Shicheng Yan

High-Yield Synthesis of Ultralong and Ultrathin Zn2GeO4 Nanoribbons toward Improved Photocatalytic Reduction of CO2 into Renewable Hydrocarbon Fuel

Single-crystalline Zn(2)GeO(4) nanobelts with lengths of hundreds of micrometers, thicknesses as small as ∼7 nm, and aspect ratios of up to 10,000 were synthesized in a binary ethylenediamine/water solvent system using a solvothermal route. The ultralong and ultrathin geometry of the Zn(2)GeO(4) nanoribbon proves to greatly promote the photocatalytic activity toward reduction of CO(2) into renewable hydrocarbon fuel (CH(4)) in the presence of water vapor.

Solar hydrogen generation from seawater with a modified BiVO4 photoanode

Hydrogen is a very promising candidate as a future energy carrier. It is attractive to produce hydrogen from solar energy and seawater, the most abundant renewable energy source and the most abundant natural resource on the earth. To date, there is no report on a stable photoelectrode with a high incident photon conversion efficiency (IPCE) in seawater splitting under irradiation by visible light. Herein, we report an efficient and stable system for seawater splitting based on a multi-metal oxide BiVO4 after modification. The results indicated that modified BiVO4 had a photocurrent density of 2.16 mA cm−2 at 1.0 VRHE in natural seawater under AM 1.5G sunlight (1000 W m−2) and exhibited the highest IPCE at 1.0 VRHE in the visible light region of 440–480 nm among all known oxide photoanodes.

High-Yield Synthesis of Ultrathin and Uniform Bi2WO6 Square Nanoplates Benefitting from Photocatalytic Reduction of CO2 into Renewable Hydrocarbon Fuel under Visible Light

Ultrathin and uniform Bi(2)WO(6) square nanoplates of ∼9.5 nm thickness corresponding to six repeating cell units were prepared in the presence of oleylamine using a hydrothermal route. The Bi(2)WO(6) nanoplates show great potential in the utilization of visible light energy to the highly efficient reduction of CO(2) into a renewable hydrocarbon fuel. On the one hand, the ultrathin geometry of the nanoplates promotes charge carriers to move rapidly from the interior to the surface to participate in the photoreduction reaction. This should also favor the improved separation of photogenerated electron and hole and a lower electron-hole recombination rate; on the other hand, the Bi(2)WO(6) square nanoplate is proven to provide the well-defined {001} facet for two dominantly exposed surfaces, which is a prerequisite for the high level of photocatalytic activity of CO(2) fixation.

Facile temperature-controlled synthesis of hexagonal Zn2GeO4 nanorods with different aspect ratios toward improved photocatalytic activity for overall water splitting and photoreduction of CO2

Single-crystalline hexagonal prism Zn(2)GeO(4) nanorods with different aspect ratios have been prepared via a solution phase route, which exhibits improved photocatalytic activities in overall water splitting and photoreduction of CO(2) due to the low crystal defects, high specific surface area and beneficial microstructure on the catalysts surface.

Sol–gel hydrothermal synthesis of visible-light-driven Cr-doped SrTiO3 for efficient hydrogen production

Using a sol–gel hydrothermal method, we have synthesized Cr-doped SrTiO3 with a high specific surface area (19.3–65.4 m2 g−1, depending on the hydrothermal temperature). X-ray diffraction (XRD), UV-Vis diffuse reflectance spectra, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were used to investigate the Cr-doped SrTiO3. XRD analysis showed that Cr-doped SrTiO3 exhibited good crystallinity and the crystalline size calculated using Scherrer equation is about 20–30 nm. UV-Vis diffuse reflectance spectra showed that Cr doping can extend the absorption edge of SrTiO3 into visible region (540 nm). TEM images of Cr-doped SrTiO3 showed that the high temperature during the hydrothermal reaction will prompt the aggregation of primary particles into porous spheres. The porous structure was further certified by nitrogen physisorption results. By loading Pt (0.6 wt.%) nanoparticles as a cocatalyst, the as-prepared Cr-doped SrTiO3 photocatalyst exhibited high H2 evolution rate (82.6 μmol h−1) from 20% methanol solution under visible light irradiation, which is 3 times higher than that of the sample synthesized by solid state reaction. The high activity of the as-prepared Cr-doped SrTiO3 can be attributed to the high specific surface area and good crystallinity.

Single-Crystalline, Ultrathin ZnGa2O4 Nanosheet Scaffolds To Promote Photocatalytic Activity in CO2 Reduction into Methane

Uniform hierarchical microspheres scaffolded from ultrathin ZnGa2O4 nanosheets with over 99% exposed facets were synthesized using an easy solvothermal route with ethylenediamine (en)/H2O binary solvents. Substitution of different chain length amines for en results in no formation of the nanosheet structures, indicating that the molecular structure of En is indispensable for the generation of two-dimensional structures. Inheriting both a high surface area of nanosheets and a high crystallinity of bulky materials allows the unique 3D hierarchical nanostructures to possess great CO2 photocatalytic performance. The normalized time-resolved traces of photo-induced absorption recorded from the nanosheet and meso-ZnGa2O4 indicate that the photo-excited carriers can survive longer on the nanosheet, which also contributes to the high photocatalytic activity of the ZnGa2O4 nanosheets.

Facile synthesis of anatase TiO2 mesocrystal sheets with dominant {001} facets based on topochemical conversion

Uniform anatase TiO2 mesocrystal sheets with dominant {001} facets were synthesized via a self-assembly and self-etching surfactant-free solvothermal process. The formation of well-faceted square sheets can be ascribed to the highly oriented assemblies of building blocks, while the etching agent HF also plays an important role in the tailored synthesis. During the topochemical conversion from NH4TiOF3 to TiO2, a shrinkage void was generated, and the reason proposed is based on the crystal structural differences. Calcination leads to a more observable porous structure but the original shape is well retained. Smaller sheets can be simply obtained by substituting ethanol with 2-propanol which behaves as a synergistic capping agent.

A simple and efficient strategy for the synthesis of a chemically tailored g-C3N4 material

Tailored nanostructures offer a new way to facilitate electron–hole separation and offer additional opportunities to generate unique photocatalysts that demonstrate novel light absorption, thermodynamic and kinetic properties. A simple and efficient approach to the synthesis of a large variety of g-C3N4 tailored nanostructures is reported. Herein, NH3 and H2O2 were used as controllable chemical scissors to tailor bulk g-C3N4 to a large variety of g-C3N4 nanostructures, which include exfoliated porous, quantum dot, nanomites and nanospindles. The tailored g-C3N4 shows a photoreactivity of H2 evolution 3.0 (pure water) and 4.1 (saturated KCl solution) times higher than bulk g-C3N4 under λ > 420 nm. We believe this strategy affords new opportunities for structural tuning of X-doped (X = N, S, P, and O) carbon materials, as well as their exploration in catalysis, organic synthesis, nanomedicine and energy storage.

BiVO4 nano–leaves: Mild synthesis and improved photocatalytic activity for O2 production under visible light irradiation

Nano-leaf bismuth vanadate (BiVO4), which acts as an active photocatalyst for O2 evolution under visible light irradiation, was synthesized by a wet chemical method. The BiVO4 photocatalyst was obtained by the reaction of Bi(NO3)3·5H2O and NH4VO3 at a low temperature (60 °C). Both the morphology and the crystal phase of the synthesized product can be tuned by changing the concentrations of the precursor. The O2 evolution activity of BiVO4 nano-leaves from photocatalytic water splitting under visible light irradiation ( λ >420 nm) is significantly higher than that of the BiVO4 sample synthesized by a traditional solid state reaction method, and the activity can be further improved by annealing the samples.

ZnO plates synthesized from the ammonium zinc nitrate hydroxide precursor

ZnO assembled hexagonal or porous rectangular plates were synthesized from the decomposition of a new precursor, ammonium zinc nitrate hydroxide (NH4Zn3(OH)6NO3), through a facile solvothermal route assisted by Poly(styrene sulfonic acid) sodium salt (PSS). XRD, BET surface area measurements, SEM, HRTEM and TG-DSC were used to describe the as-prepared products and understand the phase transformation. Our results indicate that the morphology of the ZnO plates is dependent strongly on the decomposition process of the precursor. By directly heating NH4Zn3(OH)6NO3, porous ZnO plates were obtained due to the thermal decomposition of the precursor. Using the same precursor under the solvothermal reaction, however, the final product is hexagonal ZnO plates. The growth mechanism of ZnO plates formed in different synthetic routes was proposed. Photoluminescence (PL) and photocatalytic properties of the as-prepared ZnO with different morphologies were studied. Porous ZnO plates showed three emission peaks, which may be induced by its microstructure and defect centres, and the porous ZnO showed the improved photocatalytic activity for photoreduction of CO2.