Mesoporous black TiO2-x/Ag nanospheres coupled with g-C3N4 nanosheets as 3D/2D ternary heterojunctions visible light photocatalysts

Black Titanium Oxide/Activated TaS2 Flakes Photoelectrode for Plasmon Assisted Hydrogen Evolution at Neutral pH at High Current Density

A heterojunction photo-electrode(s) consisting of porous black titanium oxide (bTiO2) and electrochemically self-activated TaS2 flakes is proposed and utilized for hydrogen evolution reaction (HER). The self-activated TaS2 flakes provide abundant catalytic sites for HER and the porous bTiO2, prepared by electrochemical anodization and subsequent reduction serves as an efficient light absorber, providing electrons for HER. Additionally, Au nanostructures are introduced between bTiO2 and TaS2 to facilitate the charge transfer and plasmon-triggering ability of the structure created. After structure optimization, high HER catalytic activity at acidic pH and excellent HER activity at neutral pH are achieved at high current densities. In particular, with the utilization of bTiO2@TaS2 photoelectrode (neutral electrolyte, sunlight illumination) current densities of 250 and 500 mA cm-2 are achieved at overpotentials of 433, and 689 mV, respectively, both exceeding the "benchmark" Pt. The addition of gold nanostructures further reduces the overpotential to 360 and 543 mV at 250 and 500 mA cm-2, respectively. The stability of the prepared electrodes is investigated and found to be satisfying within 24 h of performance at high current densities. The proposed system offers an excellent potential alternative to Pt for the development of green hydrogen production on an industrial scale.

Biotemplated Fe/La-co-doped TiO2 for photocatalytic depth treatment of compressed leachate from refuse transfer station

Compressed leachate is a contaminated liquid containing various organic and inorganic pollutants produced in municipal refuse transfer stations, which pollute soil and groundwater, posing serious risks to the environment and human health. The Environmental Technology Co., Ltd. (Shenzhen, Guangdong Province, South China) treated compressed leachate obtained from a refuse transfer station. The chemical oxygen demand (COD) (641.2 mg/L) of treated compressed leachate did not meet the wastewater quality standards in China for discharge into municipal sewers (COD ≤ 500 mg/L) and the company's design discharge requirements (COD ≤ 400 mg/L). Therefore, their further in-depth treatment is necessary. To this end, waste tobacco leaves were used as the biotemplate herein, and Fe/La-co-doped TiO2 (xFe,yLa)-TTiO2(g) was synthesized using a solvothermal-assisted biotemplating method. The photocatalytic depth treatment of compressed leachate was performed under simulated solar light using the prepared catalysts. After (3Fe,3La)-TTiO2(g) treatment, the COD of the leachate decreased from 641.2 to 280.1 mg/L, and the COD removal rate was 1.2, 1.1, and 1.6 times higher than that of pure Fe-doped, La-doped and non-biological template TiO2, respectively. Characterization confirmed that the biological template endowed the catalyst with a unique morphology and high specific surface area. Its rich activity sites are conducive to enhancing the adsorption capacity of pollutants and providing an ideal place for photocatalytic reactions. Co-doping with iron and lanthanum ions altered the band structure of TiO2 and promoted the interconversion of Fe3+/Fe2+ and La3+/La2+ during photocatalysis. First-principles density functional theory simulations demonstrated that co-doping Fe and La in TiO2 created impurity levels that facilitated the transfer of photogenerated electrons. This study provides a new purification pathway for the depth treatment of compressed leachate.

Black TiO2 Photoanodes for Direct Methanol Photo Fuel Cells

Photocatalytic fuel cells (PFCs) are considered the next generation of energy converter devices, since they can harvest solar energy through relatively low-cost semiconductor material to convert the chemical energy of renewable fuels and oxidants directly into electricity. Here, we report black TiO2 nanoparticle (NP) photoanodes for simple single-compartment PFCs and microfluidic photo fuel cells (μPFCs) fed by methanol. We show that Ti3+ and oxygen vacancy (OV) defects at the TiO2 NPs are easily controlled by annealing in a NaBH4-containing atmosphere. This optimized noble-metal-free black TiO2 photoanode shows superior PFC performance for methanol oxidation and O2 reduction with a maximum power density (Pmax) ∼2000% higher compared to the undoped TiO2. At flow conditions, the black TiO2 photoanode showed a Pmax ∼90 times higher than the μFC equipped with regular TiO2 in the dark. The PFC and μPFC operate spontaneously with little activation polarization, and black TiO2 photoanodes are stable under light irradiation. The improved photoactivity of the black TiO2 photoanode is a consequence of the self-doping with Ti3+/OV defects, which significantly red-shifted the bandgap energy, induced intragap electronic states, and widened both the valence band and conduction band, enhancing the overall absorption of visible light and decreasing the interfacial charge transfer resistance.

Oxygen vacancy engineering of TiO2 nanosheets for enhanced photothermal therapy against cervical cancer in the second near-infrared window

Cervical cancer is the most common and deadly female cancer on the worldwide scale. Considering that the conventional surgery treatment and chemotherapy would cause certain side effects, photothermal therapy (PTT) possesses desired therapeutic efficiency and insignificant side effects against cervical cancer. However, the lack of efficient and safe photothermal agents that operate in the second near-infrared (NIR-II) window is a main obstacle hindering the clinical transformation of PTT. Titanium dioxide (TiO2)-based nanomaterials are commonly applied in the biomedicine field, but the weak absorption and low photothermal conversion efficiency (PCE) of TiO2 in the NIR region limit their applications in PTT. Herein, we report the oxygen vacancy engineering that is a robust strategy to regulate the electronic structures of TiO2 for photothermal conversion properties optimizing. The obtained oxygen vacancy-doped TiO2-x nanosheets exhibit strong NIR-II absorption and high PCE owing to their decreased bandgap. Specifically, the PCE of TiO2-x nanosheets is determined to be 69.5 % in the efficient NIR-II window, which is much higher than that of widely reported PTT agents. Complete tumor recession without recurrence or pulmonary metastasis is realized by enhanced NIR-II PTT via TiO2-x nanosheets at an ultralow and safe laser exposure (0.6 W/cm2). Our findings suggest that oxygen vacancy engineering of nanomaterials could regulate their photothermal conversion performances, promoting the further application of TiO2-based nanomaterials in the biomedical.

Hydrothermal Synthesis of Heterostructured g-C3N4/Ag-TiO2 Nanocomposites for Enhanced Photocatalytic Degradation of Organic Pollutants

In this study, heterostructured g-C3N4/Ag-TiO2 nanocomposites were successfully fabricated using an easily accessible hydrothermal route. Various analytical tools were employed to investigate the surface morphology, crystal structure, specific surface area, and optical properties of as-synthesized samples. XRD and TEM characterization results provided evidence of the successful fabrication of the ternary g-C3N4/Ag-TiO2 heterostructured nanocomposite. The heterostructured g-C3N4/Ag-TiO2 nanocomposite exhibited the best degradation efficiency of 98.04% against rhodamine B (RhB) within 180 min under visible LED light irradiation. The g-C3N4/Ag-TiO2 nanocomposite exhibited an apparent reaction rate constant 13.16, 4.7, and 1.33 times higher than that of TiO2, Ag-TiO2, and g-C3N4, respectively. The g-C3N4/Ag-TiO2 ternary composite demonstrated higher photocatalytic activity than pristine TiO2 and binary Ag-TiO2 photocatalysts for the degradation of RhB under visible LED light irradiation. The improved photocatalytic performance of the g-C3N4/Ag-TiO2 nanocomposite can be attributed to the formation of an excellent heterostructure between TiO2 and g-C3N4 as well as the incorporation of Ag nanoparticles, which promoted efficient charge carrier separation and transfer and suppressed the rate of recombination. Therefore, this study presents the development of heterostructured g-C3N4/Ag-TiO2 nanocomposites that exhibit excellent photocatalytic performance for the efficient degradation of harmful organic pollutants in wastewater, making them promising candidates for environmental remediation.

Degradation of levofloxacin in wastewater by photoelectric and ultrasonic synergy with TiO2/g-C3N4@AC combined electrode

A novel particle combined electrode named TiO₂/g-C₃N₄@AC (TGCN-AC) was prepared by loading TiO₂ and g-C₃N₄ on activated carbon through gel method, which was used to degrade levofloxacin (LEF) in pharmaceutical wastewater by photoelectric process. The remarkable physicochemical features of particle electrodes were verified by using diverse characterization techniques including SEM-EDS, XRD, FT-IR, BET and pH_ZPC. EIS-CV and photocurrent showed excellent electrocatalysis and photoelectrocatalysis performance of particle electrodes. The photocatalytic characteristics and fluorescence properties of the particle electrode were proved by UV-vis DRS and PL spectra measurements. Combined with Tauc's plot and Mott-Schottky plots curves, the E_CB and E_VB of particle electrodes were determined. The experiments on different influence factors such as pH, ultrasonic, aeration, current density and the concentration of LEF were carried out in the photoelectric reactor. Under the conditions of pH values 3.0, 200 W ultrasonic, 8 L/min aeration, the mass ratio of g-C₃N₄ and TiO₂ is 8%, after 4.0 h of photoelectric process, about 94.76% of LEF (20 mg/L) in water was degraded. TGCN-AC also has excellent reusability. The degradation rate of LEF can still reach 71.17% after repeated use for 6 times. Scavenger studies showed that h⁺ and O^2- were the main active species. By observing the colony size of E. coli, it was proved that the LEF in the effluent had no antibacterial activity. The degradation pathways of LEF was analyzed and drawn by HPLC-MS spectra.

Wastewater treatment with nanomaterials for the future: A state-of-the-art review

Aquatic and terrestrial ecosystems are both threatened by toxic wastewater. The unique properties of nanomaterials are currently being studied thoroughly for treating sewage. Nanomaterials also have the advantage of being capable of removing organic matter, fungi, and viruses from wastewater. Advanced oxidation processes are used in nanomaterials to treat wastewater. Additionally, nanomaterials have a large effective area of contact due to their tiny dimensions. The adsorption and reactivity of nanomaterials are strong. Wastewater treatment would benefit from the development of nanomaterial technology. Second, the paper provides a comprehensive analysis of the unique characteristics of nanomaterials in wastewater treatment, their proper use, and their prospects. In addition to focusing on their economic feasibility, since limited forms of nanomaterials have been manufactured, it is also necessary to consider their feasibility in terms of their technical results. According to this study, the significant adsorption area, excellent chemical reaction, and electrical conductivity of nanoparticles (NPs) contribute to the successful treatment of wastewater.

A composite photocatalytic system based on spent alkaline Zn-Mn batteries for toluene removal under multiple conditions

The resource utilization of spent alkaline Zn-Mn batteries (S-AZMB) has always been a hot issue in the field of energy regeneration and environmental protection. The cumbersome and complicated purification process is the reason for their limited recycling. Not long ago, we proved that unpurified S-AZMB can be used directly: construct a Z-scheme photocatalytic system by combining with commercial TiO₂ through high-temperature calcination. In order for this finding to be truly adopted by the application market, the high energy consumption calcination process needs to be improved urgently. In this work, we explore the temperature dependence of performance for the composite photocatalyst (TiO₂@S-AZMB). A series of experimental results confirm that lowering the calcination temperature not only conducive to improving the separation efficiency of photogenerated electron-hole pairs, but also can significantly improve the environmental adaptability of the catalyst. Specifically, the catalyst synthesized by calcination temperature at 200 °C exhibits higher toluene removal efficiency than that at 500 °C under different initial concentration of pollutants, relative humidity, light intensity and oxygen content. This study not only further improves the photocatalytic performance of the composite catalyst, but also accords with the idea of energy saving and emission reduction, which provides more space for the possibility of recycling S-AZMB.

High-Stability Ti3C2-QDs/ZnIn2S4/Ti(IV) Flower-like Heterojunction for Boosted Photocatalytic Hydrogen Evolution

The practical application of photocatalytic H₂-evolution is greatly limited by its sluggish charge separation, insufficient active sites, and stability of photocatalysts. Zero-dimensional (0D) Ti₃C₂ MXene quantum dots (MQDs) and amorphous Ti(IV) have been proven to be potential substitutes for noble co-catalyst to accelerate the separation of photogenerated electron-hole pairs and prevent the self-oxidation of photocatalysts, leading to better photocatalytic H₂-evolution performance with long-term stability. In this study, amorphous Ti(IV) and MQDs co-catalysts were successfully deposited on ZnIn₂S₄ (ZIS) microspheres composed of ultra-thin nanosheets via a simple impregnation and self-assembly method (denoted as MQDs/ZIS/Ti(IV)). As expected, the optimal MQDs/ZIS/Ti(IV) sample exhibited a photocatalytic H₂-evolution rate of 7.52 mmol·g⁻¹·h⁻¹ and excellent photostability without metallic Pt as the co-catalyst in the presence of Na₂S/Na₂SO₃ as hole scavenger, about 16, 4.02 and 4.25 times higher than those of ZIS, ZIS/Ti(IV), and MQDs/ZIS, respectively. The significantly enhanced photocatalytic H₂-evolution activity is attributed to the synergistic effect of the three-dimensional (3D) flower-like microsphere structure, the amorphous Ti(IV) hole co-catalyst, and a Schottky junction formed at the ZIS–MQDs interface, which offers more active sites, suppresses self-photocorrosion, and photo-generates the charge recombination of ZIS.

Platinum Crosslinked Carbon Dot@TiO2-x p-n Junctions for Relapse-Free Sonodynamic Tumor Eradication via High-Yield ROS and GSH Depletion

Sonodynamic therapy as a promising noninvasive modality is being developed for tumor therapy, but there is a lack of next-generation sonosensitizers that can generate full ROS at high yields and simultaneously deplete elevated levels of glutathione (GSH) in tumor cells. Semiconductor p-n junctions are engineered as high-efficacy sonosensitizers for sonodynamic tumor eradication using pyridine N-doped carbon dots (N-CDs) as a p-type semiconductor and oxygen-deficient TiO_2-x nanosheets as a n-type semiconductor. The rate constants of ¹ O₂ and •OH generation by ultrasound-excited N-CD@TiO_2-x p-n junctions are 4.3 and 4.5 times higher than those of TiO₂ , respectively. A Z-scheme carrier migration mechanism in the p-n junction achieving the rapid spatial separation of the ultrasound-generated electron-hole pairs for enhanced full ROS production is proposed. GSH-cleavable, Pt-crosslinked, N-doped CD fluorescent probes to detect the presence of intracellular GSH are also constructed. A GSH-responsive, p-n junction platform (Pt/N-CD@TiO_2-x ) with integrated GSH detection, GSH depletion, and enhanced sonodynamic performance is then assembled. Malignant tumors are completely eradicated without relapse via intravenous administration of low-dose Pt/N-CD@TiO_2-x under ultrasound irradiation. This work substantiates the great potential of biocompatible, GSH-responsive p-n junctions as next-generation sonosensitizers via p-n junction-enhanced ROS generation and metal ion oxidation of intracellular GSH.

A Cascade Nanozyme with Amplified Sonodynamic Therapeutic Effects through Comodulation of Hypoxia and Immunosuppression against Cancer

The tumor microenvironment (TME) featured by immunosuppression and hypoxia is pivotal to cancer deterioration and metastasis. Thus, regulating the TME to improve cancer cell ablation efficiency has received extensive interest in oncotherapy. However, to reverse the immunosuppression and alleviate hypoxia simultaneously in the TME are major challenges for effective cancer therapy. Herein, a multifunctional platform based on Au nanoparticles and a carbon dots modified hollow black TiO₂ nanosphere (HABT-C) with intrinsic cascade enzyme mimetic activities is prepared for reversing immunosuppression and alleviating hypoxia in the TME. The HABT-C NPs possess triple-enzyme mimetic activity to act as self-cascade nanozymes, which produce sufficient oxygen to alleviate hypoxia and generate abundant ROS. The theoretical analysis demonstrates that black TiO₂ facilitates absorption of H₂O and O₂, separation of electron-holes, and generation of ROS, consequently amplifying the sonodynamic therapy (SDT) efficiency. Specifically, HABT-C exhibits favorable inhibition of immunosuppressive mediator expression, along with infiltrating of immune effector cells into the TME and reversing the immunosuppression in the TME. As a result, HABT-C can effectively kill tumor cells via eliciting immune infiltration, alleviating hypoxia, and improving SDT efficiency. This cascade nanozyme-based platform (HABT-C@HA) will provide a strategy for highly efficient SDT against cancer by modulation of hypoxia and immunosuppression in the TME.

Ag and MOFs-derived hollow Co3O4 decorated in the 3D g-C3N4 for creating dual transferring channels of electrons and holes to boost CO2 photoreduction performance

The rapid recombination of photoinduced charge carriers and low selectivity are still challenges for the CO₂ photoreduction. Herein, we proposed that ZIF-67-derived Co₃O₄ hollow polyhedrons (CoHP) were embedded into NaCl-template-assisted synthesized 3D graphitic carbon nitride (NCN), subsequently, loading Ag by photo-deposition as efficient composites (CoHP@NCN@Ag) for CO₂ photoreduction. This integration simultaneously constructs two heterojunctions: p-n junction between Co₃O₄ and g-C₃N₄ and metal-semiconductor junction between Ag and g-C₃N₄, in which Co₃O₄ and Ag serve as hole (h⁺) trapping sites and electron (e^-) sinks, respectively, achieving spatial separation of charge carriers. The donor-acceptor structure design of NCN realize a good photogenerated e^--h⁺ separation efficiency. The mesoporous structure of hollow Co₃O₄ facilitate gas-diffusion efficiency, light scattering and harvesting. And the introduction of plasmonic Ag further strengthens the light-harvesting and charge migration. Benefiting from the rational design, the optimized ternary heterostructures exhibit a high CO₂-CO yield (562 μmol g^-1), which is about 4-fold as high as that of the NCN (151 μmol g^-1). Moreover, the conjectural mechanism was systematically summarized. We hope this study provides a promising strategy for designing efficient g-C₃N₄ systems for the CO₂ photoreduction.

Construction of three-dimensional MgIn2S4 nanoflowers/two-dimensional oxygen-doped g-C3N4 nanosheets direct Z-scheme heterojunctions for efficient Cr(VI) reduction: Insight into the role of superoxide radicals

Environmental crisis aroused from carcinogenic and mutagenic heavy metal Cr(VI)-containing wastewater has attracted great attention. Herein, a direct Z-scheme three-dimensional MgIn₂S₄ nanoflowers/two-dimensional oxygen-doped g-C₃N₄ nanosheets heterostructured composite photocatalysts were fabricated for Cr(VI) photoreduction. The crystalline structure, morphology, specific surface areas, chemical components, optical properties, as well as photoelectrochemical performance of the fabricated photocatalyst were systematically studied. All the hybrids photocatalysts exhibited superior Cr(VI) photoreduction performance than a single component. The optimal sample showed 2.0 and 343.7 times increasing than three-dimensional MgIn₂S₄ nanoflowers and two-dimensional oxygen-doped g-C₃N₄ nanosheets, respectively. The enhancement of the Cr(VI) photoreduction performance could be ascribed to the enhanced specific surface areas, the improved light absorption, and the Z-scheme charge carriers' separation and migration pathway. Moreover, the role of superoxide radicals was investigated. It is speculated that this research would present a new sight toward photocatalytic Cr(VI) reduction.

In situ synthesis of holey g-C3N4 nanosheets decorated by hydroxyapatite nanospheres as efficient visible light photocatalyst

The interesting g-C3N4 nanosheet morphology has drawn huge attention in photocatalytic applications because of its special features. Nonetheless, the relative activity of these nanosheets is still controversial due to the low available active sites and the high recombination probability of photo-induced charge carriers. In this work, in situ sol-gel approach was applied to synthesize holey g-C3N4 nanosheets/hydroxyapatite (HAp) nanospheres with plentiful in-plane holes. Herein, the presence of Ca2+ plays a key role in the formation of holey defects on 2D g-C3N4. In-plane holes provide nanosheets with more active edges and diffusion channelsv, resulting in a tremendous enhanced mass and photo-induced charge transfer speed. Moreover, the holes make highly numbered boundaries, which lead to the prevention of aggregation. On the other hand, distributed nano-HAp spheres on these nanosheets can form effective heterojunctions having high photo-degradation ability of pollutants. Intrinsic O-vacancies inside HAp unit cells mainly affect the capture of photogenerated electrons, pollutant molecules, and O2 gas. The synergistic presence of O-vacancies and holey defects (C-vacancies) on 2D g-C3N4 plays a key role in raising the photocatalytic performance of holey g-C3N4/HAp. It can be concluded that the proposed preparation method is a promising approach for simultaneous synthesis of holey g-C3N4 and surface heterojunctions of Ca-based materials. This new structure has shown significant degradation ability of bisphenol A, a prominent pollutant, with a low amount (0.01 g) and short time.

Improving the photodynamic therapy of pyropheophorbide a through the combination of hypoxia-sensitive molecule and infrared light-excited d-TiO2−X nanoparticles

Photodynamic therapy (PDT) involving the generation of cytotoxic reactive oxygen species under light in the presence of sufficient oxygen has been widely used in diagnosing and treating cancer. However, the ubiquitous hypoxia in many solid tumors due to their abnormal proliferation and vascularization has greatly compromised the therapeutic effect. We have designed and prepared a tumor therapeutic nanoplatform for improving PDT based on defective TiO[Formula: see text] (d-TiO[Formula: see text] with the consideration that the continuous PDT would cause hypoxic tumor microenvironment (HTM) in which many hypoxia-sensitive drugs might be activated to exert the antitumor activities. The inorganic d-TiO[Formula: see text] nanoparticles (NPs) were firstly prepared and then modified by APTES to obtain the mesoporous d-TiO[Formula: see text]@SiO2NPs. The organic photosensitizer pyropheophorbide-a (PPa) and hypoxic-sensitive agent 6-aminoflavone (AF) were then adsorbed in the mesoporous SiO2, followed by further hydrophilic PEGylation to improve the biocompatibility. Defective d-TiO[Formula: see text] and the PPa could simultaneously consume oxygen after light excitation, while the resulted HTM was utilized to activate the hypoxic-sensitive agent 6-aminoflavone (AF) to trigger anti-cancer effect. The prepared d-TiO[Formula: see text]@SiO2/PPa/AF@PEG NPs were stable in normal physiological environment, and could continuously release PPa and AF under slightly acidic conditions. The in vitro experiments against cancer cells suggested that the combination of PPa and AF displayed significantly enhanced antitumor activities than that of monotherapy. Therefore, this research offered a potential application for 6-aminoflavone in PDT-induced hypoxia to improve the antitumor effects.

Defect enrich ultrathin TiO2 nanosheets for rapid adsorption and visible light mediated PPCPs degradation

Recently, PPCPs have attracted extensive attention as emerging pollutants. Due to the strong hydrophilicity and small molecular weight, PPCPs are difficult to be fully removed by adsorption and other processes, posing a serious threat to the ecological environment. Here, we demonstrate solvothermal synthesis of defect enrich TiO₂ nanosheets through simple copper doping. Novel TiO₂ nanosheets were found to be mesoporous with high specific surface area and exhibited excellent visible light response. Performance of the developed TiO₂ nanosheets were evaluated towards photocatalytic degradation of two model pollutants, tetracycline and acetaminophen. Results showed robust degradation of tetracycline and acetaminophen under visible-light irradiation within 100 min. Meanwhile, the potential relationship between the structural characteristics and excellent ability of the catalyst was discussed, as well as probable mechanism. Additionally, a study on the toxicity of tetracycline solution to human skin epidermal cells showed that the toxicity of the treated solution to cells is greatly reduced. The prepared catalysts show good repeatability (a slightly decrease ca.3% after 5 cycles) and applicability, providing a reasonable design for water remediation.

Polarization-enhanced photoelectrochemical properties of BaTiO3/BaTiO3-x/CdS heterostructure nanocubes

With the aim of improving the photocatalytic activity for water splitting, novel core-shell-structured crystalline-BaTiO₃/amorphous-BaTiO_3-x/crystalline-CdS composite nanocubes are prepared by a facile two-step synthesis approach. Basic characterization techniques such as X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and transmission electron microscopy are carried out on the as-prepared composite nanocubes in order to confirm the quality of their crystal structure, morphology and chemical components correspondingly. UV-Vis-NIR measurements of the as-prepared composite nanocubes validate the presence of extended visible-light absorbance due to oxygen-deficient BaTiO_3-x. Photoelectrochemical tests are carried out on the as-prepared nanocomposite films that are coated directly on indium tin oxide (ITO) glass substrates. The as-prepared composite nanocubes show a photocurrent density of 100 μA cm^-2 without electric field poling, whereas they show about 200 μA cm^-2 with an electric field poling of 18.8 kV cm^-1. This study suggests that the photoelectrochemical performance is highest in our prepared BaTiO₃/BaTiO_3-x/CdS composite film compared to the pure BaTiO₃, CdS and BaTiO₃/BaTiO_3-x films, and it may offer a new potential route for designing cost-effective, highly stable and efficient photocatalysts.

Plasmonic ZnO/Au/g-C3N4 nanocomposites as solar light active photocatalysts for degradation of organic contaminants in wastewater

In the present study, novel ZnO/Au/graphitic carbon nitride (g-C₃N₄) nanocomposites were fabricated via a facile and eco-friendly liquid phase pulsed laser process followed by calcination. Notably, the approach did not necessitate the use of any capping agents or surfactants. The as-prepared photocatalysts were evaluated by various electron microscopy and spectroscopy techniques. The obtained results confirmed good dispersion of the Au nanoparticles (NPs) on the surface of spherical ZnO particles deposited on the g-C₃N₄ nanosheets. The ZnO/Au/g-C₃N₄ nanocomposite exhibited substantially enhanced catalytic activity toward the degradation of methylene blue (MB) under simulated solar light irradiation. In particular, the ZnO/Au15/g-C₃N₄ composite containing 15 wt% Au displayed a rate constant, which was approximately 3 and 5 times greater than those of pristine g-C₃N₄ and ZnO, respectively. This improved photocatalytic activity of ZnO/Au15/g-C₃N₄ was attributed to the surface plasmon resonance of Au NPs and the synergistic effects between ZnO and g-C₃N₄. The boundary between ZnO/Au and g-C₃N₄ enabled direct migration of the photogenerated electrons from g-C₃N₄ to ZnO/Au, which hindered the recombination of electron-hole pairs and enhanced the carrier separation efficiency. Additionally, a plausible MB degradation mechanism over the ZnO/Au/g-C₃N₄ photocatalyst is proposed based on the results of the conducted scavenger study.

Self-photoreduced Ag0-doped Ag(i)–organic frameworks with efficient visible-light-driven photocatalytic performance

A series of Ag0-doped Ag(i)organic frameworks have been constructed via a facile self-photoreduction strategy and can be applied as efficient photocatalysts for the photocatalytic degradation of methyl orange.

Cobalt-based ZIF coordinated hybrids with defective TiO2-x for boosting visible light-driven photo-Fenton-like degradation of bisphenol A

Designing heterostructure of photocatalyst as an efficient approach to boost visible light-driven photocatalytic degradation, we prepared a series of cobalt-based ZIF coordinated with defective TiO_2-x, denoted as B-TiO_2-x@ZIF-67 composites, through wrapping defective B-TiO_2-x on ZIF-67 for promoting photocatalytic degradation efficiency of biphenyl A. The B-TiO_2-x@ZIF-67 composites displayed superior photocatalytic performance to pure TiO_2-x or ZIF-67 because of faster separation of photogenerated charge carriers and more suitable redox potentials. Such a novel photo-Fenton-like system composed of B-TiO_2-x@ZIF-67/H₂O₂/visible light accelerated the peroxidative degradation of biphenyl An up to a removal efficiency of 95.30%, which is also higher than that of photocatalysis or Fenton-like reaction alone. In addition, the degradation efficiency of biphenyl A is unchanged after catalyst reuse of four cycles. Integrating the trapping experiments and electrochemical analysis, we found the oxygen vacancy on B-TiO_2-x capturing the electrons to promote the separation of photogenerated charges, meanwhile the Co(II) in the composite decomposed hydrogen peroxide (H₂O₂) to produce more •OH radical. Both of them mutually boosted the removal efficiency. Finally, feasible degradation pathways of biphenyl A were proposed based on the assay of LC-MS spectrometry. This strategy offers a novel insight into fabrication of Co-ZIF-based TiO_2-x materials and application to visible light-driven photocatalytic and Fenton-like degradation reaction.

Enhanced visible light photocatalytic activity of Fe2O3 modified TiO2 prepared by atomic layer deposition

In this work, commercial anatase TiO2 powders were modified using ultrathin Fe2O3 layer by atomic layer deposition (ALD). The ultrathin Fe2O3 coating having small bandgap of 2.20 eV can increase the visible light absorption of TiO2 supports, at the meantime, Fe2O3/TiO2 heterojunction can effectively improve the lifetime of photogenerated electron-hole pairs. Results of ALD Fe2O3 modified TiO2 catalyst, therefore, showed great visible light driven catalytic degradation of methyl orange compared to pristine TiO2. A 400 cycles of ALD Fe2O3 (~ 2.6 nm) coated TiO2 powders exhibit the highest degradation efficiency of 97.4% in 90 min, much higher than pristine TiO2 powders of only 12.5%. Moreover, an ultrathin ALD Al2O3 (~ 2 nm) was able to improve the stability of Fe2O3-TiO2 catalyst. These results demonstrate that ALD surface modification with ultrathin coating is an extremely powerful route for the applications in constructing efficient and stable photocatalysts.

An innovative magnetic Ni0.1Co0.9Fe2O4/g-C3N4 nano-micro-spherical heterojunction composite photocatalyst with an extraordinarily prominent visible-light-irradiation degradation performance toward organic pollutants

Environmental pollution removal is attracting more attention these days because of increasing environmental problems. The use of photodegradation catalysts is a promising avenue in resolving environmental issues and therefore high-performance photocatalysts are urgently needed. Herein, we solvothermally synthesized a micro-spherical g-C3N4 photocatalyst and a nanospherical Ni0.1Co0.9Fe2O4 photocatalyst, and then innovatively employed small amounts of Ni0.1Co0.9Fe2O4 nanospheres coupled with g-C3N4 microspheres to fabricate a novel magnetic Ni0.1Co0.9Fe2O4/g-C3N4 nano-micro-spherical heterojunction photocatalyst through post co-calcination. Various techniques, including scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform-infrared spectroscopy and UV-vis diffuse reflectance spectroscopy, were employed to analyze the as-synthesized hybrid photocatalyst. The resultant photocatalyst exhibits a record high photocatalytic degradation activity against methylene blue under visible-light irradiation with a 100% degradation rate within only 10 min, corresponding to an extraordinarily prominent degradation reaction rate constant k value of up to 0.586 min-1. Our strategy opens a new effective way for fabricating high-performance photocatalysts and our novel Ni0.1Co0.9Fe2O4/g-C3N4 heterojunction photocatalyst is of great potential for application in environmental treatments.

Recent Developments of Advanced Ti3+-Self-Doped TiO2 for Efficient Visible-Light-Driven Photocatalysis

Research into the development of efficient semiconductor photocatalytic materials is a promising approach to solving environmental and energy problems worldwide. Among these materials, TiO2 photocatalysts are one of the most commonly used due to their efficient photoactivity, high stability, low cost and environmental friendliness. However, since the UV content of sunlight is less than 5%, the development of visible light-activated TiO2-based photocatalysts is essential to increase the solar energy efficiency. Here, we review recent works on advanced visible light-activated Ti3+-self-doped TiO2 (Ti3+–TiO2) photocatalysts with improved electronic band structures for efficient charge separation. We analyze the different methods used to produce Ti3+–TiO2 photocatalysts, where Ti3+ with a high oxygen defect density can be used for energy production from visible light. We categorize advanced modifications in electronic states of Ti3+–TiO2 by improving their photocatalytic activity. Ti3+–TiO2 photocatalysts with large charge separation and low recombination of photogenerated electrons and holes can be practically applied for energy conversion and advanced oxidation processes in natural environments and deserve significant attention.

Co3O4-Ag photocatalysts for the efficient degradation of methyl orange

In this paper, a series of Co3O4-Ag photocatalysts with different Ag loadings were synthesized by facile hydrothermal and in situ photoreduction methods and fully characterized by XRD, SEM, TEM, FTIR spectroscopy, XPS, UV-vis and PL techniques. The catalysts were used for the degradation of methyl orange (MO). Compared with the pure Co3O4 catalyst, the Co3O4-Ag catalysts showed better activity; among these, the Co3O4-Ag-0.3 catalyst demonstrated the most efficient activity with 96.4% degradation efficiency after 30 h UV light irradiation and high degradation efficiency of 99.1% after 6 h visible light irradiation. According to the corresponding dynamics study under UV light irradiation, the photocatalytic efficiency of Co3O4-Ag-0.3 was 2.72 times higher than that of Co3O4 under identical reaction conditions. The excellent photocatalytic activity of Co3O4-Ag can be attributed to the synergistic effect of strong absorption under UV and visible light, reduced photoelectron and hole recombination rate, and decreased band gap due to Ag doping. Additionally, a possible reaction mechanism over the Co3O4-Ag photocatalysts was proposed and explained.

Araneose Ti3+ self-doping TiO2/SiO2 nanowires membrane for removal of aqueous MB under visible light irradiation

Araneose Ti³⁺ self-doped TiO₂/SiO₂ nanowires (RTiO₂/SiO₂) were prepared and anchored onto a polyethersulfone (PES) membrane. Careful characterizations and measurements indicated a covalent grafting of SiO₂ onto reduced TiO₂ (RTiO₂) through Ti-O-Si linkages, acquiring uniformed RTiO₂/SiO₂ nanowires of almost complete anatase and benign hydrophilicity. The RTiO₂/SiO₂-based PES membrane showed a significantly enhanced visible light-driven degradation rate of methylene blue (MB) (90.7%), compared with that on bare PES (11.1%) and PES-RTiO₂ (59.6%) membranes. The residual MB in filtered water was less than 5% after reusing three times. The normalized permeate flux of the modified membrane was 0.83, and the transmembrane pressure only increased by 0.4 MPa under irradiation of visible light. The improved performance of the PES-RTiO₂/SiO₂ was attributed to efficient intercept of MB molecular, light harvesting of visible light, and separation of charge carriers on araneose RTiO₂/SiO₂ nanowires.

Photocatalytic Properties of Copper Nitride/Molybdenum Disulfide Composite Films Prepared by Magnetron Sputtering

Cu3N/MoS2 composite films were prepared by magnetron sputtering under different preparation parameter, and their photocatalytic properties were investigated. Results showed that the composite films surface was uniform and had no evident cracks. When the sputtering power of MoS2 increased from 2 W to 8 W, the photocatalytic performance of the composite films showed a trend of increasing first and then decreasing. Among these films, the composite films with MoS2 sputtering power of 4 W showed the best photocatalytic degradation performance. The photocatalytic degradation rate of methyl orange at 30 min was 98.3%, because the MoS2 crystal in the films preferentially grew over the Cu3N crystal, thereby affecting the growth of the Cu3N crystal. The crystallinity of the copper nitride also increased. During photocatalytic degradation, the proper amount of MoS2 reduced the band gap of Cu3N, and the photogenerated electron hole pairs were easily separated. Thus, the films produces additional photogenerated electrons and promotes the degradation reaction of the composite films on methyl orange solution.

MOF-derived TiO2 modified with g-C3N4 nanosheets for enhanced visible-light photocatalytic performance

A g-C₃N₄/TiO₂ heterojunction was prepared for the first time using a mechanical agitation method assisted by a template method and a two-step calcination method.

Facile synthesis of porous C-doped C3N4: fast charge separation and enhanced photocatalytic hydrogen evolution

A facile gaseous-bubbles templating approach to synthesize porous C-doped g-C₃N₄ with enhanced photocatalytic activity for hydrogen evolution reaction.

Promoted spatial charge separation of plasmon Ag and co-catalyst Co x P decorated mesoporous g-C3N4 nanosheet assembly for unexpected solar-driven photocatalytic performance

Plasmon Ag and co-catalyst Co _x P decorated mesoporous graphite carbon nitride nanosheet assemblies have been synthesized via a template-calcination and ball milling strategy combined with photoreduction. The obtained composites are characterized by x-ray diffraction, Fourier transmission infrared spectroscopy, x-ray photoelectron spectroscopy, transmission electron microscopy, and UV-vis diffuse reflectance spectroscopy. The results show that the sample assembly with mesoporous structure has specific surface area of 50.4 m² g^-1, pore size of 11.3 nm and pore volume of 0.21 cm³ g^-1. The Ag and Co _x P nanoparticles are decorated on the surface of graphite carbon nitride uniformly. Under solar light irradiation, the photocatalytic degradation rate of ceftazidime for the prepared sample assembly is up to ∼92%, and the photocatalytic reaction rate constant is about 10 times higher than that of bare graphite carbon nitride. Moreover, the sample assembly also exhibits a solar-driven photocatalytic hydrogen production rate of 96.66 μmol g^-1 h^-1. It can attributed to the surface plasmon resonance effect of Ag nanoparticles and Co _x P co-catalyst promoting the spatial charge separation and the mesoporous structure providing more surface active sites and favoring mass transfer. This special structure offers new insights for fabricating other high-performance photocatalysts with high spatial charge separation.

Surface-defect-rich mesoporous NH2-MIL-125 (Ti)@Bi2MoO6 core-shell heterojunction with improved charge separation and enhanced visible-light-driven photocatalytic performance

Mesoporous NH₂-MIL-125(Ti)@Bi₂MoO₆ core-shell heterojunctions with surface defects were fabricated through a facile solvothermal method. The mesoporous core-shell structure with a large relative surface area of 87.7 m² g^-1 and narrow pore size of 8.2 nm extends the photoresponse to the range of visible light due to the narrow band gap of ∼1.89 eV. The visible-light-driven photocatalytic degradation efficiency of highly toxic dichlorophen and trichlorophenol were 93.28 and 92.19%, respectively, and the corresponding rate constants were approximately 8 and 17 times higher than the rates achieved by pristine NH₂-MIL-125(Ti). The photocatalytic oxygen production rate was increased to 171.3 µmol g^-1. Recycling for several cycles indicates high stability, which is favorable for practical applications. The excellent photocatalytic performance can be ascribed to the formation of the core-shell heterojunctions and to the surface defects that favor charge separation and visible light absorption; the mesoporous structure offers an adequate number of surface active sites and mass transfer. This novel mesoporous core-shell photocatalyst will have potential applications in the environment, and this strategy offers a new insight into fabrication of other high-performance core-shell structure photocatalysts.