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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]

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]

It is essential to design and fabricate semiconductor-based photocatalysts with excellent activity to split H2O into H2 and O2 using sunlight because of the depletion of fossil resources and environmental pollution. LaVO4 is a visible light catalyst with a narrow band gap, satisfactory stability, and a low price. Therefore, in this work, alkali metal-doped LaVO4 was manufactured. Alkali metal-modified LaVO4 was prepared by a hydrothermal method as a photocatalyst for water splitting under visible light illumination, and a series of characterizations was carried out. The results showed that alkali metal doping improved the catalytic performance of pure LaVO4 and mainly optimized the hydrogen and oxygen production of Na-doped LaVO4 so that a maximum H2 and O2 evolution of 2.83 and 0.71 mmol g-1 h-1, respectively was obtained. The superior photocatalytic activity of Na-doped LaVO4 was mainly attributed to synergistic effects, including the extended visible-light response and improved charge separation. This study provides a new idea for the design of a highly efficient LaVO4-based water-cracking photocatalys.t. [ABSTRACT FROM AUTHOR]

A novel MOF-derived Mn2O3-decorated MoS2-graphene (MMG) composite was prepared via a facile hydrothermal method. The synthesized MMG composite was characterized through PXRD, FT-IR spectroscopy, DRS, TEM, FESEM, XPS and PL techniques. The prepared pure Mn2O3 exhibits a nano-chain-like agglomerated morphology with an average particle size of 50 nm distributed on the MoS2 and graphene layer as indicated by TEM images. DRS studies reveal a band gap of 1.22 eV for the MMG hybrid, demonstrating that the MMG hybrid can be used as a visible light–active photocatalyst. The study shows that the MMG-3 catalyst is excellent for the degradation of penicillin G under visible light with a rate constant (kapp) of 1.1 × 10−1 min. The photodegradation of PG by the MMG catalyst was found to be significantly faster than that by individual MSG or Mn2O3. The synergistic effect of MoS2 and graphene and a higher charge separation in the composite are major factors for a higher photocatalytic activity of the MMG catalyst. Moreover, the MMG catalyst exhibits good photostability, which ensures its potential applications in wastewater treatment and other energy applications. Finally, the photocatalytic mechanism of the MMG hybrid under visible light is presented after performing some radical scavenger tests. [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]

As a member of the ternary sulfides, CdIn2S4 is a visible light responded catalyst with a band gap of 2.2–2.6 eV, which is suitable for solar spectrum. In this study, a simple two-step solvothermal method was used to construct Ni12P5/In(OH)3/CdIn2S4 composite catalysts with type-II and Z-scheme heterojunctions, and there was a synergy between the two heterojunctions. The Ni12P5/In(OH)3/CdIn2S4 composite catalyst formed a donor-mediator-acceptor system for photogenerated electrons, which greatly improved the separation efficiency of the photogenerated carriers. Moreover, the highest hydrogen production activity achieved by the Ni12P5/In(OH)3/CdIn2S4 composites was 5.75 mmol g−1 h−1, which was 21 times the original CdIn2S4. [ABSTRACT FROM AUTHOR]

A novel Cu-doped one dimensional (1D) Bi2S3 rod-shaped nanocapsule/rGO composite is explored as a photocatalyst for selective reduction of CO2 to methanol. In particular, the effects of Cu doping of rGO supported Bi2S3 on band gap tuning and on product selectivity are investigated. Bi2S3 rod-shaped nanocapsules and 0.5, 1, and 2 weight percent Cu-doped Bi2S3/rGO are synthesised through a hydrothermal approach. The photocatalysts are characterized by XRD, FTIR, UV-Vis spectroscopy, photoluminescence spectroscopy, X-ray photoelectron spectroscopy, and SEM, TEM and EDX analysis. It is revealed that Cu-doped Bi2S3/rGO for all different compositions offers selective and enhanced production of methanol compared to undoped Bi2S3/rGO, pristine Bi2S3, and Cu-doped Bi2S3 which produce formic acid along with methanol. The optimum 1 weight percent Cu-doped Bi2S3/rGO photocatalyst, exhibiting the smallest band gap and the lowest rate of recombination of electron–hole pairs, offers the highest photocatalytic activity of 719 μmol gcat.−1 h−1. DFT studies corroborate the experimental finding of a drastic reduction of the band gap (1.36 eV) of Cu-doped Bi2S3/graphene and unveil that Cu 3d–C 2p hybridization as well as enhancement of Bi 6p–C 2p hybridization in the presence of copper significantly increases the overall DOS of the system at the Fermi level, resulting in enhancement of electronic conductivity and charge transfer; further deformation in the graphene sheets due to the presence of Cu-Bi2S3 creates CO2 trapping sites for its efficient adsorption and selective photoreduction. [ABSTRACT FROM AUTHOR]

The design of organic photocatalysts with visible-light-response is an important way to solve energy crisis and environmental pollution. Polypyrrole (PPy) as one of the conjugated polymers is a prospective photocatalyst material due to its excellent optical properties, easy synthesis and high environmental stability. In this work, polyacrylonitrile (PAN) and g-C3N4 were electrospun as a fiber membrane matrix. PPy was coated on the matrix by in situ polymerization of a pyrrole monomer using doped Fe3+ as an oxidant. PPy exhibited a broadband visible light absorption region and a narrow band gap which was conducive to improve visible light utilization. The separation efficiency of photogenerated e−–h+ pairs was improved by constructing a heterojunction between PPy and g-C3N4. The doping of Fe3+ as an electron scavenger further prevented the recombination of carriers. The PAN/g-C3N4-PPy-Fe3+ membrane showed highly efficient removal performance for both cationic and anionic dyes. Moreover, PAN/g-C3N4-PPy-Fe3+ exhibited excellent recyclability and stability. This work outlined an approach for designing a novel conjugated polymer based multi-component composite photocatalyst with visible light response. [ABSTRACT FROM AUTHOR]

A new mononuclear Fe3+ metalloligand MC1 [FeLN3(H2O)], developed by using the N2O2 donor Schiff base ligand H2L, has been successfully used to detect and remove Hg2+ and Cd2+ from several transition metal ions with the formation of two unusual hetero metallic μ-oxo Fe3+–Hg2+/Cd2+ clusters, [(Fe23+)(μ-O)L2Cl4(Hg22+)] (MC2) and [(Fe23+)(μ-O)L2I4Cd22+] (MC3) [(where H2L is 6, 6′-(1E, 1′E) (ethane-1, 2 diylbis(azaneylidene))bis(methaneylylidene))bis(2-ethoxyphenol)]. All three complexes were identified by X-ray single-crystal data analysis along with a range of spectral studies. In MC1, the Fe3+ is coordinated with deprotonated H2L, one water molecule, and one azide ion as a secondary anionic residue, forming an octahedral geometry. Interestingly, MC2 and MC3 are isostructural, where each asymmetric unit contains deprotonated H2L, one Fe3+ and Hg2+/Cd2+ metal center, two Cl−/I− and two Fe3+ centers are connected by a μ-O bridge to form tetranuclear complexes. As the band gap energy values of MC1, MC2, and MC3 (3.07 eV, 2.69 eV, and 2.55 eV, respectively) are in the visible region so all the three complexes are exposed to investigate their potentiality to be effective Schottky devices and at the same time a thorough inspection has been carried out to check their catalytic behaviour in aqueous medium in terms of methylene blue (MEB) dye degradation under visible light irradiation. A thorough inspection reveals the better MB dye degradation potentiality of MC3 in comparison to MC2 in the presence of H2O2. At the same time, the investigation of the device performances, conductivity, and device parameters disclose more effectiveness of MC3 in comparison to MC2 in a better Schottky device. The effectiveness of MC3 in both applications may be attributed to its lower band gap value. [ABSTRACT FROM AUTHOR]

A multifunctional α-MnO2/ZnO--C (MZ) Z-scheme photocatalyst was synthesized by the suit-growth of α-MnO2 on the surface of MOF-5 and pyrolysis of the organic components under certain conditions. The obtained photocatalysts were characterized and the photocatalytic activity was investigated by degrading tetracycline (TC). Especially, the composite with a 15% mass ratio of α-MnO2 (15-MZ) exhibited the best photocatalytic activity for tetracycline under visible light irradiation and the degradation efficiency for TC reached 96.69% within 60 min. The doping of the C element in the ZnO crystal structure formed an intermediate energy level to narrow the band gap of ZnO, which was beneficial for visible light absorption. Also, the construction of a binary synergistic system between ZnO and α-MnO2 resulted in the extension of the light response range and accelerated the transfer of photogenerated carriers. The tests showed that h+, ¹O2, •O2-, and •OH were the main active species and played leading roles in the degradation process. Additionally, the residual C species as an electron-transfer medium were conducive to constructing the Z-scheme heterojunction between ZnO--C and α-MnO2, which provides an interesting approach for designing visible light responsive photocatalysts. [ABSTRACT FROM AUTHOR]

The substitution of C for N in graphitic carbon nitride (g-C3N4) can promote π-electron availability and increase photocatalytic activity, but the low specific surface area still limits its performance. Herein, porous C-doped g-C3N4 was prepared by the uracil-mediated supramolecular assembly of melamine and cyanuric acid. The as-prepared catalyst exhibited a high photocatalytic hydrogen evolution rate of 2352 μmol g−1 h−1 under visible light irradiation (λ ≥ 420 nm), which was 28 times that of g-C3N4 (83 μmol g−1 h−1), due to the porous architecture and C-doping effect. The porous architecture endowed the catalyst with a large specific surface area (79.4 m2 g−1) and great light utilization efficiency in the visible light region between 500 and 750 nm. In addition, C-doping modified the energy band structure of g-C3N4 to a narrow band gap (from 2.92 eV to 2.78 eV) and enhanced the separation efficiency of photogenerated carriers. [ABSTRACT FROM AUTHOR]

Photocatalytic water splitting using sunlight is one of the most promising approaches to produce hydrogen, for which increasing focus has been directed towards band gap engineering of the existing photocatalysts, like SrTiO3. A detailed theoretical study has been carried out to explain the variation of photoactivity of Ir-doped SrTiO3 with the different oxidation state (+3 and +4) of Ir. The present study reveals that localized mid gap acceptor states are the main limiting factor for the +4 state, which is absent in the case of the +3 state. Furthermore, we have investigated the effect of codoping with B, Al, La, and Cr into Ir-doped SrTiO3, which releases an extra electron to stabilise the +3 state, and at the same time to form a charge compensated system. To get knowledge about the relative feasibility of formation of various doped systems defect formation energies have been calculated. Finally, the ability to produce hydrogen has been verified by band edge alignment with respect to water redox levels. The present study reveals that although all these four codopant elements ensure the +3 state of Ir, they play differently in enhancing the photoactivity of Ir-doped SrTiO3. Considering various aspects, it has been predicted that codoping of La into Ir-doped SrTiO3 can significantly enhance the photocatalytic activity under visible light. [ABSTRACT FROM AUTHOR]

A new porphyrinic vanadium-based metal–organic framework (MOF), namely V-MOF-10 [V2(OH)2(H2TCPP)], constructed from {V(OH)O4}∞ chains and 4-tetracarboxyphenylporphyrin linkers, was synthesized by a solvothermal procedure. Structural analysis indicated that V-MOF-10 possesses orthorhombic symmetry featuring two types of pores (5.2 × 11.9 Å and 3.5 × 11.9 Å). Full characterization of V-MOF-10 was performed by powder X-ray diffraction (PXRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and elemental analysis (EA). The N2 isotherm of V-MOF-10 at 77 K shows a reversible uptake and permanent porosity with a high BET (Langmuir) surface area of 1477 m2 g−1 (1553 m2 g−1). The optical band gap of V-MOF-10, measured by UV-vis diffuse reflectance spectroscopy, is calculated to be 1.71 eV, resulting in a shift of absorption wavelength to the visible light region. Furthermore, our density functional theory (DFT) calculations confirm an acceptable correspondence of the band gap value with the mentioned experimental investigation, similar to the incorporated experimental and theoretical observations in the previous literature. Remarkably, V-MOF-10 exhibits an excellent photocatalytic property of organic dyes with the degradation efficiency of 100% for methylene blue (MB) and 89% for methylene orange (MB) after 120 min under illumination by visible light. These results suggest that V-MOF-10 could be used as a promising candidate in further photocatalytic studies. [ABSTRACT FROM AUTHOR]

A porous Cu2O/TiO2 hybrid photocatalyst with n-type Cu2O decorated on the mesoporous TiO2 derived from MIL-125 was designed through the in situ Cu2+ ion reduction strategy. Under UV-vis light irradiation, the Cu2O/TiO2 composite with 4.2 wt% of Cu2O displayed the highest hydrogen evolution rate of 14.39 mmol h−1 g−1, which was about 9.6 and 24.8 times that of the original mesoporous TiO2 and pure Cu2O, respectively. The enhancement in photocatalytic activity can be mainly attributed to the type-I band structure formed, which can efficiently enhance the photoexcited charge carrier mobility across the phase interfaces of the Cu2O/TiO2 composite, as evidenced by the UV-DRS spectra, Mott–Schottky curves, and XPS analysis. Besides, the narrow band gap of Cu2O, conducive to the absorption of visible light, and the high specific surface of TiO2 were also found to contribute to the photoactivity enhancement. This work will provide a new perspective for the study of type-I photocatalysts. [ABSTRACT FROM AUTHOR]