A highly efficient g-C3N4/SiO2 heterojunction: the role of SiO2 in the enhancement of visible light photocatalytic activity.

SiO2, an insulator, hardly has any photocatalytic acitivity due to its intrinsic property, and it is generally used as a hard template to increase the surface area of catalysts. However, in this work, we found that the surface state of the insulator SiO2 can promote the migration of photogenerated charge carriers, leading to the enhancement of the photooxidation ability of graphitic carbon nitride (g-C3N4). A one-pot calcination method was employed to prepare g-C3N4/SiO2 composites using melamine and SiO2 as precursors. The composites present considerably high photocatalytic degradation activities for 2,4-dichlorophenol (2,4-DCP) and rhodamine B (RhB) under visible light (λ > 420 nm) irradiation, which are about 1.53 and 4.18 times as high as those of bulk g-C3N4, respectively. The enhancement of the photocatalytic activity is due to the fact that the introduction of the insulator SiO2 in g-C3N4/SiO2 composites can greatly improve the specific surface area of the composites; more importantly, the impurity energy level of SiO2 can help accelerate the separation and transfer of electron-hole pairs of g-C3N4. Electron paramagnetic resonance (EPR) spectroscopy and trapping experiments with different radical scavengers show that the main active species of g-C3N4 are superoxide radicals, while holes also play a role in photodegradation. For g-C3N4/SiO2-5, besides superoxide radicals and holes, the effect of hydroxyl radicals was greatly improved. Finally, a possible mechanism for the photogenerated charge carrier migration of the g-C3N4/SiO2 photocatalyst was proposed.

Simultaneous Reduction of Vanadium (V) and Chromium (VI) in Wastewater by Nanosized ZnWO4 Photocatalysis.

Vanadium (V, V) and chromium (Cr, VI) are simultaneously photocatalytically reduced to less-toxic V(VI) and Cr(III) by mimetic solar light with ZnWO4 nanoparticles prepared by hydrothermal synthesis. The reduction efficiencies can reach 68.8% for V(V) and 97.3% for Cr(VI) in 3 h, respectively, which are comparable to those by microbial fuel cell technology carried out in over 10 days. The prepared ZnWO4 nanoparticles are characterized by XRD, SEM, EDS, TEM, and Uv-vis-DRS tests. Electrochemical calculation shows high acidity benefits the rapid reduction of V(V) and Cr(VI). In addition, the applied ZnWO4 nanoparticles can be recycled and reused for 5 repeated photocatalytic reduction runs. And after 5 runs, the recycled ZnWO4 nanoparticles can also present good photocatalytic activity with a reduction efficiency of about 60% for V(V) and 90% for Cr(VI). The new procedure on the simultaneous reduction of V(V) and Cr(VI) by photocatalysis may be promisingly applied in contaminated wastewaters, combining the remediation and possible V and Cr recovery.

Synthesis and Visible Photodegradation Enhancement of CdS/mpg-C3N4 Photocatalyst.

A series of visible-light-induced CdS/mpg-C3N4 nanocomposites were fabricated vis the solvothermal method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectroscopy analysis. The results show that CdS nanoparticles are homogenously dispersed on the sheet of mesoporous g-C3N4. The CdS/mpg-C3N4 nanocomposites show much higher visible-light-driven photocatalytic activity than individual mpg-C3N4 and CdS for methylene blue (MB) and phenol degradation. The optimal CdS content with the highest photocatalytic activity is determined to be 40%, which is almost 6.4 and 1.6 times higher than that those of individual mpg-C3N4 and CdS for the degradation of MB, and 12.2 and 2.2 folds for the degradation of phenol. The enhancement in photocatalytic activity and stability should be assigned to the effective separation and transfer of photogenerated charges coming from the well-matched overlapping band-structure between mpg-C3N4 and CdS. Radical trap experiments show that both the holes and O·â»2 are main oxidative species of CdS/mpg-C3N4 for MB degradation under visible light irradiation. Finally, the possible mechanism for the enhancement of the visible light performance is proposed.

Enhancement of visible photocatalytic performances of a Bi2MoO6-BiOCl nanocomposite with plate-on-plate heterojunction structure.

A visible-light-sensitive Bi2MoO6-BiOCl heterojunction photocatalyst was synthesized via a hydrothermal process. The as-prepared Bi2MoO6-BiOCl composite shows an irregular multi-plate structure with length ranging from 100 nm to 1 µm, indicating a possibility of the plate-on-plate structure by placing Bi2MoO6 and BiOCl nanoplates over each other. The Bi2MoO6-BiOCl photocatalyst not only had a good visible-light photocatalytic performance, but also exhibited higher photocatalytic activity than pure BiOCl and Bi2MoO6. The optimal Bi2MoO6 content for the photocatalytic activity of the Bi2MoO6-BiOCl composites is 30%. Compared to pure Bi2MoO6 the photoactivity of the Bi2MoO6-BiOCl composites is almost 2.0 times higher for the RhB photodegradation, and 1.5 times higher for the phenol photodegradation under visible light irradiation. The photocatalytic mechanism was elucidated via active species trapping experiments and ESR. The ˙OH and ˙O2(-) played the key roles in the degradation of RhB via the Bi2MoO6-BiOCl composite. Finally, the possible charge transfer mechanism of the enhanced visible light photocatalytic activity was proposed.

Ultrathin BiOCl-OV/CoAl-LDH S-scheme heterojunction for efficient photocatalytic peroxymonosulfate activation to boost Co (IV)=O generation.

Sustainable and rapid production of high-valent cobalt-oxo (Co(IV)=O) species for efficiently removing organic pollutants is challenging in permoxymonosulfate (PMS) based advanced-oxidation-processes (AOPs) due to the limitation of the high 3d-orbital electronic occupancy of Co and slow conversion from Co(III) to Co(II). Herein, S-scheme BiOCl-OV/CoAl-LDH heterojunction were constructed by ultrathin BiOCl with the oxygen-vacancy (OV) self-assembled with ultrathin CoAl-LDH. OV promoted the formation of charge transfer channel (Bi-O-Co bonds) at the interface of the heterojunction and reduced electron occupation of the Co 3d-orbital to facilitate the generation of Co(IV)=O in the BiOCl-OV/CoAl-LDH/PMS/Visible-light system. S-scheme heterojunction accelerated the photogenerated electrons to allow rapid conversion of Co(III) to Co(II), promoting the fast two-electron transfer from Co(II) to Co(IV)=O. Consequently, the developed BiOCl-OV/CoAl-LDH/PMS/Visible-light system showed excellent degradation efficiency for most of organic pollutions, and exhibited very high removal capability for the actual industrial wastewater. This study provides a new insight into the evolution of Co(IV)=O and the coordinative mechanism for photocatalysis and PMS activation.

Design of ultrathin CoAl-LDHs/ZnIn2S4 with strong interfacial bonding and rich oxygen vacancies for highly efficient hydrogen evolution activity.

Designing a semiconductor-based heterostructure photocatalyst is very important way to enhance the hydrogen production activity. Here, a novel 2D/2D CoAl-LDHs/ZnIn2S4 S-scheme heterostructure with an ultrathin structure was synthesized by electrostatic attraction between CoAl-LDHs and ZnIn2S4 nanosheets. The presence of oxygen vacancies in the monolayer CoAl-LDHs nanosheet promotes the formation of Co-SX bonds, which serve as charge transfer channels at the interface of the CoAl-LDHs/ZnIn2S4 heterostructure. The ultrathin CoAl-LDHs/ZnIn2S4 exhibits broadened light absorption in the near-infrared range due to the occurrence of Co-SX chemical bonds. The CoAl-LDHs/ZnIn2S4 with a mass ratio of 1:2 demonstrated the highest photocatalytic hydrogen evolution activity (1563.64 µmol g-1 h-1) under the simulated sunlight, which is 4.6 and 9.7 times than that of the ZnIn2S4 and CoAl-LDHs/ZnIn2S4(bulk), respectively. The enhanced photocatalytic activity of ultrathin 2D/2D CoAl-LDHs/ZnIn2S4 should attributed to the shorter carriers path that benefit from the ultrathin structure and the quicker photogenerated charge transfer and the S-scheme migration pathway accelerated by the charge channel of Co-SX bonds. These new ideas should be inspiring for the design and construction of heterostructures for higher photocatalytic hydrogen evolution activity.

In Situ Synthesis of Bi2MoO6/Bi2SiO5 Heterojunction for Efficient Degrading of Persistent Pollutants.

Photocatalytic degradation is an environmentally friendly way to eliminate environmental pollution. Exploring a photocatalyst with high efficiency is essential. In the present study, we fabricated a Bi2MoO6/Bi2SiO5 heterojunction (BMOS) with intimate interfaces via a facile in situ synthesis method. The BMOS had much better photocatalytic performance than pure Bi2MoO6 and Bi2SiO5. The sample of BMOS-3 (3:1 molar ratio of Mo:Si) had the highest removal efficiency by the degradation of Rhodamine B (RhB) up to 75% and tetracycline (TC) up to 62% within 180 min. The increase in photocatalytic activity can be attributed to constructing high-energy electron orbitals in Bi2MoO6 to form a type II heterojunction, which increases the separation efficiencies of photogenerated carriers and transfer between the interface of Bi2MoO6 and Bi2SiO5. Moreover, electron spin resonance analysis and trapping experiments showed that the main active species were h+ and •O2- during photodegradation. BMOS-3 maintained a stable degradation capacity of 65% (RhB) and 49% (TC) after three stability experiments. This work offers a rational strategy to build Bi-based type II heterojunctions for the efficient photodegradation of persistent pollutants.

A Lead-Free 0D/2D Cs3Bi2Br9/Bi2WO6 S-Scheme Heterojunction for Efficient Photoreduction of CO2.

Photocatalytic reduction of CO2 into valuable hydrocarbon fuels is one of the green ways to solve the energy problem and achieve carbon neutrality. Exploring photocatalyst with low toxicity and high-efficiency is the key to realize it. Here we report a lead-free halide perovskite-based 0D/2D Cs3Bi2Br9/Bi2WO6 (CBB/BWO) S-scheme heterojunction for CO2 photoreduction, prepared by a facile electrostatic self-assembly approach. The CBB/BWO shows superior photoreduction of CO2 under visible light with CO generation rate of 220.1 µmol·g-1·h-1, which is ∼115.8 and ∼18.5 times higher than that of Cs3Bi2Br9 perovskite quantum dots (CBB PQDS) and Bi2WO6 nanosheets (BWO NS), respectively. The improved photocatalytic activity can be attributed to the tight 0D/2D structure and S-scheme charge transfer pathway between the Cs3Bi2Br9 PQDS and atomic layers of the Bi2WO6 NS, which shortens transmission distance of photogenerated carriers and boosts efficient separation and transfer of the carriers. This work provides insight in manufacturing potential lead-free perovskite-based photocatalysts for achieving carbon neutrality.

Preparation of TiO2/Black Talc Composite Photocatalyst and the Research on Its Adsorption-Degradation Coupling Effects.

In this paper, a TiO2/black talc composite photocatalyst was prepared by the sol-gel method using TBOT as titanium source and black talc as carrier. Rhodamine B was used as the targeted pollutant to study the adsorption role of carbon in black talc. The results showed that with the adsorption-degradation cycles, the illumination time can be reduced by 40%. The adsorption rate and degradation rate of the composite photocatalyst was also increased. The degradation rate of Rhodamine B reached more than 95%, which fully shows the synergistic effect between TiO2 nanoparticles and black talc. In this way, the adsorption-degradation coupling of the photocatalyst could be realized.

The effects of Baduanjin exercise on fatigue and quality of life in patients with heart failure: A randomized controlled trial.

AIMS: The purpose of this study was to examine the effects of Baduanjin exercise on fatigue and quality of life in patients with heart failure. METHODS: The study was a randomized controlled trial. Participants diagnosed with heart failure were recruited from two large medical centers in northern Taiwan. Participants were randomly assigned to the intervention ( n=39) or control ( n=41) groups. Patients in the intervention group underwent a 12-week Baduanjin exercise program, which included Baduanjin exercise three times per week for 12 weeks at home, a 35-minute Baduanjin exercise demonstration video, a picture-based educational brochure, and a performance record form. The control group received usual care and received no intervention. Fatigue and quality of life were assessed using a structural questionnaire at baseline, four weeks, eight weeks, and 12 weeks after the intervention. RESULTS: Participants in the Baduanjin exercise group showed significant improvement in fatigue ( F=5.08, p=0.009) and quality of life ( F=9.11, p=0.001) over time from baseline to week 12 after the intervention. Those in the control group showed significantly worse fatigue ( F=3.46, p=0.033) over time from baseline to week 12 and no significant changes in quality of life ( F=0.70, p=0.518). Compared to the control group, the exercise group demonstrated significantly greater improvement in fatigue and quality of life at four weeks, eight weeks, and 12 weeks. CONCLUSIONS: This simple traditional exercise is recommended for Taiwanese patients with heart failure in order to improve their fatigue and quality of life.

Preparation of black-pearl reduced graphene oxide-sodium alginate hydrogel microspheres for adsorbing organic pollutants.

The black-pearl reduced graphene oxide-sodium alginate (rGO-SA) hydrogel microspheres are prepared by the external emulsification and thermal reduction method, which are characterized by scanning electron microscope (SEM) and X-ray Diffraction (XRD). Sodium alginate (SA) serves as a template to form a 3D porous network structure, which can prevent the agglomeration and restacking of rGO sheets efficiently. The size of hydrogel microsphere can be controlled by adjusting the size of the liquid drop. The effects of rGO content (wt%), contact time, initial concentration of phenol, adsorption temperature and adsorption dose on the adsorption capacity of rGO-SA microspheres are investigated. The kinetics and isotherm data are well described by the pseudo-second-order kinetic model and the Langmuir equation, respectively. Thermodynamic results demonstrate the spontaneous and endothermic nature of adsorption. This rGO-SA microsphere exhibits the favorable adsorption performance for phenol, BPA and tetracycline. The rGO-SA microsphere might be a potential candidate for efficient adsorbents in water treatment.

Highly Performance Core-Shell TiO2(B)/anatase Homojunction Nanobelts with Active Cobalt phosphide Cocatalyst for Hydrogen Production.

In this paper, a highly efficient core-shell structure of TiO2(B)/anatase photocatalyst with CoP cocatalyst has been synthesized via hydrothermal processes and a mechanical milling method. The designed core-shell TiO2(B)/anatase photocatalysts exhibit excellent performance by compared with pure TiO2(B) and anatase phase. With the participation of CoP particles, there is drastically enhanced  photocatalytic activity of TiO2(B)/anatase, and the H2-production rate can be up to 7400 µmol·g-1, which is about 3.2 times higher than TiO2(B)/anatase photocatalyst. The improved activity is attributed to the contribution of the well-matched core-shell structure and cooperative effect of CoP cocatalyst. The photogenerated holes of anatase can migrate more promptly to the adjacent TiO2(B) core than the photogenerated electrons, which result in an accumulation of electrons in the anatase, and CoP nanoparticles can contribute significantly to transferring electrons from the surface of TiO2(A). It was found that the efficient separation of electron-hole pairs greatly improved the photocatalytic hydrogen evolution in water under UV light irradiation.

Synthesis and characterization of the ZnO/mpg-C3N4 heterojunction photocatalyst with enhanced visible light photoactivity.

The ZnO/mpg-C3N4 composite photocatalyst with high visible light activity was successfully synthesized by a facile solvothermal method and characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and UV-vis diffuse reflectance spectroscopy (DRS). The results indicated that ZnO particles dispersed uniformly on the mpg-C3N4 sheet. The photocatalytic activity of ZnO/mpg-C3N4 for photodegradation of MB was much higher than that of pure mpg-C3N4 both under the visible light and simulated solar irradiation. The optimal ZnO content for the photocatalytic activity of the ZnO/mpg-C3N4 composites is 24.9%, which is almost 2.3 times as high as that of pure mpg-C3N4 under visible light, and 1.9 times higher than that under simulated solar irradiation. The enhancement in photocatalytic activity should be assigned to the effective separation and transfer of photogenerated charges coming from the well-matched overlapping band-structure between mpg-C3N4 and ZnO. Radical trap experiments show that both ZnO/mpg-C3N4 composites and mpg-C3N4 have the same photodegradation mechanism, and the holes are their main oxidative species for MB degradation.

Selective capture of iodide from solutions by microrosette-like δ-Bi2O3.

Radioactive iodine isotopes that are produced in nuclear power plants and used in medical research institutes could be a serious threat to the health of many people if accidentally released to the environment because the thyroid gland can absorb and concentrate them from a liquid. For this reason, uptake of iodide anions was investigated on microrosette-like δ-Bi2O3 (MR-δ-Bi2O3). The MR-δ-Bi2O3 adsorbent showed a very high uptake capacity of 1.44 mmol g(-1) by forming insoluble Bi4I2O5 phase. The MR-δ-Bi2O3 also displayed fast uptake kinetics and could be easily separated from a liquid after use because of its novel morphology. In addition, the adsorbent showed excellent selectivity for I(-) anions in the presence of large concentrations of competitive anions such as Cl(-) and CO3(2-), and could work in a wide pH range of 4-11. This study led to a new and highly efficient Bi-based adsorbent for iodide capture from solutions.

Synthesis and characterization of TiO2 pillared montmorillonites: application for methylene blue degradation.

TiO2 pillared clay composites were prepared by modifying of montmorillonite (Mt) with cetyl-trimethyammoniumbromide (CTAB) and then using an acidic solution of hydrolyzed Ti alkoxide to intercalate into the interlayer space of the organic modified Mt. The as-prepared materials were characterized by XRD, FTIR, TEM, SEM TG-DTA, specific surface area and porosity measurements. The composites had a porous delaminated structure with pillared fragments and well dispersed TiO2 nanoparticles. Introduction of CTAB into the synthetic system accelerated the hydrolysis and condensation of the Ti source, which promoted TiO2 formation. In addition, the CTAB also significantly increased the porosity and surface area of the composites. A number of anatase particles, with crystal sizes of 5-10 nm, were homogenously distributed on the surface of the Mt as the result of the templating role of CTAB. The resultant TiO2 pillared Mt exhibited good thermal stability as indicated by its surface area after calcination at 800°C. No phase transformations from anatase to rutile were observed even under calcination at 900°C. The grain size of the anatase in prepared sample increased from 2.67 nm to 13.42 nm as the calcination temperature increased from 300°C to 900°C. The photocatalytic performance of these new porous materials was evaluated by using methylene blue degradation. The composite exhibited better photocatalytic property than P 25. The maximum removal efficiency of this composite was up to 99% within 60 min.

Synthesis and photocatalytic performances of the TiO2 pillared montmorillonite.

TiO(2) pillared clay materials were prepared by montmorillonite (Mt) and acidic solutions of hydrolyzed Ti alkoxides in the presence of high-molecular-weight polyoxypropylene (POP)-backboned di-quaternary salts (POP). The as-prepared materials were characterized by means of XRD, FTIR, TG-DTA, XRF, specific surface area and porosity determinations, TEM and SEM, respectively. The experiments showed that the resulting material was a porous delaminated structure containing pillared fragments and nano-scaled TiO(2) particles well dispersed among each other. Introducing polymer surfactant POP as an expanding agent of Mt cannot only promote the formation of the delaminated structure, but significantly improve the porosity and surface area of the composites. The resulting TiO(2) pillared Mt exhibited a good thermal stability as indicated by its surface area after calcination at 800 °C. No phase transformation from anatase to rutile was observed even under calcination at 900 °C. The grain size of anatase in as-prepared sample decreased with the increase of the POP concentration, but increased with the increment of calcination temperature. The photocatalytic performances of these new porous materials were evaluated by using methylene blue degradation. The composite solid exhibited superior photocatalyic property and the maximum removal efficiency was up to 98% within 90 min.

N-doped P25 TiO2-amorphous Al2O3 composites: one-step solution combustion preparation and enhanced visible-light photocatalytic activity.

Nitrogen-doped Degussa P25 TiO2-amorphous Al2O3 composites were prepared via facile solution combustion. The composites were characterised using X-ray diffraction, high-resolution transmission microscopy, scanning electron microscopy, nitrogen adsorption-desorption measurements, X-ray photoelectron spectroscopy, UV-vis light-diffusion reflectance spectrometry (DRS), zeta-potential measurements, and photoluminescence spectroscopy. The DRS results showed that TiO2 and amorphous Al2O3 exhibited absorption in the UV region. However, the Al2O3/TiO2 composite exhibited visible-light absorption, which was attributed to N-doping during high-temperature combustion and to alterations in the electronic structure of Ti species induced by the addition of Al. The optimal molar ratio of TiO2 to Al2O3 was 1.5:1, and this composite exhibited a large specific surface area of 152 m2/g, surface positive charges, and enhanced photocatalytic activity. These characteristics enhanced the degradation rate of anionic methylene orange, which was 43.6 times greater than that of pure P25 TiO2. The high visible-light photocatalytic activity was attributed to synthetic effects between amorphous Al2O3 and TiO2, low recombination efficiency of photo-excited electrons and holes, N-doping, and a large specific surface area. Experiments that involved radical scavengers indicated that OH and O2- were the main reactive species. A potential photocatalytic mechanism was also proposed.