Synthesis of meso-porous α-GaO from liquid Ga metal having significantly high photocatalytic activity for CO reduction with water.

We have succeeded in synthesizing meso-porous α-GaO which shows significantly high photocatalytic activity for CO reduction with water. The sample was synthesized by hydroxidation of liquid Ga metal in water to obtain GaOOH and Ga(OH), followed by the calcination of the mixed hydroxides at 773 K for 1 hour which converted them to meso-porous α-GaO. The nano-pores remained as the trace of the evaporation of water produced by the oxidation of the hydroxides during the calcination.

Influence of Ag Clusters on the Electronic Structures of β-GaO Photocatalyst Surfaces.

In order to understand the photocatalytic carbon dioxide reduction over Ag-loaded β-GaO photocatalysts, first principles calculations based on density functional theory were performed on the surface model of a Ag cluster-adsorbed β-GaO system. The stable adsorption structures of Ag ( = 1 to 4) clusters on the β-GaO (100) surface were determined. In the electronic structure analysis, the valence states of all Ag clusters mixed with the top of the O 2p valence band of GaO, leading the Fermi level of Ag /β-GaO to shift to the bottom of the conduction band.

Synthesis of α-GaO by Water Oxidation of Metallic Gallium as a Photocatalyst for CO Reduction with Water.

We have succeeded to synthesize gallium oxide consisting of α-phase (α-GaO) with the calcination of GaOOH obtained by a direct reaction of liquid Ga metal with water for the first time and found that α-GaO exhibits photocatalytic activity for CO reduction with water and water splitting as well. The calcination above 623 K converted GaOOH to α-GaO, and the samples calcined at 723-823 K were well crystallized to α-GaO and promoted photocatalytic CO reduction with water, producing CO, H, and O. This is observed for the first time that α-GaO without a cocatalyst has shown very high photocatalytic activity for the conversion of CO to CO.

Comparison of platinum photodeposition processes on two types of titanium dioxide photocatalysts.

The photodeposition method is useful for the preparation of metal-loaded photocatalysts, by which the metal precursors are adsorbed on the photocatalyst surface and reduced by photoexcited electrons to typically form metallic nanoparticles. In the present study, the photodeposition process of Pt nanoparticles was investigated on anatase and rutile TiO2 photocatalysts. It was found that on the anatase surface, only some of the Pt4+ precursors were first adsorbed in an adsorption equilibrium and reduced to form a smaller number of initial metal species; then, they functioned as electron receivers to reduce the remaining precursors on their metallic surfaces and become larger particles.

TiO N /TiO Photocatalyst for Hydrogen Evolution under Visible Light Irradiation II Degradation of Photocatalytic Activity of TiO N /TiO with Mild Oxidation.

We have studied degradation of photocatalytic activity of TiO N for water splitting under visible light irradiation with heat treatment in O/N mixed gas. The reduction of the N content by oxidation through the formation of O-N-O species (NO ) was confirmed as the result of the reduction of the catalytic activity. The catalytic activity is not simply related to the amount of N remained but that of N taking the chemical state of O-Ti-N in TiO N , which is the active species for visible light responsiveness on hydrogen evolution.

TiO N /TiO Photocatalyst for Hydrogen Evolution under Visible-Light Irradiation. I: Characterization of N in TiO N /TiO Photocatalyst.

TiO N /TiO was synthesized by nitriding of TiO in NH gas. TiO N /TiO generated hydrogen from methanol aqueous solution under visible-light irradiation. It was revealed by N K-edge XANES and N 1s XPS measurements that the N species contributing to visible-light responsiveness was the O-Ti-N species.

Photocatalytic Activity of GaO Supported on AlO for Water Splitting and CO Reduction.

We have examined the photocatalytic activity of GaO supported on AlO (GaO/AlO catalyst) without a noble metal cocatalyst for water splitting and reduction of CO with water under UV light irradiation by changing the loading amount of GaO. All prepared GaO/AlO catalysts show photocatalytic activities for both water splitting and CO reduction, and their activities are significantly improved compared to those of nonsupported GaO and AlO. The water splitting is dominated for GaO/AlO with less than 1.

Realization of red shift of absorption spectra using optical near-field effect.

In many applications such as CO reduction and water splitting, high-energy photons in the ultraviolet region are required to complete the chemical reactions. However, to realize sustainable development, the photon energies utilized must be lower than the absorption edge of the materials including the metal complex for CO reduction, the electrodes for water splitting, because of the huge amount of lower energy than the visible region received from the sun. In the previous works, we had demonstrated that optical near-fields (ONFs) could realize chemical reactions, by utilizing photon energies much lower than the absorption edge because of the spatial non-uniformity of the electric field.

Robust Binding between Carbon Nitride Nanosheets and a Binuclear Ruthenium(II) Complex Enabling Durable, Selective CO Reduction under Visible Light in Aqueous Solution.

Carbon nitride nanosheets (NS-C N ) were found to undergo robust binding with a binuclear ruthenium(II) complex (RuRu') even in basic aqueous solution. A hybrid material consisting of NS-C N (further modified with nanoparticulate Ag) and RuRu' promoted the photocatalytic reduction of CO to formate in aqueous media, in conjunction with high selectivity (approximately 98 %) and a good turnover number (>2000 with respect to the loaded Ru complex). These represent the highest values yet reported for a powder-based photocatalytic system during CO reduction under visible light in an aqueous environment.

Effective nitrogen doping into TiO2 (N-TiO2) for visible light response photocatalysis.

The thickness-controlled TiO2 thin films are fabricated by the pulsed laser deposition (PLD) method. These samples function as photocatalysts under UV light irradiation and the reaction rate depends on the TiO2 thickness, i.e.