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Metal chalcogenides are regarded as favorable H 2 -evolution photocatalysts, however, reasonably constructing and synthesizing metal sulphides catalysts with high activity, stability, and cost-effectiveness still faces great challenges. Herein, a novel P-doped hexagonal NiS 2 /ZnS photocatalyst (P–Ni–ZnS) is facilely obtained using a one-step hydrothermal method. Its photocatalytic hydrogen evolution performance is prominently better than those of pure ZnS, P- M -ZnS (M = Cu, Co, and Mn) synthesized under the same conditions and most reported ZnS-based photocatalysts. The optimized P–Ni–ZnS-2 has the highest H 2 production rate of 26.24 mmol g−1 h−1, approximately 3, 2 and 1.5 times higher than ZnS, P–ZnS and NiS 2 /ZnS (Ni–ZnS), highlighting that the synergistic effect of P-doping and NiS 2 cocatalyst results in excellent catalytic efficiency of P–Ni–ZnS-2. Further mechanism studies have shown that P doping and NiS 2 cocatalyst significantly enhance the light capture capability, separation and migration rate of photoinduced carriers. Our work provides a simple and effective method for preparing efficient and stable metal sulfur-based photocatalysts. • One step hydrothermal synthesis of P-doped hexagonal NiS 2 /ZnS composite. • P doping and NiS 2 cocatalyst enhance the photocatalytic activity of hexagonal ZnS. • The optimized P–Ni–ZnS-2 exhibits superior HER photocatalytic activity. [ABSTRACT FROM AUTHOR]

[Display omitted] Biocompatible photocatalytic water-splitting systems are promising for tissue self-oxygenation. Herein, a structure–function dual biomimetic fingerprint-like silver phosphate/polydopamine/graphitic carbon nitride (Ag 3 PO 4 /PDA/g-C 3 N 4) heterojunction nanocomposite is proposed for enhanced solar-driven oxygen (O 2) evolution in vivo in situ. Briefly, a porous nitrogen-defected g-C 3 N 4 nanovoile (CN) is synthesized as the base. Dopamine molecules are controllably inserted into the CN interlayer, forming PDA spacers (4.28 nm) through self-polymerization-induced supramolecular-assembly. Ag 3 PO 4 nanoparticles are then in situ deposited to create Ag 3 PO 4 /PDA/CN. The fingerprint-like structure of PDA/CN enlarges the layer spacing, thereby accelerating mass transfer and increasing reaction sites. The PDA spacer roles as excellent light harvester, electronic-ionic conductor, and redox pair through conformational changes, resulting in tailored electronic band structure, optimized carrier behavior, and reduced electrochemical impedance. In physiological conditions, Ag 3 PO 4 /PDA/CN exhibits O 2 evolution rate of 45.35 μmol⋅g−1⋅h−1, 9-fold of bulk g-C 3 N 4. The biocompatibility and in vivo oxygen supply effectiveness for biomedical applications have been verified in animal models. [ABSTRACT FROM AUTHOR]

Semiconductor photocatalysis, as a safe and environmentally friendly technology, has drawn a lot of attention due to its potential to address issues with energy and the environment. Recently, different semiconductors have been designed and modified in order to obtain efficient photocatalysts. Here, semiconductor photocatalytic materials and the reaction fundamentals of semiconductor photocatalysis are briefly introduced. Six methods have been introduced to improve the photocatalytic activity of semiconductors, which are morphology and crystal modification, doping induction, plasmonic metal nanoparticles deposition, heterojunctions construction with other semiconductor materials, dye sensitization, and organic modification. Besides, the challenges and potential for developing semiconductor photocatalytic materials in the future are highlighted. It is hoped to help preparing semiconductors with better photocatalytic performance. • Outlining six methods for enhancing the performance of photocatalysts. • Discussion about the mechanism of photocatalysis. • Different methods have good photodegradation efficiency for different organic pollutants. • Introducing various methods of doping and the different types of heterojunctions. [ABSTRACT FROM AUTHOR]

Dye-induced water pollution is a noteworthy environmental issue, mainly caused by industrial activities that utilize and release effluent-containing dyes, especially azo dyes. One frequently employed large-scale technique for removing dyes from water is photocatalysis degradation. The use of MXene-based catalysts as an advanced material holds promise in overcoming the limitations inherent in previous catalysts due to its expansive surface area and unique tunable properties. The potential of integrating MXene-based catalysts with nanoparticles and semiconductors offers a path to enhance photocatalytic efficiency, create composite materials, promote environmental sustainability, and drive innovations in water purification. Further developments in MXene, including its properties, functional groups, and active sites tailored to semiconductor compatibility, can maximize the capabilities of semiconductors. The rate of photocatalytic reactions stands to improve significantly due to MXene's high light absorption capacity and extensive nanoporous structure. Consequently, MXene-based catalysts in photocatalytic degradation hold the potential to contribute to a more sustainable environment, particularly in water treatment.

In this work, two-dimensional (2D) Zn-HMT (Zn(NO3)2(HMT)2(H2O)2]n) nanosheets were synthesized using a facile one-step chemical precipitation in the presence of Zn(NO3)2, hexamine (HMT), and anhydrous ethanol at room temperature. Subsequently, hexagonal Tx-ZnO (Tx-ZnO refers to the zinc oxide (ZnO) nanoparticles) were synthesized by a high-temperature solid-phase method at different temperatures (x = 500, 550, 600, 650, 700, 750, and 800 °C) nanoparticles with different morphologies were synthesized by a high-temperature calcination approach using 2D Zn-HMT nanosheets as precursor. The crystal structure, morphology, specific surface areas, surface and interface properties, optical properties, and charge migration behaviors of the as-synthesized Tx-ZnO nanoparticles were characterized by powder X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), automatic specific surface and aperture analyzer, X-ray photoelectron spectroscopy (XPS), UV-visible spectrophotometer, photoluminescence (PL) spectra, and electrochemical impedance spectroscopy (EIS). The photocatalytic performances and stabilities of the as-synthesized typical Tx-ZnO nanoparticles with various morphologies were evaluated and compared with the commercial ZnO (CM-ZnO) nanoparticle. The T700-ZnO nanoparticle with spherical and irregular morphology exhibited the highest photocatalytic activity (99.12%) for the degradation of Rhodamine B (RhB), compared to T500-ZnO (92.32%), T600-ZnO (90.65%), T800-ZnO (44.04%), and the CM-ZnO (88.38%) nanoparticle, which can be attributed to the cooperative effects of higher crystallinity, bigger crystal size, the strongest separation efficiency, the lowest recombination rate, the fastest charge carrier transfer path, and the highest charge-transfer efficiency. The superior photocatalytic activity illustrated by the T700-ZnO nanoparticle makes it have potential application prospects for the treatment of organic wastewater. [ABSTRACT FROM AUTHOR]

The production of hydrogen from water is one of the best sustainable energy resources to fulfill the increasing energy deficiency of the world. As most of the available energy resources are harmful in one way or another as nuclear waste is dangerous for human life and burning fossil fuels caused the production of carbon, nitrogen, and Sulphur oxides which increases global warming as well as air pollution. The earth is almost 70% consist of water so that there is need to use this water in efficient way to produce hydrogen as it is more sustainable energy resource and environment friendly. This is an emerging field for researchers and they trying to find the best photocatalyst for hydrogen production. The motivation of this study is to provide improved mechanism for hydrogen production because the developing countries like Pakistan faced serious energy crisis and available energy resources in these countries are the fossil fuels mostly which are not environmentally friendly creating chaos of global warming. The background of this study shows that researcher used doped, composite, and many other different techniques to enhance its efficiency. For the last decade, researchers mainly focused on the doped photocatalyst. In recent decade researcher shifted to composite based photocatalysts. The hypothetical question arises in this study weather these composite useful to improve efficiency of hydrogen production by using photocatalyst method? This review paper especially focuses on different composite photocatalysts for hydrogen production. The composites of Cadmium Sulfite/Titanium dioxide (CdS/TiO2) and Tungsten trioxide/graphite Carbon nitride (WO3/ g-C3N4) have been the main area of interest in this review due to their immense use in research to produce hydrogen. This study will also help to understand the mechanism of the production of hydrogen through water splitting and organic compounds. The study also elaborates on the zigzag (Z) and step (S) schemes used for the photocatalytic activity of composites. Present work showed that composite photocatalyst are better and increased efficiency of hydrogen production because active sites of surface increased. This review will be helpful for new apprentices in this field to understand the basic mechanism, helpful for industrialists and experts to decide which composite photocatalyst is best according to their interests.

Introducing HAT mediator boosted the oxidation activity of toluene to benzaldehyde on the Pd loaded BiVO 4 photocatalyst under blue-to-green light irradiation, along with good selectivity. [Display omitted] • N -hydroxy compounds were applied to toluene oxidation using Pd-loaded BiVO 4 photocatalyst. • Introduction of N -hydroxyphthalimide boosted the activity up to ca. 28 times. • Excellent efficiency (apparent quantum yield = 10.8% at 420 nm and 5.4% at 520 nm) was realized. • The use of nanoparticulate Pd-loaded BiVO 4 was also effective to improve the photocatalytic activity. • Addition of N -hydroxyphthalimide also resulted in good selectivity (>99 %) of benzaldehyde production. Selective organic conversion using semiconductor photocatalysts has been focused on the viewpoint of sustainable synthesis processes. Especially, C-H activation is one of the most attractive reactions. We recently reported photo-oxidation of toluene to benzaldehyde over visible-light responsible Pd-loaded BiVO 4 (Pd/BiVO 4) photocatalyst. However, it remains challenging due to its low efficiency. Herein, we introduce a novel strategy to apply a cyclic nitroxide compound as an efficient redox mediator along with Pd/BiVO 4 for toluene oxidation. Including N -hydroxyphthalimide (NHPI) could significantly expedite the activity of benzaldehyde production up to ca. 28 times compared to without NHPI under blue-to-green light irradiation. The sustainable conditions realized a conversion in high efficiency (apparent quantum yield = 10.8 and 5.4 %@420 and 520 nm, respectively) and with excellent selectivity (>99 %). The excellent efficiency was realized by the synergistic effect between the presence of NHPI and the use of nanoparticulate Pd/BiVO 4 with a relatively large surface area. [ABSTRACT FROM AUTHOR]

Investigating efficient and selective photocatalysts for water treatment can help address the energy crisis and numerous environmental issues associated with the use of current fossil fuels. As a shell, we used nickel-layered double hydroxide nanosheets on top of an anatase TiO2-carbon core to create an integrated photocatalyst. Materials were characterized using FTIR, XRD, SEM, HRTEM, and XPS methods for their physical-chemical properties. Using N2 adsorption/desorption at −196 °C, BET-surface area and pore structure were determined. Diffuse reflectance UV–vis was used to determine the photocatalysts band gap. For the TiO2-C/NiLDH amalgam, showed the lowest band gap (3.1 eV) with an exceptional ability to degrade methyl orange as an organic pollutant. Core–shell symmetry in the TiO2-C/NiLDH amalgam provides a larger surface area (72 m2/g) for interfacial interaction and a wider base for efficient charge transfer. In subsequent tests, this photocatalyst showed a remarkable level of stability and water treatment efficacy. That the TiO2-C/NiLDH amalgam can be used to alter solar energy and protect the environment has been demonstrated by these promising results. [ABSTRACT FROM AUTHOR]

The research progress of visible light responsive BiOCl in recent years are reviewed.Illustrated the efforts of researchers to solve the problem that BiOCl can only response to ultraviolet light that the utilization rate of light was low. Summarized preparation process of semiconductor recombination, oxygen vacancy defect modification metal and non-metal doping modification and polymer sensitization BiOCl. Analyzed the main principles of various modification methods to broaden the visible light response range of BiOCl, enhance the life of photoelectron-hole pair, and improve the specific surface characteristics. The photocatalytic rate under visible light of the modified BiOCl in the application of degradation of dye wastewater, photodegradation of aquatic hydrogen, and treatment of toxic organic compounds were described.The trend and prospect of further research on BiOCl are also prospected. [ABSTRACT FROM AUTHOR]

In this work, two-dimensional (2D) Zn-HMT (Zn(NO3)2(HMT)2(H2O)2]n) nanosheets were synthesized using a facile one-step chemical precipitation in the presence of Zn(NO3)2, hexamine (HMT), and anhydrous ethanol at room temperature. Subsequently, hexagonal Tx-ZnO (Tx-ZnO refers to the zinc oxide (ZnO) nanoparticles) were synthesized by a high-temperature solid-phase method at different temperatures (x = 500, 550, 600, 650, 700, 750, and 800 °C) nanoparticles with different morphologies were synthesized by a high-temperature calcination approach using 2D Zn-HMT nanosheets as precursor. The crystal structure, morphology, specific surface areas, surface and interface properties, optical properties, and charge migration behaviors of the as-synthesized Tx-ZnO nanoparticles were characterized by powder X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), automatic specific surface and aperture analyzer, X-ray photoelectron spectroscopy (XPS), UV-visible spectrophotometer, photoluminescence (PL) spectra, and electrochemical impedance spectroscopy (EIS). The photocatalytic performances and stabilities of the as-synthesized typical Tx-ZnO nanoparticles with various morphologies were evaluated and compared with the commercial ZnO (CM-ZnO) nanoparticle. The T700-ZnO nanoparticle with spherical and irregular morphology exhibited the highest photocatalytic activity (99.12%) for the degradation of Rhodamine B (RhB), compared to T500-ZnO (92.32%), T600-ZnO (90.65%), T800-ZnO (44.04%), and the CM-ZnO (88.38%) nanoparticle, which can be attributed to the cooperative effects of higher crystallinity, bigger crystal size, the strongest separation efficiency, the lowest recombination rate, the fastest charge carrier transfer path, and the highest charge-transfer efficiency. The superior photocatalytic activity illustrated by the T700-ZnO nanoparticle makes it have potential application prospects for the treatment of organic wastewater.

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Wastewater produced by the textile industry contains various dyes and organic compounds that directly or indirectly affect surface water or groundwater pollution. Visible-light-driven semiconductor photocatalysis is the leading pathway for the degradation of environmental pollutants. Herein we report the bottom-up hydrothermal growth of 2D tin disulfide nanostructures (SnS2 NSs) for the efficient photodegradation of organic pollutants such as Rhodamine B (Rh.B) and Methyl Violet (M.V) in an aqueous medium under visible light (λ > 400 nm) irradiation. The as-synthesized SnS2 NSs were characterized by various structural, morphological, and optical techniques such as XRD, RAMAN, TEM, UV–Vis, Brunauer–Emmett–Teller, etc. Furthermore, the low bandgap (∼1.6 eV), the high surface area (56 m2/g), and the anionic nature of SnS2 NSs attribute to it as an efficient photocatalyst for photocatalytic applications. The photocatalytic properties of SnS2 NSs showed good degradation efficiency of 94 and 99.6% for Rh. B and M.V, respectively, in 25 min. The kinetic rate constant of these dyes was estimated by using the Langmuir–Hinshelwood model. Here we also performed the recyclability test of the photocatalyst and discussed the plausible mechanism for the photocatalytic degradation of organic pollutants. The XPS spectra of SnS2 NSs were studied before and after the photodegradation of Rh.B and M.V, indicating the high stability of the photocatalyst. Moreover, in vitro cytotoxicity was also evaluated against human cervical cancer cell lines (HeLa cells) with different concentrations (0–1,000 μg/ml) of as-synthesized SnS2 NSs. This intended work provides a possible treatment for the degradation of organic pollutants under visible light to balance the aquatic ecosystems.

S-schematic CuWO 4 /ZnO nanocomposite photocatalyst was synthesized by an impregnation method. Synthesized CuWO 4 and ZnO nanoparticles, and CuWO 4 /ZnO nanocomposites were thoroughly characterized. X-ray diffraction (XRD) analysis of the CuWO 4 /ZnO nanocomposite confirmed the respective triclinic and hexagonal wurtzite structures of CuWO 4 and ZnO crystals. Raman and Fourier transform infrared (FTIR) spectra and X-ray photoelectron spectroscopy (XPS) revealed bond formations in CuWO 4 and ZnO, and confirmed the synthesis of the CuWO 4 /ZnO nanocomposite. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed CuWO 4 nanoparticles adhered to ZnO aggregates. Energy dispersive X-ray spectrometry (EDS) confirmed the distribution of CuWO 4 on the ZnO aggregates. UV–Vis diffuse reflectance spectroscopy (DRS) showed optical bandgap energies of 2.36 eV for CuWO 4 and 3.18 eV for ZnO nanoparticles. The photocatalytic performance of the CuWO 4 /ZnO nanocomposite was investigated through the degradation of the cationic dyes methylene blue (MB) and Rhodamine B (RhB) and the anionic dye methyl orange (MO). A 5.0%CuWO 4 /ZnO nanocomposite degraded 100% of MB within 120 min, 91.02% of RhB within 300 min, and 89.13% of MO within 300 min. The pseudo-first order kinetic rate constant fit well for the degradation of all the dyes on the CuWO 4 /ZnO nanocomposite. The CuWO 4 /ZnO nanocomposite could better degrade the cationic dyes than the anionic dye in an aqueous solution. The hole (h+), the hydroxyl radical (•OH), and the superoxide ion (• O 2 −) were the active species responsible for degrading MB, RhB and MO dyes. The proposed CuWO 4 /ZnO nanocomposite could be applied for environment friendly wastewater treatment. [Display omitted] • CuWO 4 /ZnO nanocomposites were synthesized by an impregnation method. • 5.0%CuWO 4 /ZnO nanocomposite showed the best photocatalytic degradation. • Photogenerated electron-hole pair recombination decreased due to S-schematic charge transfer. • 5.0%CuWO 4 /ZnO nanocomposite degraded 100% of MB, 91.02% of RhB and 89.13% of MO. • h+,.•OH and • O 2 − were active species responsible for photocatalytic degradation. [ABSTRACT FROM AUTHOR]

Generating controllable N-oxyl radicals is an efficient method for the C–H bonds activation. Here the promotion effect of N-hydroxyphthalimide (NHPI) on the photocatalytic C(sp3)–H bond activation over various metal oxides was systemically studied with control experiments, UV-Vis DRS, FT-IR, ESR, and PCR. Two photocatalytic mechanisms were highlighted for the generation of critical PINO radical from NHPI: (1) The hole oxidation mechanism, the photo-induced hole (h+) of metal oxides directly oxidize the adsorbed NHPI* to a confined PINO*; (2) Ligand-to-metal charge transfer (LMCT) mechanism, the light induces the electron transfer from adsorbed NHPI* to oxides with a wide-band gap and provides a confined PINO*. Furthermore, this work also highlights a lattice-molecular structure matching effect to explain the success of certain oxides in building the h+ oxidation or LMCT systems with NHPI. The corresponding results can inspire further photocatalysis of semiconductors in C–H bond activation with versatile N-oxyl radicals. [Display omitted] • The photocatalytic C(sp3)–H bond activation over various NHPI/metal oxide systems was systemically studied. • The hole oxidation and ligand-to-metal charge transfer mechanisms were highlighted to describe the PINO radical generation. • A lattice-molecular structure matching effect was proposed to explain the success of certain metal oxides/NHPI systems. • The kinetic characterization of the confined N-oxyl radical over the typical NHPI/α-Fe 2 O 3 system was studied. [ABSTRACT FROM AUTHOR]

• SCN/Ag/AgI and AgI photocatalysts were fabricated via co-precipitation method. • MB removal efficacy was 88% using SCN/Ag/AgI nanocomposite. • SCN/Ag/AgI nanocomposite followed direct Z-scheme charge transfer route. • Ag as e- mediator facilitated charge separation by reducing inner self-recombination. • •OH and •O 2 – radicals reactive species that effectively degraded MB molecules. In this work, we scrutinized the photodegradation ability of a novel composite material, sulfur-doped graphitic carbon nitride/Ag/AgI (SCN/Ag/AgI) for methylene blue (MB) dye degradation. The SCN/Ag/AgI nanocomposite was fabricated by a cost-effective co-precipitation method. The fabricated SCN/Ag/AgI nanocomposite exhibited significantly enhanced photocatalytic activity i.e. 88% MB degradation rate. The SCN/Ag/AgI heterojunction followed a direct Z-scheme charge transferal channel in which Ag worked as an electron mediator. Furthermore, •OH and •O 2 – radicals reactive species were formed that efficiently destroyed MB pollutants. [ABSTRACT FROM AUTHOR]

Photocatalytic overall water splitting into hydrogen and oxygen on RuO2-loaded Sm3+-doped CeO2 was examined. Pure CeO2 showed a negligible small activity, however Sm3+ doped CeO2 with heterogeneous doping structure synthesized by solid state reaction exhibited an efficient activity, whereas Sm3+- doped CeO2 with homogeneous doping structure showed little activity when prepared by co-precipitation method. In this study, the relation between photocatalytic activity and surface doping structure was investigated. [ABSTRACT FROM AUTHOR]

Ag3PO4/g-C3N4 heterojunctions, with different g-C3N4 dosages, were synthesized using an in situ deposition method, and the photocatalytic performance of g-C3N4/Ag3PO4 heterojunctions was studied under simulated sunlight conditions. The results revealed that Ag3PO4/g-C3N4 exhibited excellent photocatalytic degradation activity for rhodamine B (Rh B) and phenol under the same light conditions. When the dosage of g-C3N4 was 30%, the degradation rate of Rh B at 9 min and phenol at 30 min was found to be 99.4% and 97.3%, respectively. After five cycles of the degradation experiment for Rh B, g-C3N4/Ag3PO4 still demonstrated stable photodegradation characteristics. The significant improvement in the photocatalytic activity and stability of g-C3N4/Ag3PO4 was attributed to the rapid charge separation between g-C3N4 and Ag3PO4 during the Z-scheme charge transfer and recombination process.

Graphical abstract Highlights • Novel 2D-ternary photocatalysts of NiFe-LDH and rGO co-loaded with ultrathin LTO were synthesized. • 2D-ternary photocatalyst showed a remarkable photocatalytic H2 activity under simulated light without the need of Pt. • Synergetic coupling between NiFe-LDH and rGO enhance the charge separation/ transportation and water splitting performance. • The enhanced photocatalytic mechanism was proposed. Abstract Developing photocatalysts with effective charge separation and fast surface reaction kinetics is crucial to realizing efficient photocatalytic water splitting. In this study, we report a strongly coupled two-dimensional-ternary-heterostructured photocatalyst by sequentially introducing reduced graphene oxide (rGO) and NiFe-layered double hydroxide (NiFe-LDH) on the surface of lanthanum titanate (LTO) via a facile hydrothermal and electrostatic self-assembly methodology, respectively. The synthesized 2D-rGO/LTO/NiFe-LDH photocatalyst showed remarkable photocatalytic H 2 evolution activity under simulated light irradiation, even without expensive Pt cocatalyst. The enhancement of photocatalytic activity could be attributed to the efficient interfacial charge transfer at the rGO/LTO heterojunction interface, and the enhanced hole (h+) trapping ability of NiFe-LDH cocatalyst at the LTO/NiFe-LDH interface, respectively. These attributes could effectively enlarge the life time of photo-generated electron-hole pairs, and increase the electron density for hydrogen production. The optimal rGO/LTO/NiFe-LDH nanocomposite remain sustained even after four successive experimental runs, without apparent change in the H 2 evolution rate. The present work elucidates a new strategy to maximize the efficiency via synergetic effect of incorporating rGO and NiFe-LDH as dual cocatalysts, and shows a feasible strategy of using earth-abundant materials as cocatalysts to enhance the overall photocatalytic water splitting reactions. [ABSTRACT FROM AUTHOR]

The production of hydrogen from water is one of the best sustainable energy resources to fulfill the increasing energy deficiency of the world. As most of the available energy resources are harmful in one way or another as nuclear waste is dangerous for human life and burning fossil fuels caused the production of carbon, nitrogen, and Sulphur oxides which increases global warming as well as air pollution. The earth is almost 70% consist of water so that there is need to use this water in efficient way to produce hydrogen as it is more sustainable energy resource and environment friendly. This is an emerging field for researchers and they trying to find the best photocatalyst for hydrogen production. The motivation of this study is to provide improved mechanism for hydrogen production because the developing countries like Pakistan faced serious energy crisis and available energy resources in these countries are the fossil fuels mostly which are not environmentally friendly creating chaos of global warming. The background of this study shows that researcher used doped, composite, and many other different techniques to enhance its efficiency. For the last decade, researchers mainly focused on the doped photocatalyst. In recent decade researcher shifted to composite based photocatalysts. The hypothetical question arises in this study weather these composite useful to improve efficiency of hydrogen production by using photocatalyst method? This review paper especially focuses on different composite photocatalysts for hydrogen production. The composites of Cadmium Sulfite/Titanium dioxide (CdS/TiO 2) and Tungsten trioxide/graphite Carbon nitride (WO 3 / g-C 3 N 4) have been the main area of interest in this review due to their immense use in research to produce hydrogen. This study will also help to understand the mechanism of the production of hydrogen through water splitting and organic compounds. The study also elaborates on the zigzag (Z) and step (S) schemes used for the photocatalytic activity of composites. Present work showed that composite photocatalyst are better and increased efficiency of hydrogen production because active sites of surface increased. This review will be helpful for new apprentices in this field to understand the basic mechanism, helpful for industrialists and experts to decide which composite photocatalyst is best according to their interests. [ABSTRACT FROM AUTHOR]

Two-dimensional thin Bi2WO6 nanoplates have been fabricated using a cetyltrimethylammonium bromide (CTAB)-assisted hydrothermal method. We investigated the proposed formation mechanism based on the crystalline structures of the thin Bi2WO6 nanoplates. The high adsorption ability and excellent visible-light driven photocatalytic activities of the Bi2WO6 nanoplates were illustrated, in view of exposed (001) facets of nanoplates possessing faster separation of photo-generated charge carriers and increased catalytically active sites. Such a cost-effective way to obtain Bi2WO6 nanoplates offers new possibilities for the design of adsorptive semiconductor photocatalysts with strengthened photocatalytic activities. [ABSTRACT FROM AUTHOR]

The abundant energy provided by sunlight makes visible-light driven photoredox catalysis an attractive means of performing chemical transformations. Titanium dioxide (TiO 2 ) and conjugated polymers are semiconducting materials that have been used as photoredox catalysts. Driving electron transfer process with photoredox catalysts and visible light has become a powerful method for achieving efficient chemical transformations. However, titanium dioxide does not readily absorb visible light, and conjugated polymers have not been extensively studied as photoredox catalysts for organic transformations. In this work, TiO 2 and the conjugated polymer poly- p -phenylene (PPP) were successfully used as heterogeneous co-catalysts for the dehalogenation of some simple aryl halides using triethylamine as a sacrificial electron donor. While PPP alone exhibited some photocatalytic activity upon irradiation with visible light, the efficiency of dehalogenation was enhanced by the addition of titanium dioxide. No reaction was observed in the absence of both photocatalysts or when TiO 2 was used as the sole photocatalyst. The optimum operating parameters were examined. [ABSTRACT FROM AUTHOR]

A novel all-solid-state Z-scheme visible-light-driven photocatalytic material, CuBi 2 O 4 /In 2 O 3 was successfully prepared by loading CuBi 2 O 4 onto flower-like In 2 O 3. The resulting material was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, UV-diffuse reflectance spectroscopy (UV-DRS), Brunauer–Emmett–Teller (BET) surface area, X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), Raman spectroscopy, and X-ray diffraction (XRD). Compared with single-phase CuBi 2 O 4 and In 2 O 3 , the coupled composite phase of 15% CuBi 2 O 4 /In 2 O 3 (15CuIn) showed superior photocatalytic activity. Its decolorization rate of methylene blue (MB) could reach 97% in 80 min under visible light irradiation and could be maintained at 85% after four cycles. The outstanding photocatalytic performance of CuBi 2 O 4 /In 2 O 3 was attributed to the formation of a Z-scheme heterogeneous structure, which increased the visible light absorption, enhanced the specific surface area, and improved the interfacial charge transfer efficiency. This study provides a novel approach for the construction of efficient heterojunction photocatalysts for wastewater treatment. • A novel all-solid-state visible-light photocatalyst CuBi 2 O 4 /In 2 O 3 was first successfully prepared. • The decolorization rates of MB could reach 97% in 80 min. • The Z-scheme heterogeneous structure increases visible light absorption, and improves interfacial charge transfer efficiency. [ABSTRACT FROM AUTHOR]

Highly hierarchical hollow bismuth tungstate (Bi2WO6) microspheres self-assembled by thin nanoplates have been fabricated via a facile template-free solvothermal route. The possible growth pattern and formation mechanism of hierarchical hollow Bi2WO6 microspheres was investigated. The excellent visible-light-driven photocatalytic performance on rhodamine B (RhB) degradation was displayed by hierarchical hollow Bi2WO6 microspheres. Such well-organized hierarchical hollow Bi2WO6 microspheres show potential application in water treatment fields by full use of solar energy. [ABSTRACT FROM AUTHOR]

In this work, a novel organic–inorganic heterostructured photocatalyst: porous graphitic carbon nitride (g-C 3 N 4 ) hybrid with copper sulfide (CuS) had been synthesized via a precipitation-deposition method at low temperature for the first time. UV–vis spectroscopy revealed the porous g-C 3 N 4 /CuS nanocomposites showed a strong and broad visible light absorption. Furthermore, the g-C 3 N 4 /CuS nanocomposites showed higher photocatalytic activity in the photodegradation of various organic dyes than that of pure g-C 3 N 4 and CuS, and the selected sample of g-C 3 N 4 /CuS-2 exhibited the best photocatalytic activity under visible light. The good photocatalytic activity could be ascribed to the matching of the g-C 3 N 4 and CuS band gap energies. Besides, photoluminescent spectra and photoelectrochemical measurements also proved that the CuS/g-C 3 N 4 could greatly enhance the charge generation and suppress the charge recombination of photogenerated carriers. According to the experimental result, a possible photocatalytic mechanism has been proposed. Due to the high stability, the porous g-C 3 N 4 /CuS could be applied in the field of environmental remediation. Our work highlights that coupling semiconductors with well-matched band energies provides a facile way to improve the photocatalytic activity. [ABSTRACT FROM AUTHOR]

As an advanced oxidation process, the catalytic efficiency of photocatalysis has been greatly improved because the size of catalytic materials has been reduced to nano level. However, the reduced size also makes it more difficult to reuse. In view of the fact that hydrogel composite photocatalyst can improve the practicability and economy of photocatalyst, the research and application of hydrogel composite photocatalyst deserve to be concerned. In this review, the research on hydrogel as the carrier of photocatalyst (Mainly including Titanium oxide, Carbon nitride, Metal sulfide) and the selection and preparation methods of hydrogel in recent five years is summarized. The factors affecting the photocatalytic efficiency of the composite gel system and the evaluation indexes are listed and discussed in detail. In addition, the mechanism of synergistic degradation of hydrogel composite photocatalyst was also discussed. The results showed that photocatalytic degradation and hydrogel adsorption promoted each other. Finally, the existing problems of hydrogel composite photocatalyst are summarized, and the development prospect is forecasted. [ABSTRACT FROM AUTHOR]

A facile one-pot microwave assisted solvothermal synthesis using various ratios of ethylene glycol (EG) and ethanol was developed to synthesize flower-like BiOBr microspheres. Such synthesized microspheres were characterized using X-ray photoelectron spectroscopy, X-ray diffraction, field emission scanning electron microscopy, high resolution transmission electron microscopy, the Brunauer-Emmett-Teller surface area, and UV-Visible diffuse reflectance spectra. Flower-like BiOBr microspheres were composed of loosely packed nanoplates which are interconnected to each other. Experimental results suggested that ethanol played a crucial role in directing the construction of microspheres without any misorientations. The photocatalytic activity of BiOBr microspheres was tested using the photodegradation of tartaric acid irradiated with visible light and compared with solvothermally synthesized BiOBr microspheres and commercial BiO. BiOBr microspheres synthesized using the solvent mixture containing EG and ethanol at the ratio of 3:1 could degrade 98 % tartaric acid in 240 min with visible light (λ ≥ 400 nm) due to the synergistic effect of favorable microstructure with high surface area and suitable band gap of 2.92 eV. Since the resulting BiOBr microspheres are reusable without any loss in photocatalytic activity and more stable without any change in their morphology, it holds as a very promising photocatalysts for the treatment of organic pollutants. [ABSTRACT FROM AUTHOR]

Novel HSbO 3 /graphitic carbon nitride (HSbO 3 /g-C 3 N 4 ) heterojunction photocatalysts were synthesized via a simple method. The prepared HSbO 3 /g-C 3 N 4 samples were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), ultraviolet–visible diffuse reflection spectroscopy (DRS) and photoluminescence spectroscopy (PL). The photocatalytic activity of as-synthesized samples was evaluated by degrading Rhodamine B (RhB) in aqueous solution under visible-light irradiation. All the HSbO 3 /g-C 3 N 4 heterojunction photocatalysts showed much higher visible-light photocatalytic activity than those of pure g-C 3 N 4 , HSbO 3 for the degradation of RhB. The enhanced photocatalytic activity is mainly ascribed to the enhancement of electron–hole separations at the interface of the two semiconductors. This study offers a new class of highly efficient and promising heterojunction photocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel CNTs@CuBi 2 O 4 /AgBiO 3 hydrothermally fabricated photocatalyst. • 97.94% of MB photocatalytic degradation by CNTs@CuBi 2 O 4 /AgBiO 3. • CNTs mediating the charge transfer in between CuBi 2 O 4 /AgBiO 3. • All solid state Z-scheme mechanism. A novel CNTs@CuBi 2 O 4 /AgBiO 3 , All-Solid State (ASS) Z-scheme photocatalyst was hydrothermally synthesized to explore visible light photocatalytic performance via methylene blue degradation. The ASS Z-scheme heterojunction exhibited 97.94% of degradation in 60 min in visible light. Besides, the photocatalytic activity of heterojunction remained 89.50% after 10 cycles, signifying high stability and reusability of heterojunction. The presence of CNTs on CuBi 2 O 4 /AgBiO 3 nanoparticles acted as an electron transfer bridge in-between CuBi 2 O 4 and AgBiO 3. The ASS Z-scheme-based photocatalytic mechanism considerably enhanced photo-exciton lifetime, longer stability, increased visible light absorption, and photocatalytic activity of fabricated CNTs@CuBi 2 O 4 /AgBiO 3. [ABSTRACT FROM AUTHOR]

Highly hierarchical hollow bismuth tungstate (Bi2WO6) microspheres self-assembled by thin nanoplates have been fabricated via a facile template-free solvothermal route. The possible growth pattern and formation mechanism of hierarchical hollow Bi2WO6 microspheres was investigated. The excellent visible-light-driven photocatalytic performance on rhodamine B (RhB) degradation was displayed by hierarchical hollow Bi2WO6 microspheres. Such well-organized hierarchical hollow Bi2WO6 microspheres show potential application in water treatment fields by full use of solar energy.

In this study, orthorhombic WO3 (tungsten trioxide) nanoparticles with light absorption properties in the visible region were successfully synthesized via reverse microemulsion at room temperature. The morphology, size, phase composition, structure, and optical properties of these particles were characterized. Through this method, highly crystalline and well-dispersed WO3 nanoparticles with a phase-pure were successfully obtained. The photocatalytic activities of tungsten trioxide nanoparticles were evaluated by the degradation of methylene blue (MB, used as a probe) dye under visible light irradiation, which exhibits a high photocatalytic MB dye degradation activity as compared to bulk WO3 and the commercial P-25 TiO2 powder. [ABSTRACT FROM AUTHOR]

Monodispersed Bi2O2CO3 nanoplates with an average width of 320 nm and thicknesses of 50-90 nm were successfully synthesized by a simple solvothermal method in a mixture solution of polyethylene glycol and H2O. The obtained nanoplates were characterized by means of XRD, FT-IR, SEM and TEM. The effect of surfactant sodium dodecyl benzene sulfonate on the morphology of Bi2O2CO3 product was investigated. Under simulated solar light irradiation, Bi2O2CO3 nanoplates exhibited superior photocatalytic activities towards the degradation of RhB as well as high chemical stability upon cycling photocatalytic test. The nanoplates also showed promising photodegradation ability for eliminating refractory pollutant of phenol. The excellent photocatalytic performance of Bi2O2CO3 nanoplates as compared with P25-TiO2 endows them as promising high efficiency photocatalysts. [ABSTRACT FROM AUTHOR]

Abstract: Lanthanum ferrite nanoparticles (LaFeO3 NPs) with light absorption properties in the visible region were successfully synthesized in CTAB (cetyltrimethyl ammonium bromide) emulsion nanoreactors at room temperature. The morphology, size, structure, elemental composition, and optical properties of these particles were characterized by field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), X-ray fluorescence (XRF), and ultraviolet–visible absorption (UV–Vis) spectroscopy. Through this method, highly crystalline and well-dispersed perovskite LaFeO3 NPs with a phase-pure were successfully obtained. The band gap energy (E g) of the LaFeO3 NPs was calculated by UV-Vis spectroscopy at the wavelength of about 517nm and is observed to have a value of 2.43eV. The photocatalytic activities of LaFeO3 NPs were evaluated by the degradation of toluidine blue O (TBO, used as a probe) dye under visible light irradiation, which exhibits a high photocatalytic TBO dye degradation activity as compared to the commercial P-25 titania powder. This phenomenon is due to smaller band gap energy and changing from bulk to nanostructure. The higher photocatalytic activity is also related to the photo absorption. [Copyright &y& Elsevier]

Methane is one of the promising alternatives of petroleum, which should be used for not only a fuel but also a resource for hydrogen and more useful chemicals as with the petroleum. However, the selective methane conversion to them is still difficult in contrast to the combustion. Three types of photocatalytic reactions for methane conversion, i.e., the photocatalytic non-oxidative coupling of methane (2CH → CH + H), the photocatalytic dry reforming of methane (CH + CO → 2CO + 2H) and the photocatalytic steam reforming of methane (CH + 2HO → 4H + CO), can take place around room temperature or at a mild condition such as 473 K using photoenergy and semiconductor photocatalyst. In the present short review, the details of each photocatalytic reaction and the design concept of the semiconductor photocatalysts for each photocatalytic methane conversion were summarized and discussed. [ABSTRACT FROM AUTHOR]

Abstract: Photocatalytic reduction of carbon dioxide to fuels using solar energy is an attractive option for simultaneously capturing this major greenhouse gas and solving the shortage of sustainable energy. Efforts to demonstrate the photocatalytic reduction of CO2 are reviewed herein. Although the photocatalytic results depended on the reaction conditions, such as the incident/absorbing light intensity from the sun or a simulated solar light source, the performance of different systems is compared. When the reactants included CO2 and water, it was necessary to determine whether the products were derived from CO2 and not from impurities that accumulated on/in the catalysts as a result of washing, calcination, or pretreatment in a moist environment. Isotope labeling of 13CO2 was effective for this evaluation using Fourier-transform infrared (FTIR) spectroscopy and mass spectrometry (MS). Comparisons are limited to reports in which the reaction route was verified spectroscopically, the C source was traced isotopically, or sufficient kinetic analyses were performed to verify the photocatalytic events. TiO2 photocatalytically produced methane at the rate of ∼0.1μmolh−1 gcat −1. In aqueous solutions, formic acid, formaldehyde, and methanol were also produced. When TiO2 was atomically dispersed in zeolites or ordered mesoporous SiO2 and doped with Pt, Cu, N, I, CdSe, or PbS, the methane and CO formation rates were greater, reaching 1–10μmolh−1 gcat −1. As for semiconductors other than TiO2, CdS, SiC, InNbO4, HNb3O8, Bi2WO6, promoted NaNbO3, and promoted Zn2GeO4 produced methane or methanol at rates of 1–10μmolh−1 gcat −1, and promoted AIILa4Ti4O15 produced CO at a rate greater than 10μmolh−1 gcat −1, in addition to the historically known ZnO and GaP (formaldehyde and methanol formation). The photocatalytic reduction of CO2 was also surveyed with hydrogen, because hydrogen can be obtained from water photosplitting by utilizing natural light. CO was formed at a rate of ∼1μmolh−1 gcat −1 using TiO2, ZrO2, MgO, and Ga2O3, whereas both CO and methanol were formed at a rate of 0.1–1μmolh−1 gcat −1 using layered-double hydroxides consisting of Zn, Cu, Al, and Ga. When hydrogen is used, in addition to identifying the origin of the carbon, it is critical to confirm that the products are photocatalytically formed, not thermally produced via CO2 hydrogenation. The feasibility of the strategy involving the recycling of a sacrificial electron donor and the direct supply of protons and electrons released from water oxidation catalysts to photocatalysts for the reduction of CO2 to fuels has been demonstrated. However, based on the results obtained to date, it is clear that the practical use of the photocatalytic reduction of CO2 as one possible solution for global warming and the world''s energy problems requires the development of more efficient photocatalysts. [Copyright &y& Elsevier]

Abstract: The enhanced photocatalytic activity of needle-like TiO2/WO3−x (0< x ≤0.3) composite thin films is demonstrated in the degradation of stearic acid, a model system for the organic pollutants typically present on window surfaces. The films were synthesised by atmospheric pressure chemical vapour deposition (APCVD) from reaction of tungsten and titanium chlorides with ethanol and ethyl acetate as oxygen sources, respectively, and characterised by X-ray diffraction, Raman spectroscopy, SEM and AFM. The increase in activity of films is explained in terms of an effective vectorial charge separation at the interface of the two oxide semiconductors. The interaction of water with the surface of the TiO2/WO3−x composite film is also discussed after water droplet contact angle measurements. [Copyright &y& Elsevier]

CeO2 nanoparticles were prepared by a simple precipitation method, followed by calcination treatment. By selecting photocatalytic degradation of acid orange 7 (AO7) as a probe reaction, the influences of calcination temperature of catalyst, the concentration of AO7, initial pH value of AO7 solution and catalyst dosage on the photocatalytic activity of CeO2 were studied. It was found that CeO2 calcined at 550°C shows the highest photocatalytic activity under visible light irradiation. It was revealed that under visible light irradiation the degradation of AO7 over CeO2 nanoparticles follows a dye self-sensitization mechanism. The degradation rate of AO7 increases with decrease in the initial pH value of the reaction solution, and degradation efficiency decreases with increase in the initial dye concentration. The optimal dosage of CeO2 in solution for AO7 degradation is 1 g/L. [ABSTRACT FROM PUBLISHER]

Inorganic layered crystals exemplified by clay minerals can be exfoliated in solvents to form colloidal dispersions of extremely thin inorganic layers that are called nanosheets. The obtained "nanosheet colloids" form lyotropic liquid crystals because of the highly anisotropic shape of the nanosheets. This system is a rare example of liquid crystals consisting of inorganic crystalline mesogens. Nanosheet colloids of photocatalytically active semiconducting oxides can exhibit unusual photoresponses that are not observed for organic liquid crystals. This review summarizes experimental work on the phase behavior of the nanosheet colloids as well as photochemical reactions observed in the clay and semiconducting nanosheets system. [ABSTRACT FROM AUTHOR]

Renewable energy systems are a critical game changer of the 21st century, where various fundamental and applied researches are realised for advancing the practicality of energy provision at a multitude of scales. This study aimed to unravel the roles of H+, Na+ and K+ cations over the self-photorechargeability of a novel Pt/MoO 3 photoanode-driven photoelectrochemical (PEC) system with dual-functionalities of solar photon-to-electron conversion and storage of electrons. FE-SEM analysis showed that the Pt/MoO 3 photoanode consists of a 3D plate-like surface structure with favourable void spaces and internal channels for promoting the photo-intercalation and de-intercalation reactions. HR-TEM analysis validated the formation of interfacial heterojunction between Pt co-catalyst and MoO 3 in Pt/MoO 3 photoanode for improving the overall work function as well as synergising the self-photorechargeability properties. Further current and charge density profiling for the Pt/MoO 3 -driven self photorechargeable system over three consecutive charging-discharging cycles demonstrated a slow charge decay kinetics in H+ electrolyte resulted in a relatively high charge density of 5.53 mC/cm2. EIS Nyquist analysis depicted a smaller arc radius in the Nyquist plot of the Pt/MoO 3 -driven self photorechargeable system which indicates a lower charge transfer impedance and thus, facilitating a better separation efficiency of electron-hole pairs than bare MoO 3. From the systematic study on H+, Na+ and K+ cations with varying concentrations over the self-photorechargeability of Pt/MoO 3 -driven system, it was revealed that the K+ electrolyte at a low concentration of 0.01 M resulted in the highest charge density of 22.89 mC/cm2. Other H+ and Na+ cations and concentrations are unfavourable due to the potentiality in inducing structural distortment as well unparallel rates of charging and discharging in the Pt/MoO 3 -driven system. Finally, DFT was simulated and the calculated binding energies (E ads) between the studied cations with the Pt/MoO 3 crystalline framework validated the experimental finding. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Tape casting method was used to prepare ZnO plates for photocatalytic degradation of Reactive Orange 16 (RO 16) and Reactive Red 180 (RR 180) textile dyes in aqueous solutions. The plates were sintered at 700°C and 1050°C and characterized by using TG-DTA, BET and SEM. The sintering process at 700°C yields relatively high surface area ZnO plates comparing with the plates sintered at 1050°C. The photocatalytic activity was enhanced when the high surface area plates were used in photocatalytic degradation processes. Up to 95.7% and 88.6% color removal was obtained in 90min for the RR 180 and RO 16 aqueous solutions, respectively, when the plates were sintered at 700°C. Total organic carbon (TOC) removal was 43% at 180min for RR 180 solution. Photocorrosion tendency was observed to some extend during photocatalysis when multiple tests were performed on the same plate. This corrosive effect was recovered by the memory effect when the plates were subjected to dark interval overnight. [Copyright &y& Elsevier]