Huaxiang Lin

Monolayered Bi2WO6 nanosheets mimicking heterojunction interface with open surfaces for photocatalysis.

Two-dimensional-layered heterojunctions have attracted extensive interest recently due to their exciting behaviours in electronic/optoelectronic devices as well as solar energy conversion systems. However, layered heterojunction materials, especially those made by stacking different monolayers together by strong chemical bonds rather than by weak van der Waal interactions, are still challenging to fabricate. Here the monolayer Bi2WO6 with a sandwich substructure of [BiO]+–[WO4]2−–[BiO]+ is reported. This material may be characterized as a layered heterojunction with different monolayer oxides held together by chemical bonds. Coordinatively unsaturated Bi atoms are present as active sites on the surface. On irradiation, holes are generated directly on the active surface layer and electrons in the middle layer, which leads to the outstanding performances of the monolayer material in solar energy conversion. Our work provides a general bottom-up route for designing and preparing novel monolayer materials with ultrafast charge separation and active surface.

In situ IR study of surface hydroxyl species of dehydrated TiO2: towards understanding pivotal surface processes of TiO2 photocatalytic oxidation of toluene

The surface species on P25-TiO(2) were characterized by FTIR after evacuation at 50-550 °C. The functions of OH groups on P25-TiO(2) catalysts have been tested by the adsorption and photooxidation of toluene in an in situ IR cell. FTIR studies show that the hydroxyl species on P25-TiO(2) are clearly temperature-dependent and P25-TiO(2) has six isolated hydroxyls with bands at 3734, 3715, 3688, 3671, 3658 and 3640 cm(-1). The OH groups on P25 play different roles in the photo-oxidation process: surface hydroxyls with bands at 3688, 3671, 3658 and 3640 cm(-1) act as adsorption sites while surface hydroxyls with bands at 3734 and 3715 cm(-1) act as sources of the ˙OH radical.

Photocatalytic and Antibacterial Properties of Medical-Grade PVC Material Coated With TiO2 Film

The TiO(2) film was coated on poly vinyl chloride (PVC) surface by dip-coating process from TiO(2)-PVC-THF suspension. The morphology and crystal structure of the as-synthesized samples were characterized by SEM and XRD. The photocatalytic properties were measured by the photodegradation reaction of RhB and the anti-adhesion and anti-bacteria for Escherichia coli. The results show that the resultant TiO(2) film is well-conglutinated on PVC surface and has the same crystal structure as the original TiO(2) powder. The TiO(2)/PVC shows excellent photocatalytic activity for the degradation of aqueous RhB and the activity increases with increasing reaction time and tends toward stable after accumulative illumination for 11.5 h. The TiO(2) film shows good bacterial anti-adhesion activity following photo-activation and sterilization property under UV irradiation. The E. coli can be killed completely after UV irradiation for 1.5 h.

Vacuum heat-treatment of carbon nitride for enhancing photocatalytic hydrogen evolution

Polymeric carbon nitride prepared by thermal condensation of cyanuric chloride with melamine was post-treated under vacuum conditions at different temperatures in order to study in depth the structure–performance relationship. The structure, composition, photoelectric and photocatalytic properties of the resulting samples were characterized in detail by physicochemical means, such as X-ray diffraction, thermogravimetry, elemental analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, photocurrent response, electrochemical impedance spectroscopy photocatalytic hydrogen production, etc. The results revealed that the untreated polymeric carbon nitride was not a single phase but a mixture consisting of unequal-sized particles with different degrees of polymerization and chemical structures containing both s-triazine and tri-s-triazine ring building blocks. This makes it possible to modify polymeric carbon nitride through a post-treatment. Tremendous changes in the C/N ratio, IR spectra, photoresponse, morphology, and photocatalytic activity occurred mainly in two temperature ranges of 300–500 °C and 500–600 °C. Among all samples, the carbon nitride treated at 500 °C showed the highest photocatalytic activity for production of hydrogen from water, as a result of the higher content of the tri-s-triazine phase, better lamellar morphology, wider photoabsorption, and smaller electrochemical impedance. The vacuum heat-treatment at temperature above 500 °C gave rise to the broken structure, and consequently the photoactivity was reduced.

Layered metal–organic framework/graphene nanoarchitectures for organic photosynthesis under visible light

A layered nanoarchitecture composed of photoactive MOFs of UiO-66-NH2 and graphene was facilely fabricated herein by an innovative strategy, which utilizes a noncovalent methodology for graphene functionalization combined with in situ self-assembling and a solvothermal synthesis technique. The fabricated hybrids were characterized and evaluated in detail by the selective photocatalytic oxidation of benzyl alcohol under visible light. The hybrid displayed improved efficiency with high selectivity, compared with the parent MOF. The characterization results clearly demonstrate that this originates from the sandwich-like hierarchical nanoarchitecture formed by the compact interaction between UiO-66-NH2 and graphene via the adopted mediator. The synthesis strategy was also proven effective in building the rGO/NH2-MIL-125(Ti) hierarchical nanoarchitecture. Thus, this work offers a general strategy for constructing MOF/graphene sandwich heterostructures, which have great potential in the fields of electronics, optics, optoelectronics, and photoconversion.

Robust Photocatalytic H2O2 Production by Octahedral Cd3(C3N3S3)2 Coordination Polymer under Visible Light.

Herein, we reported a octahedral Cd3(C3N3S3)2 coordination polymer as a new noble metal-free photocatalyst for robust photocatalytic H2O2 production from methanol/water solution. The coordination polymer can give an unprecedented H2O2 yield of ca. 110.0 mmol • L−1 • g−1 at pH = 2.8 under visible light illumination. The characterization results clearly revealed that the photocatalytic H2O2 production proceeds by a pathway of two-electron reduction of O2 on the catalyst surface. This work showed the potential perspective of Mx(C3N3S3)y (M = transitional metals) coordination polymers as a series of new materials for solar energy storage and conversion.

Controlled preparation of In2O3, InOOH and In(OH)3via a one-pot aqueous solvothermal route

Pure cubic In2O3, orthorhombic InOOH and cubic In(OH)3 nanocrystals were separately synthesized via a one-pot aqueous solvothermal route at low temperature by simply regulating the amount of water in the ternary system H2O–DMF–In(NO3)3·4.5H2O.

Visible light-driven decomposition of gaseous benzene on robust Sn2+-doped anatase TiO2 nanoparticles

This work shows the efficient degradation of benzene over robust Sn2+-doped TiO2 nanoparticles prepared by a facile sol–gel route under visible light irradiation. The structure, optical properties and chemical states of Sn species incorporated into anatase TiO2 were carefully characterized by X-ray diffraction, transmission electron microscopy, Raman, UV-vis diffuse reflectance, X-ray photoelectron, X-ray absorption, and electron spin resonance (ESR) spectroscopy. The maximal conversion rate of benzene achieved is up to 27% over the Sn/TiO2 with a Ti/Sn atomic ratio of 40 : 1 and remains constant for a cyclic run of six days, indicating the high photo-stability for the decomposition of benzene. The characterization results reveal that the Sn2+-doping narrows the band gap energy of anatase TiO2, leading to a visible-light response. The photocatalytic degradation pathway of benzene was proposed based on the results of ESR and Fourier transform infrared spectra. These results offer a full comprehension of the visible light photocatalysis of Sn2+-doped TiO2 for degradation of volatile organic pollutants.

A novel Zn2GeO4 superstructure for effective photocatalytic hydrogen generation

Crystal orientation-ordered hexagonal Zn2GeO4 nanorod-bundles have been obtained via a synergistic self-assembly route. Each nanorod unit of the bundles maintains its individual hexagonal rod-shaped structure and is dominated by (110) and (0) facets, and all of them are aligned parallel to the growth direction in a high density. An ordered self-assembly of anisotropic nanorods was suggested to elucidate the formation of the unique bundle structures. The novel structure of Zn2GeO4 bundles assembled from hexagonal nanorods leads to a surprisingly high UV-light-driven activity for the photocatalytic decomposition of water–methanol solution to hydrogen. The correlation of structure and photocatalytic activity of the ordered nanorod-bundles was discussed, indicating a new strategy of bundling Zn2GeO4 nanorods with reactive facets to effectively enhance photocatalytic activities of 1-D nanostructures.

Large-scale preparation of heterometallic chalcogenide MnSb2S4 monolayer nanosheets with a high visible-light photocatalytic activity for H2 evolution

Free standing MnSb2S4 2D monolayer nanosheets were developed by a simple calcination of the neutral hydrazine molecule bridged chalcogenide, and were found to display a highly efficient and stable activity for photocatalytic hydrogen evolution from water under visible light irradiation (420-730 nm).