Zhiqiang Wang

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.

Direct synthesis and characterization of CdS nanobelts

A method to directly synthesize single crystalline CdS nanobelts has been developed. The advantages of the method in rapid synthesis within several minutes and catalyst free comparing to the previous method propose a potential avenue to the further practical device production and applications. The as-synthesized CdS nanobelts grow along the [100] crystalline direction with usually 500–2000nm in width and about tens to several hundred micrometers in length. Two luminescence peaks around 516 and 758nm in room-temperature photoluminescence spectrum are ascribed to the band-to-band and trap emission, respectively.

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.

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.

Unravelling the Role of Electrochemically Active FePO4 Coating by Atomic Layer Deposition for Increased High-Voltage Stability of LiNi0.5Mn1.5O4 Cathode Material

Ultrathin amorphous FePO4 coating derived by atomic layer deposition (ALD) is used to coat the 5 V LiNi0.5Mn1.5O4 cathode material powders, which dramatically increases the capacity retention of LiNi0.5Mn1.5O4. It is believed that the amorphous FePO4 layer could act as a lithium‐ions reservoir and electrochemically active buffer layer during the charge/discharge cycling, helping achieve high capacities in LiNi0.5Mn1.5O4, especially at high current densities.

Fluorescent N-Doped Carbon Dots as in Vitro and in Vivo Nanothermometer

The fluorescent N-doped carbon dots (N-CDs) obtained from C3N4 emit strong blue fluorescence, which is stable with different ionic strengths and time. The fluorescence intensity of N-CDs decreases with the temperature increasing, while it can recover to the initial one with the temperature decreasing. It is an accurate linear response of fluorescence intensity to temperature, which may be attributed to the synergistic effect of abundant oxygen-containing functional groups and hydrogen bonds. Further experiments also demonstrate that N-CDs can serve as effective in vitro and in vivo fluorescence-based nanothermometer.

Synthesis, growth mechanism and photoelectrochemical properties of BiVO4 microcrystal electrodes

BiVO4 films were deposited on fluorine-doped tin oxide substrates by chemical bath deposition. The samples were characterized by an x-ray diffractometer, UV–Vis transmission spectra and a scanning electron microscope. The morphologies of the samples were adjusted by the deposition time, temperature, pH of solution and buffer solution. When the temperature and pH value of the solution were high, the polyhedron microcrystal of BiVO4 exposed fewer less planes on the surface and the films were more compact. On the basis of the experimental results, a possible growth mechanism was proposed. Moreover, the photoelectrochemical properties of the samples with different morphologies were investigated. The results suggested that the compact films with a smaller microcrystal exhibited better performance, which was helpful to understand the relationship between the morphologies of other microcrystal electrodes and their photoelectrochemical properties.

Ge‐Mediated Modification in Ta3N5 Photoelectrodes with Enhanced Charge Transport for Solar Water Splitting

Ta3 N5 is a promising photoanode candidate for photoelectrochemical water splitting, with a band gap of about 2.1u2005eV and a theoretical solar-to-hydrogen efficiency as high as 15.9u2009% under AM 1.5u2005G 100u2005mWu2009cm(-2) irradiation. However, the presently achieved highest photocurrent (ca. 7.5u2005mAu2009cm(-2) ) on Ta3 N5 photoelectrodes under AM 1.5u2005G 100u2005mWu2009cm(-2) is far from the theoretical maximum (ca. 12.9u2005mAu2009cm(-2) ), which is possibly due to serious bulk recombination (poor bulk charge transport and charge separation) in Ta3 N5 photoelectrodes. In this study, we show that volatilization of intentionally added Ge (5u2009%) during the synthesis of Ta3 N5 promotes the electron transport and thereby improves the charge-separation efficiency in bulk Ta3 N5 photoanode, which affords a 320u2009% increase of the highest photocurrent comparing with that of pure Ta3 N5 photoanode under AM 1.5u2005G 100u2005mWu2009cm(-2) simulated sunlight.

Hydroxyapatite−TiO 2 ‑based Nanocomposites Synthesized in Supercritical CO 2 for Bone Tissue Engineering: Physical and Mechanical Properties

Calcium phosphate-based nanocomposites offer a unique solution toward producing scaffolds for orthopedic and dental implants. However, despite attractive bioactivity and biocompatibility, hydroxyapatite (HAp) has been limited in heavy load-bearing applications due to its intrinsically low mechanical strength. In this work, to improve the mechanical properties of HAp, we grew HAp nanoplates from the surface of one-dimensional titania nanorod structures by combining a coprecipitation and sol-gel methodology using supercritical fluid processing with carbon dioxide (scCO2). The effects of metal alkoxide concentration (1.1-1.5 mol/L), reaction temperature (60-80 °C), and pressure (6000-8000 psi) on the morphology, crystallinity, and surface area of the resulting nanostructured composites were examined using scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), and Brunauer-Emmet-Teller (BET) method. Chemical composition of the products was characterized using Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray absorption near-edge structure (XANES) analyses. HAp nanoplates and HAp-TiO2 nanocomposites were homogeneously mixed within poly(ε-caprolactone) (PCL) to develop scaffolds with enhanced physical and mechanical properties for bone regeneration. Mechanical behavior analysis demonstrated that the Youngs and flexural moduli of the PCL/HAp-TiO2 composites were substantially higher than the PCL/HAp composites. Therefore, this new synthesis methodology in scCO2 holds promise for bone tissue engineering with improved mechanical properties.

Two-step reactive template route to a mesoporous ZnGaNO solid solution for improved photocatalytic performance

A mesoporous ZnGaNO photocatalyst was synthesized by nitriding the mesoporous nanocrystalline ZnGa2O4 oxide precursor at a low temperature of 680 °C. The as-prepared ZnGaNO photocatalyst exhibits an improved photocatalytic activity in photodegrading IPA due to strong gas absorption by the mesostructure and extended light absorption by the high Zn content.