolution photocatalysts, respectively, were directly connected to generate AgVO/ZnRhO. AgVO/ZnRhO photocatalyzed overall pure-water splitting without any electron mediator under irradiation with near-infrared light at wavelengths of up to 910 nm. The key points are that the conduction bottom potential of AgVO is almost the same as the valence band top potential of ZnRhO, and that the bandgaps of AgVO and ZnRhO are 1.

Red light-inducible overall water-splitting photocatalyst, gold-inserted zinc rhodium oxide and bismuth vanadium oxide heterojunction, connected using gold prepared by sputtering in ionic liquid.

We prepared a solid-state Z-scheme photocatalyst in which zinc rhodium oxide (ZnRhO) and bismuth vanadium oxide (BiVO) that served as hydrogen (H) and oxygen (O) evolution photocatalysts, respectively, were connected with gold (Au) nanoparticles. The Au nanoparticles were prepared by sputtering in an ionic liquid, N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide, to generate Au/ZnRhO/Au/BiVO with various amounts of Au in the 12 mol. %-29 mol.

Selective loading of platinum or silver cocatalyst onto a hydrogen-evolution photocatalyst in a silver-mediated all solid-state Z-scheme system for enhanced overall water splitting.

We selectively loaded a hydrogen (H)-evolution cocatalyst, either platinum (Pt) or silver (Ag), onto a H-evolution photocatalyst, zinc rhodium oxide (ZnRhO), in a Ag-inserted ZnRhO and bismuth vanadium oxide (BiVO) hetero-junction photocatalyst (ZnRhO/Ag/BiVO) by a photo-deposition method. The selective loading of Pt or Ag was achieved by taking advantage of the band-gap difference between ZnRhO (1.2 eV) and BiVO (1.

Preparation of Polyoxometalate-based Photo-responsive Membranes for the Photo-activation of Manganese Oxide Catalysts.

This paper presents a method to prepare charge-transfer chromophores using polyoxotungstate (PW12O40), transition metal ions (Ce or Co), and organic polymers, with the aim of photo-activating oxygen-evolving manganese oxide catalysts, which are important components in artificial photosynthesis. The cross-linking technique was applied to obtain a self-standing membrane with a high PW12O40 content. Incorporation and structure retention of PW12O40 within the polymer matrix were confirmed by FT-IR and micro-Raman spectroscopy, and optical characteristics were investigated by UV-Vis spectroscopy, which revealed successful construction of the metal-to-metal charge transfer (MMCT) unit.

Facile synthesis of a red light-inducible overall water-splitting photocatalyst using gold as a solid-state electron mediator.

We facilely prepared a solid-state heterojunction photocatalyst in which zinc rhodium oxide (ZnRh2O4) and bismuth vanadium oxide (Bi4V2O11) as hydrogen (H2) and oxygen (O2) evolution photocatalysts, respectively, were connected with gold (Au) to generate ZnRh2O4/Au/Bi4V2O11. ZnRh2O4/Au/Bi4V2O11 photocatalyzed the overall pure-water splitting under irradiation with red light at wavelengths of up to 740 nm.

Element strategy of oxygen evolution electrocatalysis based on in situ spectroelectrochemistry.

Oxygen evolution electrocatalysis has received extensive attention due to its significance in biology, chemistry, and technology. However, it is still unclear how the abundant 3d-elements can be used to drive the four-electron oxidation of water as efficiently as in Nature. In this Feature Article, we will propose a design strategy concerning the optimization of the charge accumulation process based on our ongoing spectroelectrochemical study on Mn, Fe, and Ir oxygen evolution catalysts.

Efficient oxygen evolution on hematite at neutral pH enabled by proton-coupled electron transfer.

The rate-determining step of the oxygen evolution reaction on hematite electrodes was switched from the sequential electron/proton transfer process to the concerted proton-coupled electron transfer (CPET) process by adding pyridine derivatives to the electrolyte. By inducing the CPET process, the overpotential for oxygen evolution at neutral pH decreased by approximately 250 mV.

A heterojunction photocatalyst composed of zinc rhodium oxide, single crystal-derived bismuth vanadium oxide, and silver for overall pure-water splitting under visible light up to 740 nm.

We recently reported the synthesis of a solid-state heterojunction photocatalyst consisting of zinc rhodium oxide (ZnRhO) and bismuth vanadium oxide (BiVO), which functioned as hydrogen (H) and oxygen (O) evolution photocatalysts, respectively, connected with silver (Ag). Polycrystalline BiVO (p-BiVO) powders were utilized to form ZnRhO/Ag/p-BiVO, which was able to photocatalyze overall pure-water splitting under red-light irradiation with a wavelength of 700 nm (R. Kobayashi et al.

Development of optically transparent water oxidation catalysts using manganese pyrophosphate compounds.

One challenge in artificial photosynthetic systems is the development of active oxygen evolution catalysts composed of abundant elements. The oxygen evolution activities of manganese pyrophosphate compounds were examined in electrochemical and photochemical experiments. Electrocatalysis using calcium-manganese pyrophosphate exhibited good catalytic ability under neutral pH and an oxygen evolution reaction was driven with a small overpotential (η<100 mV).

Photocatalytic hydrogen evolution over β-iron silicide under infrared-light irradiation.

We investigated the ability of β-iron silicide (β-FeSi2) to serve as a hydrogen (H2)-evolution photocatalyst due to the potential of its conduction band bottom, which may allow thermodynamically favorable H2 evolution in spite of its small band-gap of 0.80 eV. β-FeSi2 had an apparent quantum efficiency for H2 evolution of ∼24% up to 950 nm (near infrared light), in the presence of the dithionic acid ion (S2O6(2-)) as a sacrificial agent.

Regulating proton-coupled electron transfer for efficient water splitting by manganese oxides at neutral pH.

Manganese oxides have been extensively investigated as model systems for the oxygen-evolving complex of photosystem II. However, most bioinspired catalysts are inefficient at neutral pH and functional similarity to the oxygen-evolving complex has been rarely achieved with manganese. Here we report the regulation of proton-coupled electron transfer involved in water oxidation by manganese oxides.

Inhibition of charge disproportionation of MnO2 electrocatalysts for efficient water oxidation under neutral conditions.

The development of Mn-oxide electrocatalysts for the oxidation of H(2)O to O(2) has been the subject of intensive researches not only for their importance as components of artificial photosynthetic systems, but also as O(2)-evolving centers in photosystem II. However, limited knowledge of the mechanisms underlying this oxidation reaction hampers the ability to rationally design effective catalysts. Herein, using in situ spectroelectrochemical techniques, we demonstrate that the stabilization of surface-associated intermediate Mn(3+) species relative to charge disproportionation is an effective strategy to lower the overpotential for water oxidation by MnO(2).

Multielectron-transfer reactions at single Cu(II) centers embedded in polyoxotungstates driven by photo-induced metal-to-metal charge transfer from anchored Ce(III) to framework W(VI).

Using carbon monoxide as a probe molecule for the oxidation state of Cu ions, we demonstrated that anchored polynuclear charge-transfer complexes consisting of Ce(III) ions and Cu(II)-substituted Keggin-type polyoxotungstates function as efficient visible-light-driven multielectron-transfer catalysts.

Mechanisms of pH-dependent activity for water oxidation to molecular oxygen by MnO2 electrocatalysts.

Manganese oxides function as efficient electrocatalysts for water oxidation to molecular oxygen in strongly alkaline conditions, but are inefficient at neutral pH. To provide new insight into the mechanism underlying the pH-dependent activity of the electrooxidation reaction, we performed UV-vis spectroelectrochemical detection of the intermediate species for water oxidation by a manganese oxide electrode. Layered manganese oxide nanoparticles, δ-MnO(2) (K(0.