Bizhou Lin

Enhanced photocatalytic H2 evolution on ZnS loaded with graphene and MoS2 nanosheets as cocatalysts

Graphene and MoS2 nanosheets modified ZnS nanoparticles were successfully prepared by a simple one-pot hydrothermal route in the presence of graphene and MoS2 nanosheets. The resultant ZnS/graphene/MoS2 nanocomposites exhibited significantly enhanced photocatalytic activity and good recurrence stability in H2 evolution from water splitting. When the loading content of graphene was 0.25 wt% and that of MoS2 was 2 atom%, the ZnS/graphene/MoS2 nanocomposite reached a high H2-evolution rate of 2258 μmol h−1 g−1 under a 300 W Xe lamp irradiation, which is about 2 times that of ZnS alone. The synergistic effect of cocatalysts contribute to the high performance of the hybrid photocatalyst, where graphene serves as an excellent electron acceptor and transporter, and MoS2 nanosheets provide a source of active reactive sites. It demonstrates that the exfoliated MoS2 nanosheets, achieved by the liquid exfoliation from natural molybdenite, can be used as an efficient cocatalyst to prepare high-performance photocatalysts in hydrogen evolution from water splitting.

Enhancement of photocatalytic H2 evolution over nitrogen-deficient graphitic carbon nitride

Nitrogen-deficient graphitic carbon nitride (g-C3N4−x) was synthesized by a hydrothermal treatment using ammonium thiosulfate as an oxidant. The as-prepared photocatalyst was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen adsorption–desorption, Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), elemental analysis (EA), electron paramagnetic resonance (EPR), UV-vis diffuse reflectance spectroscopy (UV-vis DRS) and photoluminescence (PL) spectroscopy. The visible-light-driven photocurrent measurement was performed by several on–off cycles of intermittent irradiation. The photocatalytic activity of catalysts was evaluated by splitting water under visible-light irradiation (λ > 420 nm). Results demonstrated that the photoactivity of g-C3N4−x was enhanced greatly by the deficiency of the terminal amino species on the catalysts. The average H2 evolution rate on g-C3N4−x was 31.6 μmol h−1, which was ca. 3 times higher than that on pristine g-C3N4. It was revealed that the unique nitrogen-deficient structure of g-C3N4−x played an important role in broadened visible-light absorption and efficient electron–hole separation, mainly accounting for the improved photocatalytic activity.

Fe-doped and ZnO-pillared titanates as visible-light-driven photocatalysts

Fe-doped cesium titanate was obtained by a solid state reaction with a mixture of Cs(2)CO(3), TiO(2), and Fe(2)O(3). ZnO-pillared doped titanate nanocomposite was successfully fabricated by exfoliating doped titanate and restacking its nanosheets with ZnO nanoparticles. The resulting nanocomposite was characterized by powder X-ray diffraction, scanning electron microscope, X-ray photoelectron spectroscopy, N(2) adsorption-desorption measurement, thermogravimetric analysis and UV-vis spectroscopy. It was revealed that the present nanocomposite exhibits greatly increased specific surface area with mesoporous texture and that there exists an electronic coupling between the host sheets and the guest nanoparticles in the pillared system. The results of degradation of methylene blue under visible light radiation suggest that doping iron ions improves the material spectral response region and that hybridizing with ZnO nanopillars can suppress the recombination of photogenerated electron-hole pairs.

Preparation and characterization of mesoporous SnO2-pillared HTaWO6 with enhanced photocatalytic activity

A porous SnO2-pillared HTaWO6 nanocomposite was assembled from tantalotungstate nanosheets and SnO2 nanoparticles via an exfoliation–restacking route and characterized by powder X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, UV-vis, X-ray photoelectron spectroscopy and N2 adsorption–desorption measurements. It was revealed that the obtained material has a gallery height of about 2 nm, a specific surface area of about 80 m2 g−1 and a wide pore size distribution with two extrema at about 2 and 3 nm. The mesoporous material exhibits enhanced photocatalytic activity in the degradation of MB, attributed to its high surface area, mesoporosity and the electronic coupling between the host and the guest components. A photoexcitation model of the semiconductor–semiconductor pillared photocatalyst was proposed based on the results of XPS and UV-vis.

Interstratified nanohybrid assembled by alternating cationic layered double hydroxide nanosheets and anionic layered titanate nanosheets with superior photocatalytic activity.

Oppositely charged 2D inorganic nanosheets of ZnAl-layered double hydroxide and layered titanate were successfully assembled into an interstratified nanohybrid through simply mixing the corresponding nanosheet suspensions. Powder X-ray diffraction and high-resolution transmission electron microscope clearly revealed that the component nanosheets in the as-obtained nanohybrid ZnAl-Ti3O7 retain the 2D sheet skeletons of the pristine materials and that the two kinds of nanosheets are well arranged in a layer-by-layer alternating fashion with a basal spacing of about 1.3 nm, coincident with the thickness summation of the two component nanosheets. The effective interfacial heterojunction between them and the high specific surface area resulted in that the nanohybrid exhibits a superior photocatalytic activity in the degradation of methylene blue with a reaction constant k of 2.81 × 10(-2)min(-1), which is about 9 and 4 times higher than its precursors H2Ti3O7 and ZnAl-LDH, respectively. Based on UV-vis, XPS and photoelectrochemical measurements, a proposed photoexcitation model was provided to understand its photocatalytic behavior.

Highly efficient photocatalytic hydrogen generation by incorporating CdS into ZnCr-layered double hydroxide interlayer

CdS-pillared ZnCr–LDH nanohybrid was prepared by incorporating CdS nanoparticles into the interlayer of ZnCr–LDH nanosheets via an exfoliation–restacking route. The resultant nanohybrid exhibits an interlayer spacing of 2.50 nm and a mesoporous texture with a specific surface area of 86 m2 g−1. It was revealed that there exists a strong electronic coupling between the two components in the pillared heterostructure, which remarkably suppresses the photogenerated electron–hole recombination. The as-prepared nanohybrid displayed significantly enhanced photocatalytic activity. Its H2-evolution rates were as high as 374 μmol h−1 g−1 with a quantum efficiency of 42.6% and 2164 μmol h−1 g−1 with a quantum efficiency of 48.2% under visible and UV-visible light, respectively, which were far superior to those of its parents ZnCr–LDH and CdS. The present findings clearly demonstrate that the self-assembly of CdS–LDHs is quite effective in synthesizing novel LDHs-based visible-light-driven photocatalysts with high performance in hydrogen evolution from water splitting.

Deprotonation of g-C3N4 with Na ions for efficient nonsacrificial water splitting under visible light

Developing a photocatalyst with the necessary characteristics of being cheap, efficient and robust for visible-light-driven water splitting remains a serious challenge within the photocatalysis field. Herein, an effective strategy, deprotonating g-C3N4 with Na ions from low-cost precursors, is reported. The deprotonated g-C3N4 exhibits a stable and reproducible H2 and O2 evolution rate of 31.5 and 15.2 μmol h−1 from pure water over 24 h. Our findings reveal that the extraordinary photoreactivity comes from the enhanced optical absorption, the promoted charge transfer, and the completely inhibited H2O2 intermediate due to the deprotonation.

Heterostructured Tin oxide-pillared tetratitanate with enhanced photocatalytic activity.

An effective active heterostructured photocatalyst of porous SnO(2)-pillared tetratitanate nanocomposite is synthesized by assembling tetratitanate nanosheets with SnO(2) nanoparticles via an exfoliation-restacking route. The nanocomposite was characterized by powder X-ray diffraction, high-resolution transmission electron microscope, thermogravimetric analysis, UV-vis DRS, X-ray photoelectron spectroscopy, and N(2) adsorption-desorption measurements. It was found that the pillared nanaocomposite is mesoporous with a gallery height of about 2 nm and a specific surface area of 154 m(2)/g. The pillared nanaocomposite exhibited enhanced photocatalytic activity in the photodegradation of Rhodamine B under UV light irradiation. The improved performance is attributed to the electronic coupling between the host and the guest components, as well as its high surface area and mesoporosity.

Preparation and electrical conductivity of polypyrrole/WS2 layered nanocomposites.

Lithium intercalated tungsten disulfide Li(x)WS(2) with x>1 was solvothermally obtained. It was revealed that Li(x)WS(2) can remain mostly unchanged under vacuum (about 4 kPa) for 5 days. The pH dependences of surface zeta potential for single molecular layers of WS(2) were determined, illustrating that its isoeletric point is approximately at pH 3. The polypyrrole/WS(2) layered nanocomposites were prepared via the combination of the exfoliation-restacking technique and in situ oxidative polymerization. The intercalation of PPy into the host galleries resulted in an interlayer expansion of about 3.7 A, which suggested that the intercalated polymeric chains are in a monolayer arrangement with the pyrrole rings lying parallel to the WS(2) host layers. The resulting material shows good thermal stability with the decomposition of the interacted chains within the disulfide galleries occurring at around 400 degrees C. The electrical conductivity of PPy/WS(2) nanocomposite was found to be high in the order of 10(-2) S cm(-1) at ambient temperature.

The synthesis, characterization and electrochemical performance of hollow sandwich microtubules composed of ultrathin Co3O4 nanosheets and porous carbon using a bio-template

Biomorphic 2D Co3O4 nanosheets/mesoporous carbon microtube composites are solvothermally prepared and subsequently calcined using ramie as a biotemplate. The as-prepared composites are fabricated using two sides of Co3O4 nanosheets (NSs) supported on porous carbon microtubes and exhibit a unique tubular morphology and porous features. The present biomorphic materials show a specific capacitance of 1280.6 F g−1 at 1 A g−1, and outstanding charge–discharge cycle stability with a capacitance retention of 96.89% after 15 000 cycles. The remarkable pseudocapacitive performance and cyclability are attributed to the unique microstructure, the high specific surface area and the optimized hierarchical microstructure inherited from the biotemplate.