NanoCOT: Low-Cost Nanostructured Electrode Containing Carbon, Oxygen, and Titanium for Efficient Oxygen Evolution Reaction.

Developing high-efficiency, durable, and low-cost catalysts based on earth-abundant elements for the oxygen evolution reaction (OER) is essential for renewable energy conversion and energy storage devices. In this study, we report a highly active nanostructured electrode, NanoCOT, which contains carbon, oxygen, and titanium, for efficient OER in alkaline solution. The NanoCOT electrode is synthesized from carbon transformation of TiO2 in an atmosphere of methane, hydrogen, and nitrogen at a high temperature. The NanoCOT exhibits enhanced OER catalytic activity in alkaline solution, providing a current density of 1.33 mA/cm(2) at an overpotential of 0.42 V. This OER current density of a NanoCOT electrode is about 4 times higher than an oxidized Ir electrode and 15 times higher than a Pt electrode because of its nanostructured high surface area and favorable OER kinetics. The enhanced catalytic activity of NanoCOT is attributed to the presence of a continuous energy band of the titanium oxide electrode with predominantly reduced defect states of Ti (e.g., Ti(1+), Ti(2+), and Ti(3+)) formed by chemical reduction with hydrogen and carbon. The OER performance of NanoCOT can also be further enhanced by decreasing its overpotential by 150 mV at a current density of 1.0 mA/cm(2) after coating its surface electrophoretically with 2.0 nm IrOx nanoparticles.

Visible light driven photoelectrochemical properties of Ti@TiO2 nanowire electrodes sensitized with core-shell Ag@Ag2S nanoparticles.

We present a model electrode system comprised of nanostructured Ti electrode sensitized with Ag@Ag2S core-shell nanoparticles (NPs) for visible light driven photoelectrochemistry studies. The nanostructured Ti electrode is coated with Ti@TiO2 nanowires (NW) to provide a high surface area for improved light absorption and efficient charge collection from the Ag@Ag2S NPs. Pronounced photoelectrochemical responses of Ag@Ag2S NPs under visible light were obtained and attributed to collective contributions of visible light sensitivity of Ag2S, the local field enhancement of Ag surface plasmon, enhanced charge collection by Ti@TiO2 NWs, and the high surface area of the nanostructured electrode system. The shell thickness and core size of the Ag@Ag2S core-shell structure can be controlled to achieve optimal photoelectrochemical performance. XPS, XRD, SEM, high resolution TEM, AC impedance, and other electrochemical methods are applied to resolve the structure-function relationship of the nanostructured Ag@Ag2S NP electrode.

Resin-derived hierarchical porous carbon spheres with high catalytic performance in the oxidative dehydrogenation of ethylbenzene.

Pre-shaped hierarchical porous carbon (HPC) spheres have been synthesized through a facile anion exchanged route. An industrial polymeric anion-exchange resin with a hierarchical pore structure was used as the carbon precursor. Its high porosity was conserved using an aluminate/silicate precursor forming a hard support to prevent the structural collapse during the carbonization process. Physicochemical bulk and surface properties of the obtained HPC spheres were characterized by X-ray diffraction, scanning and transmission electron microscopy, N(2) physisorption, and X-ray photoemission spectroscopy. Results obtained indicate that HPC keeps the abundant hierarchical porosity including meso- and macropores as well as the high surface area of the resin precursor. The as-synthesized HPC spheres were tested as a catalyst for oxidative dehydrogenation of ethylbenzene to styrene. The oxygen-rich catalyst surface formed under reaction conditions shows a high catalytic performance and stability, making HPC to a potential catalyst for this type of reaction.

Quasi-linear dependence of cation filling on the photocatalysis of A(x)BO3-based tunnel compounds.

A series of A(x)BO(3)-based oxides, (A1)(4)(A2)(2)(A3)(4)Nb(10)O(30) (A1 = Sr, Ba; A2 = Na, K; A3 = □) as deficient perovskites, ATiO(3) (A = Mg, Ca, Sr, Ba) as ideal perovskites are prepared by solid-state reaction method, and investigated as novel tunnel photocatalysts. The efficiency exhibits a high dependence on the cation filling in the respective tunnels of these compounds. Generally, lower cation filling contributes to a higher activity. The cation filling is rationalized by the crystal packing factor (PF), the photocatalytic efficiency decreases quasi-linearly with PF. Moreover, the linear correlation also exists in the literature involving tunnel photocatalysts of Bi(2)RNbO(7) (R = Y, rare earth element), MIn(2)O(4) (M = Ca, Sr, Ba), ATaO(3) (A = Li, Na, K), etc. Such linear correlation of photocatalysis with the crystal structure has not been reported in the literature. The study of structure-modification by controlling cation-filling for improving activity sheds light on the mechanism of photocatalysis and on developing new high-performance photocatalysts.

Designed synthesis of TS-1 crystals with controllable b-oriented length.

TS-1 crystals with controllable b-oriented length (sheet-like morphology, TS-1-S; chain-like morphology, TS-1-C) have been rationally synthesized from addition of organic additives (urea and fluorinated surfactant of FC-4) in the starting titanosilicate gels, and catalytic and adsorptive measurements show that TS-1-S samples are very active in Beckmann rearrangement of cyclohexanone oxime, whereas TS-1-C samples are selective in adsorption for para-xylene.

Novel antimonate photocatalysts MSb2O6 (M = Ca, Sr and Ba): a correlation between packing factor and photocatalytic activity.

Well-crystallized MSb(2)O(6) (M = Ca, Sr and Ba) powders synthesized by solid state reactions exhibit an interesting photocatalytic activity order of Ba > Sr > Ca for organic pollutant (methylene blue and phenol) degradation and hydrogen production from water under UV light irradiation. A simple model, crystal packing factor (PF), was introduced to account for the activity difference. Nine series of photocatalysts involving 26 compounds were experimentally investigated to further substantiate the model, a lower PF being correlated to a higher photocatalytic activity. This correlation between packing factor and photocatalytic activity also holds for some 40 literature examples of 83 compounds of d(0) cations and d(10) cations. This applicable criterion for ranking photocatalytic materials of similar chemistry or structure can be rationalized through the influence of structural packing on carrier lifetimes and mobilities.

One-pot hydrothermal synthesis of mesostructured silica nanotube.

Mesostructured silica nanotubes have been synthesized in a system of carbon nanotubes/cetyltrimethylammonium bromide/tetraethyl orthosilicate/NH(3) x H(2)O through one-pot hydrothermal route. The obtained sample was characterized with X-ray diffraction, nitrogen sorption, scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray techniques. These results indicate mesostructured silica nanotubes exhibit small tube diameters (10-40 nm), uniform mesopores (2.5 nm), and a huge pore volume (1.7 cm(3)/g).

Highly ordered mesoporous carbon as catalyst for oxidative dehydrogenation of ethylbenzene to styrene.

We demonstrate that mesoporous carbon without deposition of metal particles is a highly active catalyst. It exhibits both high activity and selectivity in oxidative dehydrogenation of ethylbenzene to styrene, as well as long catalytic stability when compared with activated carbon. Both the as-prepared mesoporous carbon and the active coke formed during the initial stage of the reaction play an important role in the catalytic performance. XPS and IR techniques reveal that the surface oxygen functional groups formed during the reaction are the active sites for the reaction. The ordered mesoporous structure is beneficial for mass transport in catalytic reaction exhibiting long term stability in contrast to activated carbon.