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In this paper, three-dimensional TiO2 nanoflowers (NFs) were prepared by a facile hydrothermal method, and Ag3PO4 was grown in situ following alkali treatment to design and synthesize a Ag3PO4/OH/TiO2 catalyst with excellent photocatalytic activity under visible light. The test results show that the photocatalytic degradation performance of TiO2 NFs after alkali treatment and Ag3PO4 loading is significantly improved. This is because the alkali treatment and the introduction of Ag3PO4 can provide a large amount of –OH, which can be converted to ˙OH under UV irradiation, followed by an increase in the number of active radicals to enhance the photocatalytic degradation performance. Meanwhile, the introduction of Ag3PO4 can effectively improve the light absorption ability of the photocatalyst. Moreover, the in situ growth of Ag3PO4 on TiO2 NFs can construct a high-quality Ag3PO4/TiO2 heterojunction to promote the charge separation and transport. Therefore, the degradation rate of Ag3PO4/OH/TiO2 can reach 90% after 30 min for degrading 3 mg L−1 RhB under visible light. The Ag3PO4/OH/TiO2 photocatalyst designed in the present work provides a new tool for the degradation of organic dyes. [ABSTRACT FROM AUTHOR]

Enhancing the piezoelectric polarization strength of materials to promote the photogenerated carrier separation is of great significance for piezoelectric polarization-assisted photoelectrochemical (PEC) water splitting. In this paper, P-BiFeO3 composite photoelectrodes were synthesized by modifying BiFeO3 photoelectrodes with phosphate ions. The maximum photocurrent density of the P-BiFeO3 composite photoelectrodes could reach 0.87 mA cm−2 at 1.23 V vs RHE, which is significantly enhanced compared to the BiFeO3 photocurrent. The enhanced photoelectrochemical activity of the phosphate ion-modified BiFeO3 photoelectrodes may be attributed to the increased visible light absorption and larger active area due to the presence of phosphate groups. Furthermore, the photocurrent density of the P-BiFeO3 composite photoelectrodes after the introduction of the piezoelectric polarisation field reached 2.58 mA cm−2 at 1.23 V vs RHE, which was 2.2 times higher than that of BiFeO3 (1.17 mA cm−2). The presence of phosphate groups on the surface of BiFeO3 photoelectrodes can improve their asymmetry and increase their piezoelectric polarisation intensity, further enhancing the PEC water splitting performance of the material. This study provides a strategy for the design of highly active photoanodes with ionic modification to enhance the piezoelectric polarisation of the material to improve PEC water splitting. [ABSTRACT FROM AUTHOR]

Promoting the separation of photoelectrons and holes can enhance the photocatalytic performance of photocatalysts. The combination of photocatalysts with piezoelectric materials is an effective way to improve the photocatalytic performance. In this paper, the heterogeneous structure of PZT/Ag2O is proposed, which can effectively improve its photocatalytic degradation performance through the piezoelectric effect. RhB degradation experiments were conducted under ultrasonic vibration and visible light irradiation to evaluate the photocatalytic performance of PZT/Ag2O. It is worth noting that PZT/Ag2O showed excellent piezo-/photocatalytic activity, and the degradation rate of RhB within 60 min was 96.31%, which was higher than those achieved under ultrasonic vibration (55.98%) and visible light irradiation (65.14%). The improved performance is due to the heterojunction construction widening the optical response range, while the piezoelectric effect provides a built-in polarization field to improve the separation efficiency of photogenerated electrons and holes. This study provides an efficient and feasible piezo-/photocatalyst for the treatment of pollutants. It is helpful to understand the mechanism of the piezoelectric effect and improve the photocatalytic performance. [ABSTRACT FROM AUTHOR]

The heterojunction structure of semiconductor photocatalysts is significant for making full use of their capabilities for organic molecules and dye degradation. In this paper, we present a heterogeneous junction composite fabricated with hybrid phase TiO2 and g-C3N4 for methylene blue (MB) removal through adsorption and photocatalytic degradation. The heterogeneous junction system was prepared by hydrothermal treatment with a subsequent pyrolysis process. The variation of the proportion and lattice structure of hybrid phase TiO2 in the synthesized catalysts was analyzed by refinement. Adsorption experiments showed that the maximum adsorption capacity of TiO2/g-C3N4 (1 : 10) was 1667 mg g−1, which was 45.97 times and 63.78 times higher than that of TiO2 and g-C3N4, respectively. In the photodegradation process, the TiO2/g-C3N4 (1 : 10) photocatalyst shows a removal rate of MB of 100 mg L−1, which was as high as 96.262%, significantly higher than that of pure TiO2 and g-C3N4. Brunner–Emmett–Teller (BET) measurements and Fourier transform infrared spectroscopy (FTIR) showed that the adsorption of MB onto TiO2/g-C3N4(1 : 10) was chemical adsorption, and ˙OH, which acts as an active substance, was found to play a major role in the photocatalytic degradation process. Overall, the developed hybrid phase TiO2/g-C3N4 heterojunction composite may be beneficial for the treatment of water pollution. [ABSTRACT FROM AUTHOR]

In this paper, a series of BN/NTCDA photocatalysts have been prepared using a simple calcination method and their photocatalytic performance under visible light irradiation is studied with tetracycline (TC) as the target pollutant. When the ratio of BN and NTCDA is 100 : 1 and the temperature is 350 °C, the sample (BN/NTCDA (100 : 1)) has the highest adsorption efficiency (28.65%) and photodegradation efficiency (51.54%) for TC. The characterization results of XRD, FTIR, XPS, TEM, and 1H NMR show that BN/NTCDA (100 : 1) is a BN-based photocatalytic material, which is likely formed through the reaction of the surface hydroxyl group of BN and the anhydride of NTCDA. The band gap of BN is about 4.11 eV, and the band gap of NTCDA is 2.67 eV. So, the electron is firstly excited from the VB of NTCDA to its CB, and then the electron in the VB of BN is excited into the empty VB of NTCDA, implying that TC is degraded by photoactive species (˙O2−, h+ and ˙OH) from the VB of BN and CB of NTCDA. The capture experiment of photoactive species suggests that ˙O2− makes the main contribution to TC photodegradation, followed by h+, ˙OH. After five recycle experiments, BN/NTCDA (100 : 1) still has 77.32% removal efficiency for TC. The removal efficiency (80.19%) of BN/NTCDA (100 : 1) is higher than that of TiO2 (75.63%) and g-C3N4 (24.44%). This work contributes to the development of novel metal-free-photocatalysts and the application of photocatalytic technology to the removal of antibiotics. [ABSTRACT FROM AUTHOR]

In this paper, Eu/F co-doped bismuth vanadate photocatalysts with different doping ratios were prepared by a hydrothermal method, and their microscopic morphology, crystal structure, light absorption and photocatalytic performance were investigated. Part of the F in the Eu/F co-doped samples might be doped to replace O in the BiVO4 lattice, while Eu3+ ions replaced Bi3+ ions, which led to a difference in the morphology and internal structure. XRD and Raman spectroscopy characterization showed that the crystal structures of the samples were all monoclinic scheelite type, and contained a certain tetragonal scheelite type, and the crystallinity was good. The Eu/F co-doped samples exhibited better photoactivity under UV-Vis light. The recombination rate of the photogenerated carriers in the Eu/F co-doped samples was obviously reduced, but it showed a serious concentration dependence on the doping species. Under visible light irradiation, Eu/F co-doped samples (R = 0.75) had the best degradation effect on methylene blue (MB). In addition, the degradation mechanism of the photocatalyst was also explored. ˙O2− and h+ were the main active species affecting the degradation of MB by Eu/F–BiVO4. [ABSTRACT FROM AUTHOR]

The development of high-efficiency photocatalytic materials responsive to visible light is one of the most effective ways to address the environmental threats posed by organic dyes in industrial wastewater. In this paper, novel visible-light-responsive nitrogen–sulfur co-doped carbon quantum dots modified ZnO (ZnO/N,S-CQDs) composites with a significantly enhanced photocatalytic degradation performance of Rhodamine B (RhB) were successfully synthesized. Under visible light, the photocatalytic degradation efficiency reached 98.7% over the optimal composite. Besides, the degradation obeyed the pseudo-first-order kinetics model with a photocatalytic rate constant (k) of 0.0473 min−1, which was around 3.71 times higher than that of pure ZnO nanoparticles (0.01273 min−1). In addition, the morphology, size and elemental composition of the ZnO/N,S-CQDs were characterized using TEM, SEM, XRD, FT-IR, and XPS which confirmed the successful synthesis of the composites. Photoluminescence (PL) and transient photocurrent response results indicated an increase in the carrier separation efficiency of ZnO/N,S-CQDs. Based on the active species removal experiment, superoxide radicals (˙O2−) played a leading role in the photocatalytic reactions and a possible photocatalytic degradation mechanism was revealed. These further demonstrate that the N,S-CQDs with varying properties contributed significantly to the enhanced photocatalytic activity of ZnO. Overall, the present method follows the principle of green economy, and novel N,S-CQDs provide a feasible approach for the development of photocatalytic performance of ZnO. [ABSTRACT FROM AUTHOR]

BiVO4, as a visible light catalyst, produces photogenerated electrons and photogenerated holes that are easy to recombine. In this paper, a BiVO4/Ag2O composite was prepared to promote the separation of photogenerated carriers of BiVO4. Compared with BiVO4, the properties and photocatalytic activity of BiVO4/Ag2O were obviously improved. The improvement of BiVO4/Ag2O was reflected in the better separation of photogenerated electrons and photogenerated holes, higher UV-visible maximum absorption wavelength, and stronger ability to degrade doxycycline. The effects of Ag2O on the crystal structure, the morphology and the binding energy of BiVO4 were analyzed by XRD, XPS and SEM, and the existence of a heterojunction in BiVO4/Ag2O was confirmed. The results of capture experiments showed that the photocatalytic processes of BiVO4 and BiVO4/Ag2O produced hydroxyl radicals (˙OH), holes (h+) and superoxide radicals (˙O2−). However, the contribution of active species was different in the two systems. The degradation pathways and intermediate products of doxycycline were analyzed by UPLC-QTOF. This work proposed a new method for the preparation of BiVO4/Ag2O particles with remarkable photocatalytic activity, and provided a reference for the degradation of doxycycline. [ABSTRACT FROM AUTHOR]

In this study, Z-scheme Cr2O3–Fe3O4/C hetero-nanostructure polyhedra are prepared using the amine-functionalized metal–organic framework NH2-MIL-101(Fe) as the precursor through a simple hydrothermal method and impregnation–calcination route. Systematic characterization was conducted on the phase structure, morphology, optical/electrochemical properties and the photocatalytic performance exhibited by the magnetic Cr2O3–Fe3O4/C samples. As observed from the results, Congo red (CR) degradation rates of the magnetic polyhedron-like Cr2O3–Fe3O4/C hetero-nanostructures under visible light are found to be nearly 1.86 and 1.21 times higher than those achieved by Cr2O3 and Fe3O4/C samples, respectively. Complying with the results achieved by the active specie tests, superoxide radicals could be the major active species in the CR photocatalytic degradation due to graphite carbon with high conductivity. On this basis, a model Z-scheme photogenerated carrier transfer system was developed. In the present paper, an approach for developing and designing Z-scheme hetero-nanostructure photocatalysts for purifying wastewater is presented. [ABSTRACT FROM AUTHOR]

In this paper, a novel pristine carbon nitride (np-CN) with hollow capsule-like morphology was facilely prepared by the thermal polymerization of melamine and cyanuric chloride at 550 1C in air for 4 h. Then, modified carbon nitride (CN-P4mg) micro-flakes with zigzag edges were synthesized by the copolymerization of melamine, cyanuric chloride, and triaminotriphenylamine with a mass fraction of 0.13%. Analysis of the microstructure, surface state, porosity, and optoelectronic properties of the two samples indicates that CN-P4mg has a larger specific surface area and a lower bandgap than np-CN. Under visible light, CN-P4mg displays enhanced photocatalytic performance for the generation of hydrogen compared to that of np-CN and bulk graphite carbon nitride (g-C3N4). The photocatalytic hydrogen evolution rate of CN-P4mg reaches 16897.3 mmol g-1 h-1, which is 1.84 times that of np-CN and 72 times that of bulk g-C3N4. The experimental results confirm that the addition of triaminotriphenylamine provides a modified design for developing metal-free carbon nitride derivatives and a new route to study efficient photocatalytic materials. [ABSTRACT FROM AUTHOR]

In this paper, we designed and synthesized a novel pH and NIR light responsive UCNP/TiO2/Cur@ZIF-8 nano-composite. The newly synthesized nano-platform was characterized using spectroscopic methods. Here, upconversion nanoparticles (UCNPs) and titanium dioxide nanoparticles (TiO2 NPs) were encapsulated to upconvert energy through the photosensitizing phenomenon where the chemotherapeutic agent curcumin (Cur) and TiO2 synergistically achieved therapeutic effects. At first, ZIF-8 decomposed in the acidic microenvironment of tumors that assisted TiO2 NPs to efficiently convert the irradiated near infrared (NIR) 808 nm light into UV visible light, thus producing a large number of reactive oxygen species to effectively inhibit tumor growth. Furthermore, in vitro and in vivo data demonstrated that UCNP/TiO2/Cur@ZIF-8 is an excellent nanoplatform that can be used as NIR-mediated photodynamic as well as chemotherapeutic therapy for tumors. [ABSTRACT FROM AUTHOR]

A novel CdS@TiO2@C/Ti3C2 composite as a high-efficiency photocatalyst for the degradation of tetracycline hydrochloride (TC-HCl) was fabricated by in situ oxidizing two-dimensional (2D) layered transition metal Ti3C2 MXene and subsequently compounding with CdS nanoparticles (NPs) via a two-step hydrothermal method. Benefitting from the in situ oxidation of Ti3C2 MXene, the derived TiO2@C/Ti3C2 composites possess excellent interface contact and uniform morphology distribution. Furthermore, the in situ grown TiO2 displays a nanosheet (NS) structure with high-energy (001) facets, which could bring about unique surface heterojunctions between the (101) and (001) facets of the TiO2 NSs. On the above basis, CdS NPs are introduced to effectively improve the light-harvesting ability in the visible region due to the narrow band gap and enlarged surface area. Meanwhile, the separation and transfer efficiencies of photo-generated carriers are significantly enhanced by the synergistic effect of the C/Ti3C2 matrix, surface heterojunctions of the TiO2 NSs and heterojunctions of CdS/TiO2. Therefore, the CdS@TiO2@C/Ti3C2 composites display remarkably enhanced photocatalytic ability for TC-HCl degradation under the irradiation of visible light, and the CdS@TiO2@C/Ti3C2-2 sample exhibits optimal photodegradation efficiency with a value of 85% within 60 min, which is 8.5 times higher than that of the TiO2@C/Ti3C2 sample. Additionally, the corresponding improved mechanism is also deeply discussed in the present paper. [ABSTRACT FROM AUTHOR]

The development of high-efficiency and low-cost photocatalysts for hydrogen production reactions is very important to solve energy problems. In this paper we study the photocatalytic H2 evolution activity of a CeO2/CoS2 heterojunction catalyst under visible light. Characterization studies such as XRD and XPS proved the successful synthesis of a CeO2/CoS2 catalyst. The composite catalyst with a CeO2 and CoS2 mass ratio of 1 : 20 had the best activity, and the hydrogen evolution rate reached 5172.20 μmol g−1 h−1. BET and UV-Vis DRS characterization showed that the introduction of CeO2 not only increased the specific surface area of the composite catalyst, but also improved the response of the photocatalyst to visible light. In addition, PL and electrochemical experiments showed that the electrons and holes of the CeO2/CoS2 catalyst could be quickly separated and transferred, thereby accelerating the kinetics of the hydrogen evolution reaction. This work provided an experimental basis for designing a composite photocatalyst with high stability and hydrogen production activity. [ABSTRACT FROM AUTHOR]