Search

Engineering lattice defects in two-dimensional (2D) sulfide semiconductors has been accepted as an effective strategy to enhance the efficiency of the solar-to-fuels conversion. Although many researches have proven the lattice defect-mediated photocatalytic activity of ZnIn2S4, the artificial control of S-defects for optimizing the charge-carrier kinetics process in ZnIn2S4 has long been a challenging task. Herein, we report a facile one-step method to modulate the lattice S-content of ZnIn2S4 microflowers (MFs) only through adjusting the used amount of S-precursor in the hydrothermal solution that contains the metal precursors with a fixed Zn/In stoichiometric ratio at 1:2. We also demonstrated that the S-vacancies at the In facets were the main type of lattice defects in the formed ZnIn2S4 MFs, which could enhance both the separation and migration processes of the photoinduced charge-carriers due to the existence of discrete defect energy-levels (DELs) and the reduced effective mass of electrons, as evidenced by the first-principles calculations and the electron spectra analyses. The ZnIn2S4 MFs with the optimal content of S-vacancy obtained by a hydrothermal treatment of the precursors with the Zn/In/S stoichiometric ratio of 1:2:8 possessed the long-lived photoinduced electron (~94.64 ns) for contributing to the photo-physical and -chemical processes. Thus, upon visible light irradiation, the H2-evolution rate of this sample reached ~ 2.40 mmol h−1 g−1 with an apparent quantum efficiency of ~ 0.16% at 420 nm even though only using 5 mg of photocatalysts without any cocatalysts.

Metal–organic framework (MOF) materials have been extensively incorporated with inorganic semiconductor photocatalysts to improve their photocatalytic activity through an efficient charge transfer process across their heterointerface. In this work, octahedral UiO-66-NH2 MOFs with edge-lengths of 110–330 nm are uniformly decorated on the surface of TiO2 electrospun nanofibers by a traditional solvothermal method combined with activation pretreatment. Before the solvothermal growth of UiO-66-NH2, the TiO2 electrospun nanofibers were activated in NaOH solution to etch the TiO2 surface for allowing the exposure of lattice oxygen. The exposed lattice oxygen on the TiO2 surface could interact with the MOF precursor of Zr4+ ions, thus enabling octahedral UiO-66-NH2 to grow uniformly on the surface of TiO2 nanofibers with an intimate Ti–O–Zr hetero-interface. Such an intimate hetero-interface provides an effective channel for boosting the electron transfer between UiO-66-NH2 and TiO2 in their heterostructure. Thus, the UiO-66-NH2/TiO2(anatase) heterostructures exhibited enhanced photocatalytic activity for H2 production as compared to either TiO2(anatase) nanofibers or UiO-66-NH2 nanooctahedra in the presence of Rhodamine B (RhB) as a sensitizer under visible light irradiation. In particular, the decoration of UiO-66-NH2 nanooctahedra on anatase/rutile mixed TiO2 nanofibers could induce further enhancement of the photocatalytic H2 production. The enhanced photocatalytic activity is attributed to the multi-step continuous interfacial transfer of photoinduced electrons with the way of RhB → UiO-66-NH2 → TiO2(anatase) → TiO2(rutile).

Mo-doped BiVO4 microcrystals with tetragonal structures were prepared by a hydrothermal method. The phase transformation from monoclinic to tetragonal was observed as the concentration of molybdenum ions increased up to 10 mol%. Accordingly, the morphology of the as-preparation samples evolved from plate-shaped (molybdenum-free BiVO4) to pie-like (BiVO4:Mo). The photocatalytic activity of BiVO4:Mo with a tetragonal structure was much higher than that of the pure BiVO4 host with a monoclinic phase by using RhB as the simulated pollutants under sun-like irradiation. The degradation rate of RhB was increased from 40% with molybdenum-free BiVO4 to 97.8% with the Mo-doped BiVO4 materials.

Engineering semiconductor-based homo- (hetero-) junctions in hierarchical nanostructures is a promising way to achieve the high performance and recyclable photocatalysts toward pollutants degradation in water. Herein, we develop a kind of hierarchical p–n heterojunctions photocatalysts through controllable decoration of ultrathin p-BiOBr nanosheets onto n-TiO2 electrospun nanofibers by using a traditional solvothermal method. Structural characterization results indicate that the BiOBr nanosheets are assembled uniformly onto the TiO2 nanofibers. This well-designed hierarchical p–n heterojunctions in the p-BiOBr/n-TiO2 nanofibers photocatalyst lead to not only the improved generation/separation of photoinduced charges-carriers, but also the increased amount of redox sites. Benefiting to these advantages, the optimal p-BiOBr/n-TiO2 nanofibers exhibited the apparent rate constant of 0.1 and 0.15 min−1 for photocatalytic RhB and MO degradation under UV-light irradiation, which is twice and three times higher than that of mechanically mixtured BiOBr nanosheets and TiO2 nanofibers, respectively. Control experiments demonstrate that both the photoinduced electrons and the oxygen free radicals play the major roles on the enhancement of photocatalytic activity. Moreover, the p-BiOBr/n-TiO2 nanofibers photocatalysts with the unique nonwoven structure can be easily recycled without secondary pollution, in particular, still maintaining almost the initial photocatalytic activity during the wastewater treatment.

Herein, an interesting electron-donating strategy is proposed to guide the construction of novel CdS-based MOFs for co-catalyst-free photocatalytic H2 evolution in the presence of triethanolamine as the hole-scavenger. The optimally designed CdS-based MOF exhibits an exceptional H2-evolution rate of 26.1 mmol g−1 h−1 which is almost the highest rate among the reported co-catalyst-free MOF systems.

The NaYF4:Yb,Er/W18O49 heterostructure is an excellent photocatalyst that can promote H2 evolution by hydrolyzing BH3NH3 under near-infrared (NIR) light irradiation. At the same time, the photothermal effect can be produced in photocatalytic reactions, which will cause the luminescence efficiency and photocatalytic activity to decrease. Determining how to take advantage of that photothermal effect becomes a major problem. Moreover, the energy transfer (ET) process from Er ions to Nd ions in NaYF4 co-doped with Yb/Er/Nd ions (NaYF4:Yb,Er,Nd) occurred at high temperature. Herein, the NaYF4:Yb,Er,Nd/W18O49 quasi-core–shell heterostructure was designed to achieve better H2 production capacity; this heterostructure exhibits a 1.5-fold enhancement of photocatalytic activity for H2 evolution as compared with the NaYF4:Yb,Er/W18O49 heterostructure. This study provides a new way to explore the catalytic activities in the NIR field for application in the development of a sustainable energy source.

In this work, the lacunary Keggin-type phosphotungstates of [PW9O34]9- (PW9) clusters were loaded onto the g-C3N4 nanosheets (NSs) to synthesize the phosphotungstate clusters-decorated 2D heterojunction photocatalysts by using the electrostatic-force driven self-assembly process. The surface charge polarity of g-C3N4 NSs was changed from a negative to a positive charge through the acidizing treatment. The positively-charged g-C3N4 NSs allowed the negatively-charged PW9 clusters to be adsorbed and deposited onto the g-C3N4 NSs, forming the PW9/g-C3N4 heterojunction NSs. The as-synthesized samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, and UV-VIS absorption spectra, respectively. The photocatalytic activity tests indicated that, upon simulated sunlight irradiation, the photocatalytic H2-generation rate of PW9/g-C3N4 heterojunction NSs (~23.8 &mu, mol h&minus, 1) was ~3.3 times higher than that of the pure g-C3N4 NSs (~7.3 &mu, 1). The enhanced photocatalytic activity of PW9 cluster-decorated g-C3N4 NSs could be attributed to the enhanced separation process of the photoinduced charge-carriers, due to the Z-scheme-mediate charge transfer behavior across their hetero-interface.

Engineering the multi-hetero-junctions in semiconductor photocatalysts has been recognized as a promising way to achieve highly efficient photocatalytic solar-fuel generation, because the photoinduced heterointerfacial charge transfer can greatly hinder the recombination process of charge-carrier in photocatalysts. In this work, we fabricated copper species nanocrystals/TiO2 multi-hetero-junction photocatalysts through in situ reduction of CuO nanocrystals in CuO/TiO2 electrospun nanofibers by a hydrothermal method assisted by glucose. By changing the concentration of glucose, the composition ratio of copper species nanocrystals, including CuO, Cu2O, and Cu, can be adjusted in multi-hetero-junction nanofibers. Upon simulated sunlight irradiation, the optimal copper species nanocrystals/TiO2 multi-hetero-junction nanofibers exhibited an H2 evolution rate of ∼10.04 μmol h–1, a 17.3 times increase over that of bare TiO2 nanofibers (∼0.57 μmol h–1).

An enhancement of the photocatalytic activity of Titanium dioxide nanosheets (TiO2 NFs) by N2 plasma (N-plasma) treatment has been suggested. TiO2 NFs was synthesized by a solvothermal method and treated with N-plasma at atmospheric pressure. Then the as-prepared TiO2 and N-plasma treated TiO2 (N-TiO2) NFs photocatalyst were extensively characterized. Interestingly, more oxygen vacancy and Ti3+ ions were found in the N-TiO2 NFs. Meanwhile, Ti3+ ions form the Ti3+ self-doped system, which causing the light absorption range enhanced. The catalytic H2 evolution of N-TiO2 NFs at a rate of 8.1 mmol g−1 h−1, which is 14.85 times higher than that of the pristine TiO2 NFs. These results might suggest new views for the photoactivity of TiO2 NFs and provide a kind of feasibility for other metal oxides in the photocatalytic field.

In this letter, we developed a self-cleaning coating material through simply blending the TiO2 porous microspheres (PMS) with the commercial cement. The TiO2 PMS with the diameters around 500 nm were synthesized by an ultrasonic spray pyrolysis method. During the photocatalytic depollution tests, the as-prepared TiO2 PMS/cement composite was processed into a hardened micro-film coated on the glass substrate via a doctor blade method. Upon UV–Vis light irradiation, the TiO2 PMS/cement composite film exhibited the higher photocatalytic activity as compared to the conventional P25/cement composite film. This can be attributed to the fact that the unique micro-nano hierarchical porous structure of TiO2 PMS not only boosts the light harvesting ability, but also provides more active sites for the photocatalytic reaction.

Rational arrangement of nanosized semiconductor components in the multi-heterojunction photocatalyst can lead to the formation of a high-speed transport channel for charge-carriers separation and migration, which provides a promising way to achieve excellent photocatalytic efficiency for solar fuels generation. Herein, we develop a photo-assisted self-optimization strategy to re-build the charge-carriers transport channel in the copper species nanocrystals/TiO2 electrospun nanofibers with the organic hydrogen-carrier molecules as the photo-reactants. As a result of the dynamics difference of the excitons migration during the photocatalytic process, the binary CuO/TiO2 heterojunction nanofibers are recrystallized to form the quaternary Cu/Cu2O/CuO/TiO2 multi-heterojunction nanofibers that exhibits a higher rate constant ( ∼ 1.7 × 10 8 S − 1 ) for the interfacial electron-transfer than the former nanofibers ( ∼ 0.7 × 10 8 S − 1 ) due to the improved charge-carriers transport channel. In this way, a 40-fold enhanced H2 generation rate was observed on the recrystallized nanofibers photocatalyst during the photocatalytic decomposition of formic acid as compared to the pure TiO2 nanofibers. Our work presents an available paradigm to skillfully use a transient photo-physicochemical process to mildly engineer a high-quality charge-carriers transport channel in the hetero-nanophotocatalyst for realizing an optimal photocatalytic performance.

Macrostructural flexible photocatalysts have been proven to have desirable recyclable properties during the photocatalytic degradation of organic pollutants in water. However, the photocatalytic activities of these photocatalysts are often unsatisfactory due to the fast recombination of charge carriers and the limited surface active sites. Herein, we developed a novel flexible photocatalyst of AgBr/BiOBr/polyacrylonitrile (PAN) composite mats (CMs) through the controllable assembly of AgBr/BiOBr nano-heterostructures on electrospun polyacrylonitrile nanofibers (PAN NFs) via a three-step synthesis route. The component ratio of AgBr to BiOBr in the CMs could be easily adjusted by controlling the in situ ion exchange process. The charge&ndash, transfer process occurring at the interface of the AgBr/BiOBr nano-heterostructures strongly hindered the recombination of photoinduced electron&ndash, hole pairs, thereby effectively enhancing the photocatalytic activity of the AgBr/BiOBr/PAN CMs. Meanwhile, the unique hierarchical inorganic/organic heterostructure of the AgBr/BiOBr/PAN CMs not only led to good flexibility, but also provided an abundance of active sites for photocatalytic reactions. Upon visible-light irradiation, AgBr/BiOBr/PAN CMs with an optimal ratio of AgBr to BiOBr components exhibited both enhanced photocatalytic activity and excellent separability during the degradation of methyl orange in water compared to the BiOBr/PAN CMs.

The hetero-interface quality and area in the semiconductor heterostructure are important to the photocatalytic performance of the heterostructure. The 2D hetero-interface between two 2D semiconductors has been widely proved to enhance the photocatalytic performance, because the larger contact area of the hetero-interface can effectively improve the charge separation behavior. However, engineering high-quality 2D multi-hetero-interface in the well-designed semiconductor composite to further enhance the charge separation and utilization is still a big challenge. Herein, we constructed the 2D multi-hetero-interface in the well-designed nanosheet (NS) composite photocatalyst through an in-situ oxidation treatment combined with the electrostatic self-assembly strategy. The negatively-charged binary Ti3C2Tx/(001)TiO2 heterojunction NSs with the intimate 2D contact interface was fabricated through a facile in-situ oxidation method, while the protonated g-C3N4 NSs were positively charged. Thus, the spontaneous electrostatic attraction behavior between the above opposite-charged materials of the Ti3C2Tx/(001)TiO2 heterojunction and the g-C3N4 NSs enables the 2D multi-hetero-interface to be constructed in the Ti3C2Tx/(001)TiO2/C3N4 NSs. As such, the 2D multi-hetero-interface offers broad electron-transfer channels to enhance the charge separation and utilization. Upon simulated sunlight irradiation, the optimal Ti3C2Tx/(001)TiO2/C3N4 NSs achieved about 4-fold enhancement on the photocatalytic H2 generation and 3-fold improvement on the photocatalytic CO2 reduction as compared to the pure (001)TiO2 or g-C3N4 NSs.

Rational assembly of small-sized photosensitizers onto 2D semiconductors can effectively promote the photocatalytic activity of the formed 2D heterojunction photocatalyst due to the hetero-interfacial charge-transfer process. However, the achievement of the 2D semiconductor-based heterojunction photocatalyst with the exposures of both abundant light-harvesting and catalytic sites at the hetero-interface region is still a huge challenge. Herein, we synthesized phosphotungstic acid/graphitic carbon nitride (HPW/g-C3N4) heterojunction nanosheets (NSs) with the highly-dispersed distribution of ultra-small HPW clusters (1∼2 nm) by using a facile self-assembly method based on the static adsorption-deposition process. The formed molecular-scale hetero-interface between HPW clusters and g-C3N4 NSs resulted in the exposure of abundant active-sites on the highly-dispersed HPW/g-C3N4 hetero-interface. By combining the steady-state and transient photoluminescence spectra with the wavelength-controlled experiments, we demonstrated that the hetero-interfacial charge-transfer process occurring in the HPW/g-C3N4 heterojunction NSs obeyed the Z-scheme mechanism rather than the common “type-II” heterojunction mechanism. In this way, the lifetimes of photoinduced electrons on the conduction band of g-C3N4 could be prolonged for initiating the photocatalytic solar-to-fuels conversion. Upon interband excitations of both the two hetero-components in the HPW/g-C3N4 heterojunction NSs, the photocatalytic activities of H2 generation and CO2 reduction could be enhanced by ∼2.2 and ∼6.7 times as compared to the pure g-C3N4 NSs, even though the HPW component was photocatalytic-inert for either H2 generation or CO2 reduction upon UV–vis light irradiation.

Atmospheric Particulate matter (PM) with small sizes has caused a serious air-pollution problem calling for high-performance PM-capture materials and promising remediation strategies. In this contribution, we propose a new idea to proactively capture PM and simultaneously in-situ convert the captured PM pollution over the flexible schottky-junctions nanofiber membrane (NFM) consisting of rutile TiO2 nanoparticles (NPs)-decorated electrospun carbon NFs. We also demonstrate that both the interfacial electron-transfer process at the TiO2/carbon schottky-junctions and the photo-excitation process at the surface of TiO2 NPs can induce polarization fields in the TiO2/carbon NFM due to the difference of the space-charge distribution. These multilevel polarization fields can drive the long-range electrostatic force to enhance the proactive PM-capture ability of the NFM. As such, the TiO2/carbon NFM exhibited a satisfactory quality factor (0.11 Pa−1) for balancing the PM2.5-filtration efficiency (99.92 %) and the pressure drop (only 63 Pa). More importantly, upon UV–vis-light irradiation, 92.98 % of the ultrafine PM0.3 was removed over this TiO2/carbon NFM. Furthermore, the as-captured PM on the NFM could be photocatalytically decomposed by the photoactive-component of TiO2 NPs, during which some of the carbonaceous PM was converted into the fuels of such CO and CH4 through a multi-step photoreaction.

The charge-carrier dynamics process in well-designed hetero-nanostructural plasmonic photocatalysts is greatly improved through a multichannel sensitization effect, which therefore results in a significant enhancement of the efficiencies of solar-to-fuels conversion.

In this work, we present the 2D/2D type of heterojunction photocatalysts fabricated by horizontal loading ultrathin hexagonal SnS2 nanosheets on g-C3N4 nanosheets through a facile ultrasonic dispersion method. The sheet-like structures of these two nanomaterials induce a large contact region in the heterojunction interface, as evidenced by electron microscopic analyses. By taking advantage of this feature, the as-fabricated SnS2/g-C3N4 heterojunction nanosheets exhibit considerable improvement on the photocatalytic activities for the degradation of organic dyes and phenols under visible light irradiation as compared to pure g-C3N4 and SnS2 nanosheets. In particular, the optimal heterojunction nanosheet with 5.0 wt.% SnS2 shows the apparent rate constant of ∼0.2 min−1 for the RhB photodegradation, which is higher than that of pure g-C3N4 and SnS2 nanosheets by a factor of 4 and 8, respectively. Further studies by steady-state and transient photoluminescence spectroscopy indicate that the photosynergistic effect of SnS2/g-C3N4 heterojunction can remarkably enhance the photoinduced interfacial charge transfer, thereby increasing the charge separation during the photocatalytic reaction.

Up-conversion luminescence (UCL) from rare-earth doped oxide (RE) films has great potential for application in fields such as solar cells, bioanalysis, or display technologies. However, the relatively high phonon energy of oxide matrices usually facilitates nonradiative relaxation leading to low UCL efficiency. Herein, we report a three-layer hierarchical structure of Ag/ZnO nanowires (nw-ZnO)/RE composite films, which enhances the UCL of rare-earth doped oxide films. An optimization of the geometric structure of the composite films demonstrated an increase of UCL by up to almost two orders of magnitude in Er3+ and Tm3+ doped YbMoO4 films. This UCL enhancement is attributed to the formation of a very strong electric field in the tips of the nw-ZnO creating a highly effective electric field at the composite films, combined with reflection at the silver layer. Furthermore, we use the UCL properties of these novel Ag/nw-ZnO/RE composite films to demonstrate their possible use in ZnO-based photocatalytic processes to enhance the utilization of near-infrared sunlight in these devices.

One-dimensional (1D) Pt/TiO2 hybrid nanofibers (HNFs) with different concentrations of Pt were fabricated by a facile two-step synthesis route combining an electrospinning technique and calcination process. X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM) results showed that the Pt nanoparticles (NPs) with the size of 5–10 nm were well dispersed in the TiO2 nanofibers (NFs). Further investigations from the UV–Vis diffuse reflectance (DR) and X-ray photoelectron spectroscopy (XPS) analysis revealed that some Pt ions were incorporated into the TiO2 lattice as Pt4+ state, which contributed to the visible light absorption of TiO2 NFs. Meanwhile, the Pt2+ ions existing on the surface of Pt NPs resulted in the formation of Pt–O–Ti bond at Pt NPs/TiO2 NFs interfaces that might serve as an effective channel for improving the charge transfer. The as-electrospun Pt/TiO2 HNFs exhibited remarkable activities for photocatalytic H2 evolution under visible light irradiation in the presence of l -ascorbic acid as the sacrificial agent. In particular, the optimal HNFs containing 1.0 at% Pt showed the H2 evolution rate of 2.91 μmol h−1 and apparent quantum efficiency of 0.04% at 420 nm by using only 5 mg of photocatalysts. The higher photocatalytic activity could be ascribed to the appropriate amount of Pt ions doping and excellent electron-sink effect of Pt NPs co-catalysts.

Direct evidence of plasmon-enhanced H2 generation is observed in photocatalytic water reduction by using TiO2 electrospun nanofibers co-decorated with Au and Pt nanoparticles through dual-beam irradiation. The Au/Pt/TiO2 nanofibers exhibit certain activity for H2 generation under single irradiation at 420 nm that excites the defect/impurity states of TiO2. Significantly, when secondary irradiation at 550 nm is introduced to simultaneously excite Au SPR, we observed 2.5 times higher activity for H2 generation. Further investigation by finely controlling the irradiation wavelengths reveals that the enhancement factor on the photocatalytic activity for H2 generation is directly correlated with the plasmon absorption band of the Au nanoparticles in the Au/Pt/TiO2 nanofibers. The control experiments with different sacrificial agents suggest that the hot plasmonic electrons of Au are responsible for the enhanced photocatalytic activity that can be magnified when TiO2 is simultaneously excited. Accepted version

We present the fabrication of TiO2 nanofibers codecorated with Au and Pt nanoparticles through facile electrospinning. The Au and Pt nanoparticles with sizes of 5–12 nm are well-dispersed in the TiO2 nanofibers as evidenced by electron microscopic analyses. The present design of Au/Pt codecoration in the TiO2 nanofibers leads to remarkably enhanced photocatalytic activities on both hydrogen generation and CO2 reduction. This great enhancement is attributed to the synergy of electron-sink function of Pt and surface plasmon resonance (SPR) of Au nanoparticles, which significantly improves charge separation of photoexcited TiO2. Our studies demonstrate that through rational design of composite nanostructures one can harvest visible light through the SPR effect to enhance the photocatalytic activities of semiconductors initiated by UV-light to more effectively utilize the whole solar spectrum for energy conversion.

We report a new type of Au@TiO2-CdS ternary nanostructures by decorating CdS nanoparticles onto Au@TiO2 core-shell structures. Comparing to the binary structures, such as CdS-TiO2 and Au@TiO2, these ternary nanostructures exhibit remarkably high photocatalytic H2 generation rate under visible-light irradiation. The enhanced photocatalytic activity is attributed to the unique ternary design, which builds up a transfer path for the photoexcited electrons of CdS to the core Au particles via the TiO2 nanocrystal bridge, and thus effectively suppressed the electron-hole recombination on the CdS photocatalyst. This internal electron transfer pathway (CdS→TiO2→Au) eliminates the needs of post-deposition of metal co-catalyst since the core Au nanoparticle can act as the interior active catalyst for proton reduction towards hydrogen evolution. We believe that our work demonstrates a promising way for rational design of metal-semiconductor hybrid photocatalysts to achieve high photocatalytic efficiency for solar fuels production. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore) Accepted version

Ultrabroad-spectrum absorption and highly efficient generation of available charge carriers are two essential requirements for promising semiconductor-based photocatalysts, towards achieving the ultimate goal of solar-to-fuel conversion. Here, a fascinating nonmetal plasmonic Z-scheme photocatalyst with the W18 O49 /g-C3 N4 heterostructure is reported, which can effectively harvest photon energies spanning from the UV to the nearinfrared region and simultaneously possesses improved charge-carrier dynamics to boost the generation of long-lived active electrons for the photocatalytic reduction of protons into H2 . By combining with theoretical simulations, a unique synergistic photocatalysis effect between the semiconductive Z-scheme charge-carrier separation and metal-like localized-surface-plasmon-resonance-induced "hot electrons" injection process is demonstrated within this binary heterostructure.

Ternary heterostructured nanofibers (NFs) consisting of plasmonic noble metal nanoparticles (Au, Ag, or Pt NPs), graphitic carbon nitride nanosheets (g-C3N4 NSs), and TiO2 NPs were synthesized in situ via a facile electrospinning technique combined with a subsequent thermal oxidation/reduction process. The thermal-reduced plasmonic NPs with sizes from 5 to 10 nm are dispersed uniformly into the heterojunctions of the NFs that are formed by thermal oxidation etching of exfoliated g-C3N4 NSs in the electrospun TiO2 nanofibrous matrix, as evidenced by microscopic and electronic structure analyses. In comparison to single-component photocatalysts, such as g-C3N4 NSs or TiO2 NFs, these ternary heterostructures exhibit significantly high photocatalytic activity for H2 evolution under simulated sunlight irradiation. The enhanced photoactivities are attributed to the strong photosynergistic effect between the surface plasmon resonance (SPR) and the heterojunction interface sensitization, which results in the improvement of charge-carrier generation and separation in the ternary heterostructured NFs. Further investigations indicate that coupling heterojunction sensitization on the g-C3N4/TiO2 interface with Ag SPR effects by plasmonic resonant energy transfer is the optimal strategy for synergistically improving the charge-carrier kinetics to achieve highly efficient photocatalytic H2 evolution. It is believed that our present study offers a promising method for the rational integration of multi-component photocatalytic systems that can realize high photocatalytic performances for use in solar-to-fuel conversion.

We have realized in-situ growth of ultrathin ZnIn2S4 nanosheets on the sheet-like g-C3N4 surfaces to construct a “sheet-on-sheet” hierarchical heterostructure. The as-synthesized ZnIn2S4/g-C3N4 heterojunction nanosheets exhibit remarkably enhancement on the photocatalytic activity for H2 production. This enhanced photoactivity is mainly attributed to the efficient interfacial transfer of photoinduced electrons and holes from g-C3N4 to ZnIn2S4 nanosheets, resulting in the decreased charge recombination on g-C3N4 nanosheets and the increased amount of photoinduced charge carriers in ZnIn2S4 nanosheets. Meanwhile, the increased surface-active-sites and extended light absorption of g-C3N4 nanosheets after the decoration of ZnIn2S4 nanosheets may also play a certain role for the enhancement of photocatalytic activity. Further investigations by the surface photovoltage spectroscopy and transient photoluminescence spectroscopy demonstrate that ZnIn2S4/g-C3N4 heterojunction nanosheets considerable boost the charge transfer efficiency, therefore improve the probability of photoinduced charge carriers to reach the photocatalysts surfaces for highly efficient H2 production.

The 3D open Bi(2)MoO(6)/ZnTiO(3) hierarchical heterostructures with Bi(2)MoO(6) ultrathin nanosheets (

The ZnO quantum dots-SiO(2) nanotubes (ZQDs-SNTs) nanocomposite was successfully fabricated by direct heat treatment of the electrospun zinc acetate/tetraethyl orthosilicate (TEOS)/polymer nanotubes (NTs). The results indicated that the ZnO quantum dots (ZQDs) with diameter about 3-5 nm were highly dispersed on the SiO(2) nanotubes (SNTs). And, there might be Zn-O-Si bonds between ZQDs and SiO(2) matrix, which formed interface states in the ZQDs-SNTs nanocomposite. The photocatalytic studies revealed that the ZQDs-SNTs nanocomposite exhibited high photocatalytic activity to degrade Rhodamine B (RB) under ultraviolet (UV) light irradiation, which might be ascribed to two reasons. The first one was the high dispersity of ZQDs; another one was the high separation efficiency of photogenerated electron-hole pairs due to the trap effect for photogenerated electrons of the interface states between ZQDs and SiO(2). During the photocatalytic reaction, the ZQDs-SNTs nanocomposite also exhibited high chemical stability in a wide range of pH values, which might be ascribed to the protective action of SiO(2) and the presence of Zn-O-Si bonds between ZQDs and SiO(2). Furthermore, the ZQDs-SNTs nanocomposites could be easily recycled because of their one-dimensional nanostructure property.

One-dimensional Bi2MoO6/TiO2 hierarchical heterostructures with different secondary Bi2MoO6 nanostructures grown on primary TiO2 nanofibers have been obtained by a combination of electrospinning and a solvothermal technique. The morphology of the secondary Bi2MoO6 nanostructures could be controlled by adjusting the precursor concentration, and then two different morphologies of Bi2MoO6/TiO2 heterostructures with Bi2MoO6 nanoparticles and nanosheets were successfully achieved. Photocatalytic tests displayed that the Bi2MoO6/TiO2 heterostructures possessed a much higher degradation rate of Rhodamine B (RB) than the unmodified TiO2 nanofibers and Bi2MoO6 under UV and visible light. The enhanced photocatalytic activity could be attributed to the extended absorption in the visible light region resulting from the Bi2MoO6 nanosheets, and the effective separation of photogenerated carriers driven by the photoinduced potential difference generated at the Bi2MoO6/TiO2 heterojunction interface. Moreover, the heterostructures could be reclaimed easily by sedimentation without a decrease of the photocatalytic activity.

One-dimensional In2O3 nanocubes/carbon nanofibers (CNFs) heterostructures have been successfully obtained by a simple combination of electrospinning technique and solvothermal process for the first time. The as-obtained products were characterized by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and IR spectra. The results revealed that the secondary In2O3 nanocubes were successfully grown on the primary CNF substrates. Photocatalytic tests displayed that the In2O3/CNFs heterostructures possessed a much higher degradation rate of rhodamine B (RB) than the pure In2O3 under visible light. The enhanced photocatalytic activity could be attributed to the formation of heterostructures, which might improve the separation of photogenerated electrons and holes. Moreover, the In2O3/CNF heterostructures could be easily recycled without the decrease of the photocatalytic activity due to their one-dimensional nanostructural property. The morphology of the secondary In2O3 nanostructures (nanocubes, nanoagglomerates or nanoparticles) could be controlled by adjusting the additives including CO(NH2)2 and a defined amount of water. The general growth mechanisms for the In2O3 nanostructures have also been discussed.

In this paper, a facile two-step synthesis route combining an electrospinning technique and solvothermal method has been presented as a straightforward protocol for the exploitation of Bi2MoO6–carbon nanofiber (CNF) hierarchical heterostructures, which are composed of Bi2MoO6 nanosheets on the surface of CNFs. Photocatalytic tests show that the Bi2MoO6–CNF heterostructures possess a much higher degradation rate of Rhodamine B (RB) than pure Bi2MoO6 under visible light. The enhanced photocatalytic activity may be attributed to the extended absorption in the visible light region due to the Bi2MoO6 nanosheets, and the effective separation of the photogenerated carriers driven by the photoinduced potential difference produced at the Bi2MoO6–CNF heterojunction interface. Moreover, the heterostructures could be recovered easily by sedimentation without a decrease in their photocatalytic activity. The morphology of the secondary Bi2MoO6 nanostructures could be controlled by adjusting the experimental parameters, including the precursor concentration, temperature and solvent during the solvothermal process. As a result, different morphologies of Bi2MoO6–CNF heterostructures, with Bi2MoO6 nanosheets, nanoparticles, nanoflowers and nanorods, were successfully achieved.

One-dimensional In(2)O(3)-TiO(2) heteroarchitectures with high visible-light photocatalytic activity have been successfully obtained by a simple combination of electrospinning technique and solvothermal process. The as-obtained products were characterized by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV-vis spectra. The results revealed that the secondary In(2)O(3) nanostructures were successfully grown on the primary TiO(2) nanofibers substrates. Compared with the pure TiO(2) nanofibers, the obtained In(2)O(3)-TiO(2) heteroarchitectures showed enhancement of the visible-light photocatalytic activity to degrade rhodamine B (RB) because of the formation of heteroarchitectures, which might improve the separation of photogenerated electrons and holes derived from the coupling effect of TiO(2) and In(2)O(3) heteroarchitectures. Moreover, the In(2)O(3)-TiO(2) heteroarchitectures could be easily recycled without the decrease in the photocatalytic activity because of their one-dimensional nanostructural property.

A novel photocatalyst of nanostructured cadmium phthalocyanine (CdPc) immobilized on the surface of polyacrylonitrile (PAN) nanofibers had been successfully fabricated by a simple combination of electrospinning technique and the solvent-thermal process. FE-SEM micrographs indicated that the nanostructured CdPc uniformly immobilized on the surface of PAN nanofibers without agglomeration. And the obtained CdPc/PAN composite nanofibers exhibited high visible light photocatalytic activity for the degradation of rhodamine B. Moreover, this photocatalyst could be easily separated for reuse due to the one-dimensional nanostructural property of the CdPc/PAN composite nanofibers.

Plasmonic metal nanostructures have been widely used to enhance the upconversion efficiency of the near-infrared (NIR) photons into the visible region via the localized surface plasmon resonance (LSPR) effect. However, the direct utilization of low-cost nonmetallic semiconductors to both concentrate and transfer the NIR-plasmonic energy in the upconversion system remains a significant challenge. Here, a fascinating process of NIR-plasmonic energy upconversion in Yb3+/Er3+-doped NaYF4 nanoparticles (NaYF4:Yb-Er NPs)/W18O49 nanowires (NWs) heterostructures, which can selectively enhance the upconversion luminescence by two orders of magnitude, is demonstrated. Combined with theoretical calculations, it is proposed that the NIR-excited LSPR of W18O49 NWs is the primary reason for the enhanced upconversion luminescence of NaYF4:Yb-Er NPs. Meanwhile, this plasmon-enhanced upconversion luminescence can be partly absorbed by the W18O49 NWs to re-excite its higher energy LSPR, thus leading to the selective enhancement of upconversion luminescence for the NaYF4:Yb-Er/W18O49 heterostructures. More importantly, based on this process of plasmonic energy transfer, an NIR-driven catalyst of NaYF4:Yb-Er NPs@W18O49 NWs quasi-core/shell heterostructure, which exhibits a ≈35-fold increase in the catalytic H2 evolution from ammonia borane (BH3NH3) is designed and synthesized. This work provides insight on the development of nonmetallic plasmon-sensitized optical materials that can potentially be applied in photocatalysis, optoelectronic, and photovoltaic devices.

One-dimensional ZnO−SnO2 nanofibers with high photocatalytic activity have been successfully synthesized by a simple combination method of sol−gel process and electrospinning technique. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) spectroscopy, nitrogen adsorption−desorption isotherm analysis, UV−vis diffuse reflectance (DR), and photoluminescence (PL) spectroscopy were used to characterize the as-synthesized nanofibers. The results indicated that the ZnO−SnO2 nanofibers with diameters of 100−150 nm consisted of wurtzite ZnO and rutile SnO2. The photocatalytic activity of the ZnO−SnO2 nanofibers for the degradation of rhodamine B (RB) was much higher than that of electrospun ZnO and SnO2 nanofibers, which could be attributed to the formation of a ZnO−SnO2 heterojunction in the ZnO−SnO2 nanofibers and the high specific surface area of the ZnO−SnO2 nanofibers. Notably, the ZnO−SnO2 n...

We present high-yield hydrogen production through selective photocatalytic decomposition of formic acid by using electrospun TiO 2 nanofibers decorated with AuPd bimetallic alloy nanoparticles under simulated sunlight irradiation. By using only 5 mg of the AuPd/TiO 2 nanofibers containing the 0.75% Au and 0.25% Pd, we could achieve an optimal H 2 generation rate of 88.5 μmol h −1 with an apparent quantum yield at 365 nm as 15.6%, which is higher than that of the Pd/TiO 2 and Au/TiO 2 nanofibers by a factor of 1.6 and 4.5, respectively. The enhanced photocatalytic decomposition of formic acid for H 2 generation could be attributed to the stronger electron-sink effect of AuPd alloy nanoparticles, the high selectivity of Pd for the dehydrogenation of formic acid, and the surface plasmon resonance effect of Au. More importantly, we demonstrate that the photocatalytic processes enable re-activation of the AuPd nanoparticles that were poisoned by CO during thermal decomposition of formic acid. As such, the presented AuPd/TiO 2 nanofibers are promising materials for re-generation of H 2 under mild conditions from liquid storage carrier of hydrogen.

Amine-functionalization of TiO2 nanoparticles, through a solvothermal approach, substantially increases the affinity of CO2 on TiO2 surfaces through chemisorption. This chemisorption allows for more effective activation of CO2 and charge transfer from excited TiO2 , and significantly enhances the photocatalytic rate of CO2 reduction into methane and CO.

We report an economic and noble-metal-free artificial photosynthetic system, consisting of g-C3N4 as photosensitizer and photocatalyst, and cobaloxime as co-catalyst, for H2 generation. This system allows for effective electron transfer from excited g-C3N4 to CoIII(dmgH)2pyCl to generate reduced cobaloxime intermediate species for efficient H2 evolution. Transient fluorescence studies reveal that the presence of cobaloxime and TEOA promotes the population of excited electrons to transfer from g-C3N4, which is responsible for the high photocatalytic activity of this g-C3N4-cobaloxime conjugation system. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore) Accepted version

Well-designed hierarchical nanostructures with one dimensional (1D) TiO(2) nanofibers (120-350 nm in diameter and several micrometers in length) and ultrathin hexagonal SnS(2) nanosheets (40-70 nm in lateral size and 4-8 nm in thickness) were successfully synthesized by combining the electrospinning technique (for TiO(2) nanofibers) and a hydrothermal growth method (for SnS(2) nanosheets). The single-crystalline SnS(2) nanosheets with a 2D layered structure were uniformly grown onto the electrospun TiO(2) nanofibers consisted of either anatase (A) phase or anatase-rutile (AR) mixed phase TiO(2) nanoparticles. The definite heterojunction interface between SnS(2) nanosheets and TiO(2) (A or R) nanoparticles were investigated by high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). Moreover, the as-prepared SnS(2)/TiO(2) hierarchical nanostructures as nanoheterojunction photocatalysts exhibited excellent UV and visible light photocatalytic activities for the degradation of organic dyes (rhodamine B and methyl orange) and phenols (4-nitrophenol), remarkably superior to the TiO(2) nanofibers and the SnS(2) nanosheets, mainly owing to the photoinduced interfacial charge transfer based on the photosynergistic effect of the SnS(2)/TiO(2) heterojunction. Significantly, the SnS(2)/TiO(2) (AR) hierarchical nanostructures as the tricomponent heterojunction system possessed stronger photocatalytic activity than the bicomponent heterojunction system of SnS(2)/TiO(2) (A) hierarchical nanostructures or TiO(2) (AR) nanofibers, which was discussed in terms of the three-way photosynergistic effect between SnS(2), TiO(2) (A) and TiO(2) (R) component in the SnS(2)/TiO(2) (AR) heterojunction resulting in the high separation efficiency of photoinduced electron-hole pairs, as evidenced by photoluminescence (PL) and surface photovoltage spectra (SPS).

One-dimensional 2,9,16,23-tetra-nitrophthalocyanine iron(II) (TNFePc)/TiO(2) nanofiber heterostructures have been successfully obtained by a simple combination of electrospinning technique and solvothermal process. The as-obtained products were characterized by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and IR spectrum. The results revealed that the TNFePc nanosheets were successfully grown on the primary TiO(2) nanofibers. And, the coverage density of the secondary TNFePc nanostructures could be controlled by adjusting the experimental parameters. Photocatalytic tests displayed that the H(2)O(2) assisted TNFePc/TiO(2) nanofiber heterostructures (TNFePc/TiO(2)-H(2)O(2)) possessed a much higher degradation rate of methyl orange than the pure TiO(2) and TNFePc/TiO(2) nanofiber without H(2)O(2) under visible light. Moreover, the TNFePc/TiO(2) nanofiber heterostructures could be easily recycled without the decrease of the photocatalytic activity due to their one-dimensional nanostructural property of TiO(2) nanofibers.

The hierarchical tetranitro copper phthalocyanine (TNCuPc) hollow spheres were fabricated by a simple solvothermal method. The formation mechanism was proposed based on the evolution of morphology as a function of solvothermal time, which involved the initial formation of nanoparticles followed by their self-aggregation to microspheres and transformation into hierarchical hollow spheres by Ostwald ripening. Furthermore, the hierarchical TNCuPc hollow spheres exhibited high adsorption capacity and excellent simultaneously visible-light-driven photocatalytic performance for Rhodamine B (RB) under visible light. A possible mechanism for the “aqueous-solid phase transfer and in situ photocatalysis” was suggested. Repetitive tests showed that the hierarchical TNCuPc hollow spheres maintained high catalytic activity over several cycles, and it had a better regeneration capability under mild conditions.

TiO(2)@carbon core/shell nanofibers (TiO(2)@C NFs) with different thinkness of carbon layers (from 2 to 8 nm) were fabricated by combining the electrospinning technique and hydrothermal method. The results showed that a uniform graphite carbon layer was formed around the electrospun TiO(2) nanofiber via C-O-Ti bonds. By adjusting the hydrothermal fabrication parameters, the thickness of carbon layer could be easily controlled. Furthermore, the TiO(2)@C NFs had remarkable light absorption in the visible region. The photocatalytic studies revealed that the TiO(2)@C NFs exhibited enhanced photocatalytic efficiency of photodegradation of Rhodamine B (RB) compared with the pure TiO(2) nanofibers under visible light irradiation, which might be attributed to high separation efficiency of photogenerated electrons and holes based on the synergistic effect between carbon as a sensitizer and TiO(2) with one dimension structure. Notably, the TiO(2)@C NFs could be easily recycled due to their one-dimensional nanostructural property.

In the present work, 2,9,16,23-tetranitrophthalocyanine copper(II) (TNCuPc)/TiO(2) hierarchical nanostructures were successfully fabricated by a simple combination method of electrospinning technique and solvothermal processing. Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD), UV-vis diffuse reflectance (DR), Fourier transform infrared spectrum (FT-IR), X-ray photoelectron spectroscopy (XPS), and thermal gravimetric and differential thermal analysis (TG-DTA) were used to characterize the as-synthesized TNCuPc/TiO(2) hierarchical nanostructures. The results showed that the secondary TNCuPc nanostructures were not only successfully grown on the primary TiO(2) nanofibers substrates but also uniformly distributed without aggregation. By adjusting the solvothermal fabrication parameters, the TNCuPc nanowires or nanoflowers were facilely fabricated, and also the loading amounts of TNCuPc could be controlled on the TNCuPc/TiO(2) hierarchical nanostructural nanofibers. And, there might exist the interaction between TNCuPc and TiO(2). A possible mechanism for the formation of TNCuPc/TiO(2) hierarchical nanostructures was suggested. The photocatalytic studies revealed that the TNCuPc/TiO(2) hierarchical nanostructures exhibited enhanced photocatalytic efficiency of photodegradation of Rhodamine B (RB) compared with the pure TNCuPc or TiO(2) nanofibers under visible-light irradiation.

In this work, V-doped TiO(2) nanofibers with different V contents have been fabricated by an electrospinning technique. The as-prepared nanofibers were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectra, X-ray photoelectron spectroscopy (XPS), and UV-Vis diffuse reflectance (DR) spectroscopy. The results indicated that the V(4+) or V(5+) ions were successfully incorporated into the crystal lattice of anatase TiO(2) nanofibers. Meanwhile, the V doping could extend the visible light absorption of TiO(2) nanofibers. The photocatalytic experiments indicated that the obtained V-doped TiO(2) nanofibers possessed high activity for the photodegradation of organic pollutant methylene blue (MB). Especially, the 1.0 and 5.0 wt.% V-doped TiO(2) nanofibers exhibited the best catalytic activity under visible and ultraviolet (UV) light irradiation, respectively. Also, these nanofibers could be easily recycled without a decrease of the photocatalytic activity.

Nickel sulfide nanoparticles were successfully grown as a cocatalyst on the surface of polymeric g-C3N4 photocatalysts through a hydrothermal method. The NiS2 composition is confirmed by various spectroscopic techniques and electron microscopy. It was found that the presence of NiS2 nanoparticles on the g-C3N4 surface could greatly enhance the photocatalytic activity of g-C3N4 for hydrogen generation under visible-light irradiation. Significantly, the NiS2-loaded g-C3N4 was capable of showing an even higher photocatalytic H2 generation rate than that of Pt-loaded g-C3N4. Such enhanced photocatalytic activities by NiS2-loading could be attributed to the effective charge transfer between g-C3N4 and the attached NiS2 nanoparticles which might also serve as active sites for proton reduction into H2. Our studies demonstrate a promising strategy to develop economic noble-metal-free composites as photocatalysts for efficient solar-to-hydrogen conversion. Accepted version

Core/shell nanofibers of TiO2@carbon embedded by Ag nanoparticles (TiO2@C/Ag NFs) were fabricated by combining the electrospinning technique, the hydrothermal method and an in situreduction approach. The results showed that a uniform graphite carbon layer of approximately 8 nm in thickness was formed around the electrospun TiO2 nanofiber and small Ag nanoparticles (Ag NPs) were dispersed well inside the carbon layer. And, the TiO2@C/Ag NFs had remarkable light absorption in the visible region. The photocatalytic studies revealed that the TiO2@C/Ag NFs exhibited enhanced photocatalytic efficiency of photodegradation of Rhodamine B (RB) and Methyl Orange (MO) compared with the pure TiO2 nanofibers, TiO2@carbon core/shell nanofibers and TiO2/Ag nanofibers under visible light irradiation, which might be attributed to the good light absorption capability and high separation efficiency of photogenerated electron–hole pairs based on the photosynergistic effect among the three components of TiO2, carbon and Ag. And, the TiO2@C/Ag NFs could be easily recycled due to their one-dimensional nanostructural property.

A novel visible photocatalyst of nanostructured 2,9,16,23-tetranitrophthalocyanine copper(II) (CuTNPc) coated on Fe3O4 particles has been successfully fabricated using a simple solvent-thermal process. Scanning electron micrographs (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-vis diffuse reflectance (DR), Fourier transform infrared spectrum (FT-IR), X-ray photoelectron spectroscopy (XPS), were used to characterize the as-synthesized dandelion-like Fe3O4@CuTNPc hierarchical nanostructure. The photocatalytic studies suggested that the dandelion-like Fe3O4@CuTNPc hierarchical nanostructure showed excellent photocatalytic efficiency for the degradation of rhodamine B (RB) and methylene blue (MB) under visible light irradiation. More importantly, the dandelion-like nanostructured Fe3O4@CuTNPc photocatalysts could be effectively separated for reuse by simply applying an external magnetic field. A possible mechanism for the formation of the dandelion-like nanostructured Fe3O4@CuTNPc is suggested.

In this paper, a facile two-step synthesis route combining an electrospinning method and hydrothermal technique has been accepted as a straightforward protocol for the exploitation of Bi4Ti3O12/TiO2 heterostructures which are composed of Bi4Ti3O12 nanosheets on the surface of TiO2 submicron fibers. The thickness of the as-grown nanosheets was about 20 nm and the size of the nanosheets increase with the increase of precursor concentration. Photocatalytic tests display that the Bi4Ti3O12/TiO2 heterostructures possess a much higher degradation rate of rhodamine B (RB) than the unmodified TiO2 submicron fibers under visible light. The enhanced photocatalytic activity can be attributed to the extended absorption in the visible light region resulting from the Bi4Ti3O12 nanosheets, and the effective separation of photogenerated carriers driven by the photoinduced potential difference generated at the Bi4Ti3O12/TiO2 junction interface.