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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]

The activation capacity of molecular oxygen is an important indicator to evaluate the photocatalytic efficiency of photocatalysts. In this paper, WS2 nanosheet was deposited on hyper-crosslinked CTF-1-G (obtained by molecular expansion from covalent triazine framework CTF-1) to form a C-GW heterojunction, which promoted the photodegradation of pollutants and the activation of molecular oxygen. This novel C-GW heterojunction exhibited excellent degradation property for organic pollutants (tetracycline (TC), rhodamine B (RhB)) and activating molecular oxygen under visible light irradiation. Among them, C-GW15 could degrade 98% of 20 ppm TC in 60 min and 99% of 30 ppm RhB in 30 min, and it had the highest hydrogen generation rate and hydrogen production amount in 4 hours, which were 8.74 mmol h−1 g−1 and 34.94 mmol g−1, respectively. Meanwhile, C-GW15 had the strongest 3,3′,5,5′-tetramethylbenzidine oxidation capacity and could generate 1.83 μmol of ˙O2− in 60 min and the production of H2O2 was 20.8 μmol L−1 in 40 min. The results of this study clearly indicated that the combination of WS2 and CTF-1-G can enhance the visible light absorption capacity and photogenerated carrier separation efficiency, thus promoting the photocatalytic performance. Finally, a Z-type photocatalytic mechanism was proposed based on radical capture, molecular oxygen activation experiments and electron spin resonance analysis. These findings will extend the fundamental understanding of the Z-type photocatalytic mechanism and provide new opportunities for the rational design of CTF heterojunctions for the treatment of environmental pollution and clean energy conversion. [ABSTRACT FROM AUTHOR]

Three-dimensional rose-like ZnO (R-ZnO) is an appealing photocatalyst due to its remarkable properties, while it is also essential to boost its current visible light photocatalytic performance. In this study, R-ZnO was prepared by the hydrothermal method, and oxygen vacancies and Ag nanoparticles were introduced by calcining the ZnO precursor in an argon atmosphere and the photoreduction method, respectively, to improve the photocatalytic activity. The prepared Ag/Ar-ZnO exhibits a narrower bandgap of 2.79 eV, highly increased light absorption both in the ultraviolet and visible light regions, and improved charge separation and transfer efficiencies induced by the relatively higher number of oxygen vacancies and the localized surface plasmon resonance (LSPR) effect of the Ag nanoparticles. Therefore, Ag/Ar-ZnO displays a significantly enhanced visible light photocatalytic performance, with a methyl orange (MO) photodegradation rate constant (Kap) that is 2.41 and 3.59 times higher than those of Ag-ZnO and Ar-ZnO, respectively. This research offers an effective way to enhance the photodegradation performance of R-ZnO under visible light irradiation. [ABSTRACT FROM AUTHOR]

Novel two-dimensional (2D) oxides are of great interest for photocatalysis because of their superlative physical features, namely, large surface areas, short charge diffusion pathways, high crystallinity and easy surface modification. However, most 2D oxides suffer from weak visible light absorption and severe photogenerated carrier recombination. Nitrogen doping can successfully narrow the bandgap of 2D oxides but can hardly improve the charge separation. In this work, we pre-dope nitrogen into 2D titanate nanosheets (HTiO), followed by surface processing with solution plasma. By dual modification of nitrogen doping and solution plasma processing (SPP), the modified 2D titanate nanosheets (N-HTiO-SPP) display broad absorption extending to the visible light region and the healing of oxygen vacancies brought about by nitrogen doping. Compared with HTiO and nitrogen doped titanate (N-HTiO), a higher removal rate and mineralization rate towards the photocatalytic degradation of acetaldehyde were achieved over N-HTiO-SPP under solar light. This work provides a powerful way to activate 2D wide bandgap semiconductors for enhanced photocatalytic activity. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) have great potential for producing photoelectrocatalyzed hydrogen and degrading pollutants, owing to several factors such as high porosity and tunable semiconductor-like properties. Wide band gaps, which restrict their use to only UV light induced reactions, and low efficiencies for the separation of photogenerated charge carriers (electrons and holes) pose significant challenges to the widespread applications of MOFs. In this study, a hierarchical hollow Pt@H-UiO-66-NH2/CdS ternary catalyst was designed and synthesized. The immobilized CdS nanoparticles (NPs) in this catalyst endow the MOF H-UiO-66-NH2 with high visible light absorption ability and the Pt NPs serve as electron sinks to improve charge carrier separation. Furthermore, the hierarchical hollow structure of H-UiO-66-NH2 in the composite contributes to boosting light absorption and shortening the distance for charge transfer. As a proof of principle, Pt@H-UiO-66-NH2/CdS catalyzes methylene blue (MB) degradation with a high rate constant of 1.025 × 10−2 and hydrogen production with a rate of 12 810 μmol g−1 h−1, the latter of which is about 2.3, 11.7 and 173 times higher than those of Pt@UiO-66-NH2/CdS, H-UiO-66-NH2/CdS and Pt@H-UiO-66-NH2, respectively. [ABSTRACT FROM AUTHOR]

Highly efficient 2D/2D layered heterostructure of nickel oxide (NiO) and molybdenum sulphide (MoS2) has been fabricated for the photoelectrochemical (PEC) water splitting and degradation of Bromophenol Blue (BPB) under visible light. The XRD spectra confirm mixed characteristic peaks of MoS2 and NiO in the nanocomposite. SEM displays flower-like patterns of pure and composite material with the 2D nanosheets layer structure. The band gap reduction (2.25–1.72 eV) is due to the incorporation of NiO in MoS2 for visible light harvesting. TEM confirms the homogeneous distribution of 2D/2D nanosheets. The excellent interfacial coupling in strong 2D/2D interactions boost the electro and photocatalytic activities. 15.0% NiO showed excellent PEC activity toward OER with maximum photocurrent density of 1.57 mA cm−2, which influenced the overall water splitting at lower potential, ensuring visible photoresponse. The maximum photodegradation performance for highly toxic BPB was achieved by the photocatalyst, which contains 15.0 wt% NiO in NiO/MoS2 composite. It displays the highest conversion efficiency (∼87.0%) for BPB owing to exposed active sites via Mo–Ni–S linkages. Defects in NiO/MoS2 offer favorable reaction dynamics to PEC OER, which are helpful in tuning the band potentials. [ABSTRACT FROM AUTHOR]

The synthesis and development of cost-effective and high-efficiency adsorption-photocatalysis bifunctional treatment agents for uranium-containing wastewater is of great importance. In this work, we successfully synthesized layered double hydroxides (LDHs, NiAl and ZnNiAl) with different nickel coordination environments and investigated the adsorption activity and photocatalytic removal performance of uranium (U(VI)) under visible light. The adsorption experimental results showed that the adsorption capacity of NiAl was about four times that of ZnNiAl, and the excellent adsorption properties of NiAl originated from its large surface area and surface Ni–OH groups, which had a high coordination ability toward U(VI). In addition, NiAl had a narrower band gap than ZnNiAls due to the electronegativity of Ni2+(1.91) being greater than Zn2+(1.65), and NiAl (0.055 h−1) exhibited a higher efficiency of U(VI) photoreduction than ZnNiAl (0.0138 h−1) under visible light. Thus, NiAl showed dual properties of adsorption and photoreduction. In the process of photocatalysis, the photogenerated electrons and generated ˙O2− radicals could reduce the absorbed U(VI) into insoluble UO2(s) and U3O8. Consequently, photocatalytic reduction could further improve the performance of NiAl in removing U(VI) from the solution. NiAl with its low cost and disposal simplicity could be exploited for the decontamination of U(VI), involving surface complexation and photocatalytic reduction. [ABSTRACT FROM AUTHOR]

Layered oxynitrides are promising materials for visible light photocatalysis. However, the conventional method for the synthesis of oxynitrides using ammonia as a nitrogen source is dangerous. In this work, we successfully synthesized two layered tantalum oxynitrides, K1.35LaTa2O6.65N0.35 and K1.4Ca2Ta3O9.6N0.4, via a topochemical nitridation process using urea as a solid nitrogen source. Employing different characterization methods, we determined the structure and composition of layered oxynitrides. Furthermore, using Pt as a co-catalyst, these two layered oxynitrides showed excellent photocatalytic performances under visible light irradiation. In contrast to ammonia, urea process provides easy access for the synthesis of layered oxynitrides and sheds new light on the design of effective visible light-driven photocatalysts. [ABSTRACT FROM AUTHOR]

Zeolites are widely applied in environmental catalysis. They are well known for the long production time at elevated temperature. In this research, photocatalysis has been introduced for the first time into zeolite chemistry to realize an efficient production of Na–A and NaZ-21 zeolites within 8 hours at room temperature. During the synthesis process, g-C3N4 was employed as a visible light photocatalyst, which significantly increased the concentration of hydroxyl radicals (˙OH) and associated superoxide radicals (˙O2−) in the basic media. Both reactive oxygen species (ROS) contributed to the fast synthesis of the zeolite by accelerating Si–O (Al–O) bond breaking and reforming. The research findings have paved a new way for the ROS-dominant fast and green synthesis of zeolites for environmental application. [ABSTRACT FROM AUTHOR]

Charge carrier separation is a very important factor in photocatalysis, and it may be achieved through a variety of paths including the construction of heterojunctions and the formation of surface defects. Herein, we demonstrate the construction of flower-like Ag2WO4/CeO2 heterojunctions (namely ACs) by in situ deposition of Ag2WO4 on the surface of flower-like CeO2 with oxygen defects. The ACs with 2.3%, 3.8%, and 5.3% Ag2WO4 are defined as AC-1, AC-2, and AC-3, respectively, and we compare their photocatalytic removal efficiencies. Under visible light, AC-2 exhibits the highest photocatalytic removal efficiency toward cationic dye RhB and tetracycline (TC). The K value of AC-2 toward RhB degradation is determined to be 0.059 min−1, which is 7.56 and 8.94-fold higher than those of Ag2WO4 (0.0078 min−1) and CeO2 (0.0066 min−1), respectively. Moreover, the K value of AC-2 toward TC degradation (0.021 min−1) is 4.04 and 5.68-fold higher than those of Ag2WO4 (0.0052 min−1) and CeO2 (0.0037 min−1), respectively. Our results clearly demonstrate that the introduction of Ag2WO4 particles stimulates the formation of surface defects of CeO2, improves the visible light absorption, accelerates the charge carrier separation, and consequently boosts the photocatalytic degradation of dyes and drugs. [ABSTRACT FROM AUTHOR]

FeWO4 was synthesized by a simple solvothermal method. The band structure of FeWO4 was investigated on the basis of density functional theory calculations. The FeWO4 photocatalyst showed lower photocatalytic activity for the degradation of doxycycline hydrochloride under visible light irradiation. Kinetic studies using radical scavenger technologies suggested that hydroxyl radicals were the dominant photo-oxidants. In order to enhance the photocatalytic activity of FeWO4, FeWO4 was used to activate peroxymonosulfate to degrade doxycycline hydrochloride under visible light irradiation. The influences of the peroxymonosulfate dosage, doxycycline hydrochloride concentration, inorganic anions, natural organic matter and pH value on activating peroxymonosulfate to degrade doxycycline hydrochloride were investigated in detail. The mechanism of FeWO4 activating peroxymonosulfate was proposed and proved by radical quenching experiments, electron spin resonance analysis, X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy, transient photocurrent responses and cyclic voltammetry. It can be found that the combined activation effects of photo-generated electrons and transition metals on peroxymonosulfate to produce sulfate radicals could enhance the degradation efficiency obviously. [ABSTRACT FROM AUTHOR]

MIL-53Fe was prepared by a simple solvothermal method, and the MIL-53Fe photocatalysts showed low photocatalytic activity for the degradation of tetracycline hydrochloride under visible light irradiation. After combination with TiO2, the photocatalytic activity of MIL-53Fe was enhanced obviously. The enhanced photocatalytic activity of the MIL-53Fe@TiO2 photocatalysts could be attributed to the effective separation of the photogenerated e−/h+ pairs. In order to further enhance the degradation efficiency of MIL-53Fe@TiO2, it was used to activate peroxymonosulfate to degrade tetracycline hydrochloride. The influencing factors on the activation of peroxymonosulfate to degrade tetracycline hydrochloride were investigated in detail. The mechanism of MIL-53Fe@TiO2 activation of peroxymonosulfate was investigated by radical quenching experiments, which proved that holes and sulfate radicals controlled the degradation of tetracycline hydrochloride. Cycle experiments showed that the photodegradation efficiency did not change obviously after the catalyst was recycled three times. This study provided a new way that the synergetic effect of photocatalysis and peroxymonosulfate activation by transition metal was used for efficient photocatalytic degradation in the field of antibiotic removal, hoping to provide new ideas for the development of metal–organic frameworks. [ABSTRACT FROM AUTHOR]

An efficient, one-pot wet chemical synthesis strategy for the preparation of NiO nanoparticles has been reported. The nanostructured NiO has surface bound hexamine and it has emerged as a proficient catalyst for the conversion of carbon dioxide (CO2) into formaldehyde with a maximum turnover number of 369 in the presence of blue LED light. The nano-photocatalyst has shown great catalytic efficiency (in terms of the turnover number) and excellent reusability for the photoreduction of CO2. To the best of our knowledge this will be the first report on photoreduction of CO2 to formaldehyde in water under visible light irradiation using NiO nanoparticles as the photocatalyst. The as-prepared NiO nanomaterial has been thoroughly characterized using several spectroscopic and microscopic techniques, e.g. UV-vis spectroscopy, PXRD, XPS, SEM, FESEM and TEM. The mechanism of formation has been predicted from a detailed FTIR analysis. [ABSTRACT FROM AUTHOR]

High-efficiency sunlight energy usage and low carrier recombination have attracted significant attention for the exploration of novel photocatalyst candidates. In this work, BiOCl nanosheets showing various (001)/(102) facet ratios were synthesized by a simple hydrolysis method under different pH conditions by using BiCl3 as a precursor. The inherent relationship among the morphology, exposure facets and photocatalytic performance of BiOCl was visualized via adjusting the synthesis parameters during the hydrolysis process. The results indicate that the suitable (001)/(102) facet ratio, abundant hydroxyl groups on the surface, and the negative potential surface of BiOCl are important factors for the enhancement of its photocatalytic degradation rate of organic pollutants. Besides, the negative potential surface of BiOCl helps in the adsorption of Rhodamine B (RhB) molecules readily, which act as a sensitizer to widen the response range of BiOCl from ultraviolet light to visible light. The sensitized BiOCl photocatalyst with good matching (001)/(102) crystal planes indicates an excellent photocatalytic behavior, and it can decolorize a RhB solution completely under visible light within 40 min, which is even higher than that of commercial TiO2 under UV light irradiation. This work provides a facile route and good idea for the application of photocatalysis for the removal of cationic pollutants in the wastewater purification field. [ABSTRACT FROM AUTHOR]

Owing to their uniformly separated metal sites and regular structures, Ag(I)-based coordination polymers (CPs) have been considered as promising platforms for plasmonic photocatalysts. Herein, a novel Ag(I)-CP [Ag2(NO2-bdc)(4,4′-bpy)2]·2CH3CN·2.5H2O (JLNU-90, NO2-bdc = 4-nitrophthalic acid, 4,4′-bpy = 4,4′-bipyridine) has been synthesized at room temperature. By using a self-photoreduction strategy, some Ag(I) sites in CPs are reduced to metallic Ag0 and Ag0-doped JLNU-90/x can be constructed under a mercury lamp. Photocatalytic experiments reveal that the JLNU-90/x catalysts show better photocatalytic performance for methylene blue (MB) under visible light in comparison with JLNU-90. The optimal JLNU-90/1.5 has the best performance with a degradation efficiency of 70%. The outstanding photocatalytic behaviour is mainly improved by the surface plasmon resonance (SPR) effect and the fast transfer of photogenerated carriers. The proposed mechanism systematically combines the reactive species and the band gap structures to explain the detailed photocatalytic process on JLNU-90/1.5. [ABSTRACT FROM AUTHOR]