Efficient Visible-light Photocatalytic Performance Research Articles

Efficient visible light photocatalytic performance of bismuth trioxide/titanium dioxide composite for selective conversion of glucose to arabinose and formic acid

The photocatalytic valorization of glucose has attracted more and more attention for producing value-added chemicals. Herein, value-added chemicals like arabinose and formic acid were obtained by selective photocatalytic oxidation of glucose irradiated with visible light, which was realized using Bi2O3/TiO2 composite as the photocatalyst and atmospheric O2 as the oxidant in water. It was found that the photocatalytic performance of Bi2O3/TiO2 composite in the glucose oxidation was obviously superior to that of pure Bi2O3 and pure TiO2, the significantly enhanced photocatalytic efficiency was mainly attributed to the promotion of photogenerated charge separation and adsorption capacity towards glucose. The influences of mass ratio of Bi2O3 to TiO2 and initial concentration of glucose on the glucose oxidation were further investigated with many details. Additionally, recycling experiments showed that the Bi2O3/TiO2 composite exhibited a favorable stability in the photocatalytic process, and the roles of various active species for glucose oxidation were also determined by the active species trapping experiments. This work could provide some valuable viewpoints for producing value-added chemicals from biomass by photocatalysis.

Flower like Ni doped BiVO4 composite with efficient visible light photocatalytic performance for the removal of Naproxen: A detailed mechanism and DFT study

BiVO4 and Ni doped BiVO4 (Ni-BiVO4) photocatalysts were synthesised by the co-precipitation method. BiVO4 and Ni-BiVO4 photocatalysts were characterized by various analytical techniques. PXRD studies of the BiVO4 and Ni-BiVO4 catalysts shows monoclinic-scheelite structure. Density functional theory calculations were carried out to predict the density of states and band gaps. The flower bunch is arrayed in a rod-like pattern on the HRTEM images, and the particle size was estimated using d-spacing and found to be in the range of 98-415 nm. Furthermore, the charge separation mechanism of photogenerated charge carriers of BiVO4 and Ni-BiVO4 photocatalysts were studied by photoelectrochemical response and impendence spectroscopy. The result shows that the Ni-BiVO4 photocatalyst possess the higher photocatalytic performance, and this can be attributed to the enhanced absorption of visible light, and lower recombination of electron and holes. Further, enhanced photocatalytic activity of Ni-BiVO4 photocatalyst was observed by addition of hydrogen peroxide (H2O2). The order of photocatalytic activity for the degradation of Naproxen under visible light: Ni-BiVO4 +H2O2 > Ni-BiVO4 > BiVO4 > Ni-BiVO4 + IPA. The investigation of degradation products was carried out utilising liquid chromatography mass spectroscopy coupled UV-visible absorption spectrum technique. Radical quenching is studied to reveal the substantial contribution of hydroxyl free radicals in the Ni-BiVO4 with H2O2 system.

0D/2D Nb2O5/ZnIn2S4 heterojunctions with enhanced utilization of light and separation of photogenerated carrier for efficient visible light photocatalytic performance

0D/2D heterojunctions via the single-photon excitation can avoid the light shielding of non-active component to promote the photocatalytic activity. However, it is very difficult to prepare ultrasmall nanoparticles loaded on 2D nanosheets via one pot method. Heren, we fabricated a Nb2O5/ZnIn2S4 (Nb-ZIS) heterojunction via a simple solvothermal process assisted by the Na2CO3 and thioacetamide (TAA), where zero-dimensional (0D) ultra-small Nb2O5 particles (≈10 nm) are uniformly in-situ grown on two-dimensional (2D) ZnIn2S4 nanosheets (ZIS). Structural characterizations and density functional theory (DFT) calculation suggest that the 0D-on-2D interface can not only alleviate the blocking effect of light, promoting light absorption for photocatalytic process, but also enhances the separation of photon-generated carriers through the built-in electric field (BIEF). Encouragingly, the Nb-ZIS heterojunction shows significant enhancement for H2 evolution and degradation of lignin, where the hydrogen evolution rate reaches 5.4 mmol h−1 g−1 and the lignin degradation rate achieves 78.5%, surpassing the commercial block Nb2O5 supported on ZIS heterojunction (Nb-ZIS-C) (4.0 mmol h−1 g−1 for hydrogen evolution and 61.9% for degradation) and the 0.2Nb/ZIS without the addition of Na2CO3 (4.5 mmol h−1 g−1 for hydrogen evolution and 72.3% for degradation), respectively.

DBD plasma assisted synthesis of MO@Fe/Ce-MOFs with rich oxygen defects as efficient photocatalysts for nitrogen fixation

A series of metal oxide/ metal-organic frameworks (MOFs) composites (MO@Fe/Ce-MOFs) were synthesized by partial thermal decomposition of Fe/Ce-MOFs which were synthesized with dielectric barrier discharge (DBD) plasma. The heterojunction interface between MOFs and metal oxides can effectively promote the electron interface transfer. When Fe was introduced, the energy band of the catalysts became narrower, and the increase of oxygen defects concentration slowed down the recombination rate of photogenerated electrons and holes, which greatly improved the photocatalytic performance. MO@Fe/Ce-MOFs exhibited more efficient visible light photocatalytic performance than that of Fe/Ce-MOFs. MO@Fe/Ce-MOFs-b (the molar ratio of Fe to Ce is 1:3) formed an abundant oxygen defect that facilitated the photocatalytic nitrogen fixation reaction. For MO@Fe/Ce-MOFs-b, the NH4+ generation rate reached 299 μmol·L−1·h−1 after 2 h photoreaction under visible light with N2 and deionized water as solvent. Also, MO@Fe/Ce-MOFs-b showed high cyclic stability. After three repeated cycles, the NH4+ generation rate maintained about 95%. This work provided a new method for the preparation of MO@MOFs and emphasized the importance of oxygen defects in nitrogen fixation.

Highly efficient visible-light photocatalytic performance of MOFs-derived TiO2 via heterojunction construction and oxygen vacancy engineering

Novel Z-scheme ZnIn2S4/TiO2-x photocatalyst was successfully fabricated through self-sacrificing template-chemical bath deposition combined with a NaBH4 reduction method for the first time. It was found that ZnIn2S4/TiO2-x exhibited high-efficient visible-light photocatalytic RhB degradation of 91 % within 40 min, which was almost 45.5, 1.2, and 6.1 times better than that of TiO2, ZnIn2S4/TiO2, and TiO2-x, respectively. Moreover, an obscure change in catalytic activity can be observed after five recycles. The excellent photocatalytic performance can be attributed to the synergistic effect of Ov, ZnIn2S4, and MOF-derived TiO2, which extend the visible-light photoresponse range and promote the separation of photo-generated charge carriers.

Construction of Bi/Polyoxometalate doped TiO2 composite with efficient visible-light photocatalytic performance: Mechanism insight, degradation pathway and toxicity evaluation

Exploration of visible-light-responsive, efficient and durable photocatalysts is of great concern for removing organic dyes and antibiotics from the wastewater. Herein, a series of mesoporous TiO2-doped with polyoxometalates [H3PMo12O40] (PMo12) and loaded with Bi nanoparticles (NPs) composites were fabricated through a convenient electrospinning/calcination and hydrothermalmethods, which was labelled as × wt% Bi/PMo12 doped TiO2 (abbr. x% Bi/PT, x = 10, 20 and 30, respectively). In these composites, polyoxometalate PMo12 acts as a dopant to reduce the band gap value of TiO2, effectively expanding its visible light absorption and enhance its photocatalytic redox ability. Moreover, the Schottky junction between Bi NPs and PT further promotes the separation efficiency of the photoinduced carriers. Therefore, these as-prepared catalysts demonstrated outstanding and persistent photocatalytic activity for removing tetracycline (TC), enrofloxacin (EFA) and methylorange (MO) with visible-light (λ > 420 nm) illumination. Especially, 20 % Bi/PT specimen presented the optimal catalytic performance, whose degradation efficiencies for TC, EFA and MO reached 86.0 %, 90.9 % and 92.5 % with k = 0.03019, 0.01275 and 0.01199 min−1, respectively. The superoxide radical (⋅O2–), hydroxyl radical (⋅OH) and holes (h+) were proved to be the dominating active species in contaminants degradation through the trapping tests and electron spin resonance (ESR) measurements. Furthermore, the possible TC degradation pathways were established based on the identification of degradation products by high performance liquid chromatography-mass spectrometry (HPLC-MS). The toxicity of intermediates was also assessed through QSAR prediction. According to the energy band structure analysis, the corresponding photocatalytic mechanism was revealed. The current work provides several new insights for the design and preparation of low cost, efficient, stable and versatile photocatalysts.

Hierarchical ZnS layers-coated Ti3+-TiO2 nanostructures for boosted visible-light photocatalytic norfloxacin degradation

Self-doped Ti3+-TiO2 and amorphous ZnS layers-coated Ti3+-TiO2 nanostructures were successfully fabricated for via a calcination-ultrasonic synthesis strategy for organic pollutant degradation under visible-light illumination. The experimental results revealed that the synthesized Ti3+-TiO2 clusters displayed efficient visible-light absorption and photocatalytic performance. It was also found that amorphous ZnS layers were formed on the coral-like Ti3+-TiO2 clusters via an ultrasonic synthesis method, and the strongly combined interfaces greatly boosted the charge separation between ZnS layers and self-doped Ti3+-TiO2 clusters. The synthesized Ti3+-TiO2@ZnS-15% heterojunction presented the highest photocatalytic activity with a rate constant of 0.03197 min−1, approximately 9.87 times of commercial TiO2. In addition, the prepared Ti3+-TiO2@ZnS composites also exhibited highly boosted photocatalytic performance towards ciprofloxacin and tetracycline degradation under visible-light illumination compared with those of commercial TiO2, Ti3+-TiO2, and ZnS samples. Finally, the norfloxacin degradation pathways and visible-light photocatalytic mechanism over nanostructured Ti3+-TiO2@ZnS heterojunctions were suggested.

Preparation of Ag@AgCl/GO Material with Efficient Visible-Light Photocatalytic Performance

Ag@AgCl/GO was prepared by chemical coupling, in-situ deposition of supported AgCl, and photoreduction. The morphology, structure, and surface area of the prepared Ag@AgCl/GO were characterized by SEM, TEM, FT-IR, Raman spectra, and BET. The optical properties of the photocatalyst were analyzed by PL and UV-Vis DRS, respectively. The surface electrical properties and degradation stability were evaluated by zeta potential measurement and cyclic catalytic degradation experiments, and the photocatalytic mechanism was proposed in detail based on the ESR test and trapping experiment. The results showed that Ag@AgCl nanoparticles were spherical and cluster distributed on the folded structure of GO. The prepared Ag@AgCl/GO had good adsorption performance and photocatalytic degradation stability. The material showed good visible light catalytic performance; especially, the degradation rates of cationic dyes RhB and MB were significantly higher than those of anionic dyes MO and CR, and their degradation processes were in line with the quasi-first-order reaction kinetics. Holes (h+) and superoxide radicals (·O2－) were the main active species for the degradation of RhB.

Negative inductive effect enhances charge transfer driving in sulfonic acid functionalized graphitic carbon nitride with efficient visible-light photocatalytic performance

Efficient photogenerated carrier migration/separation plays a critical role in increasing the photocatalytic performance of g-C3N4. Herein, sulfonic acid group-functionalized g-C3N4 (SACN) was synthesized and then synchronously strengthened by a facile-solid-state thermal reaction of g-C3N4 and sulfamic acid. As a solid strong acid, sulfamic acid can be used to achieve acid etching on the surface of g-C3N4 with the assistance of thermal treatment, leading to an enlarged specific surface area and increased surface catalytic reaction sites. More importantly, our experiments and density functional theory calculations indicate that the driving force generated by the negative inductive effect of sulfonic acid groups significantly improves the charge transfer dynamics and effectively inhibits their recombination. Moreover, the negative inductive effect can induce charge redistribution, which reduces the conduction band potential of g-C3N4 to enhance the reduction ability of photo-induced electrons. As a result, the SACN-400 sample showed excellent photocatalytic performance in H2 generation with an apparent quantum efficiency of 11.03% at 420 ± 15 nm, as well as an efficient photodegradation rate for organic pollutants.

Construction of Bi/Polyoxometalate Doped Tio2 Composite with Efficient Visible-Light Photocatalytic Performance: Mechanism Insight, Degradation Pathway and Toxicity Evaluation

Construction of Bi/Polyoxometalate Doped Tio2 Composite with Efficient Visible-Light Photocatalytic Performance: Mechanism Insight, Degradation Pathway and Toxicity Evaluation

Graphitic Carbon Nitride Codoped with Sulfur and Yttrium for Efficient Visible-Light Photocatalytic Performance

The correlation of electronic band structure and photocatalytic performance of graphitic carbon nitride (g-C3N4) provides important perspectives for understanding the catalytic mechanism and develo...

One‐Step Fabrication of 2D/2D Z‐Scheme BiOCl/g‐C3N4 Nanosheets Heterojunction for Efficient Degradation of RhB and Cr(VI) Ions Reduction under Visible‐Light Illumination

AbstractTo promote the utilization efficiency of solar energy, a one‐step strategy to fabricate 2D/2D Z‐scheme BiOCl/g‐C3N4 nanosheets (BiOCl/CNs) heterojunction through the in‐situ growth of BiOCl on CNs was studied. Here, we report that ultrathin CNs with wrinkled surface are prepared by a rapid cooling method. The wrinkled surface of CNs provided more active sites for BiOCl to anchor on it thus facilitating the formation of the tight heterojunction structure via a solvothermal process. The as‐prepared BiOCl/CNs hybrid photocatalysts was confirmed by various physicochemical characterizations. The results showed the uniform distribution of BiOCl nanoflakes on g‐C3N4 nanosheets and formation of 2D/2D Z‐scheme heterojunction structure. The as‐prepared BiOCl/CNs‐5 photocatalyst displays extraordinarily photocatalytic activity for the photocatalytic degradation of RhB and Cr(VI) reduction under visible light irradiation, about 94 % RhB and 93 % Cr(VI) was degraded in 100 min. The remarkable photocatalytic properties were attributed to the Z‐scheme hierarchical structure, large specific surface and efficient charge carrier separation. Furthermore, the Z‐scheme photocatalytic reaction mechanism was presented to elucidate the improved photocatalytic activity of BiOCl/CNs photocatalyst. The photodegradation of phenol and radical species trapping experiments were conducted to prove the formation of Z‐scheme. This work provides a facile route for the construction of g‐C3N4 based Z‐scheme structure photocatalyst for efficient visible light photocatalytic performance.

Ultrathin carbon-coated Zr3+-ZrO2 nanostructures for efficient visible light photocatalytic antibiotic elimination

Broadband solar light absorption and visible light photocatalysis of surface modified ultrawide bandgap semiconductors are receiving wide attentions because of their more negative conduction band potential and positive valence band potential for refractory organics degradation. Here, we reported a novel modified solvothermal strategy by the introduction of distilled water into small molecular alcohols to synthesize crystallized carbon-coated Zr3+-ZrO2 composites for enhanced visible light absorption and visible light photocatalytic tetracycline degradation, in which the distilled water favored for the crystallization of Zr3+-ZrO2 and the formed ultrathin carbon layers derived from the polymerization of small molecular alcohols were contributing to the generation of Zr3+ species and well dispersion of Zr3+ self-doped ZrO2 nanoparticles. The experimental results also showed that carbon-coated Zr3+-ZrO2 composites exhibited enhanced visible light absorption, long-lived charges, efficient visible light photocatalytic performance and good recyclable stability. Besides, possible photocatalytic mechanism and antibiotic degradation pathways over carbon-coated Zr3+-ZrO2 composites under visible light irradiation were also proposed in detail.

Nickel-Doping accelerated charge separation in flower ball-like Bi4O5I2 for efficient visible-light photocatalytic performance

Ion-doped semiconductor photocatalysts were considered to be an important strategy to improve photocatalytic performance. A simple one-step solvothermal method was used to prepare flower ball-shaped Bi4O5I2 nanomaterials modified by Nickel. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra, photocurrent response and EIS Nyquist plots were used to explore its structural composition and photoelectrochemical properties. The photocatalytic activity was studied by simulating the degradation of tetracycline under visible light. The degradation results showed that photocatalytic effect of 5 wt% Ni-doped Bi4O5I2 was the best among the samples, and the degradation rate was 91%. The capture experiment shown that the vital active radical is O2–. The final results shown that Ni-doping improved the charge separation efficiency and the specific surface area of the material, and it is proved by Raman that Ni-doping formed shallow traps on the surface of Bi4O5I2, which promoted the separation and transfer of carriers and improved the photocatalytic activity. This work can provide a reference for the subsequent development of bismuth-based photocatalysts.

Synthesis of novel ternary heterojunctions via Bi2WO6 coupling with CuS and g-C3N4 for the highly efficient visible-light photodegradation of ciprofloxacin in wastewater

In this study, the novel Bi2WO6/CuS/g-C3N4 ternary heterojunctions with highly efficient visible-light photocatalytic performance were synthesized, which were then applying in the degradation of ciprofloxacin (CIP) in wastewater. The characterization data demonstrated that the heterojunction interfaces were formed between Bi2WO6, CuS and g-C3N4, which effectively narrowed the band gap. Moreover, coupling CuS with g-C3N4 inhibited the recombination of photogenerated e− and h+ pairs and accelerated the interfacial charge transfer; as a result, Bi2WO6/CuS/g-C3N4 possessed enhanced visible-light photocatalytic performance. Importantly, it has been confirmed that the photogenerated e−, h+ and O2−were main active species generated by Bi2WO6/CuS/g-C3N4 for photodegradation, which realized simultaneous redox reactions for the effective degradation of CIP (74.94 %, 75 min) and RhB (99.66 %, 90 min). Besides, the great chemical stability enabled Bi2WO6/CuS/g-C3N4 to maintain nearly the same photodegradation efficiency for CIP degradation after four repeated cycles. Taken together, this study provided not only a feasible method for synthesizing the novel Bi2WO6/CuS/g-C3N4 ternary heterojunctions with highly efficient visible-light photocatalytic performance, but also a way for purifying CIP in wastewater.

Sonochemical synthesis of PANI-BiVO4-GO semiconductor nanocomposite highly efficient visible-light photocatalytic performance

Polyaniline/Bismuth Vanadate/Graphene Oxide (PANI-BiVO4-GO) or BGPA composite was prepared by sonochemical deposition of bismuth vanadate-graphene oxide (BiVO4) nanoparticles on the surface of polyaniline (PANI). The best photocatalytic degradation performance was obtained by 5wt% BGPA composites for MB, RhB, and SO dyes, which is approximately 4 times higher than that of 1% BGPA. Meanwhile, the photocatalytic stability of BiVO4 was significantly improved by introducing PANI into the PANI-BiVO4-GO composite. The dramatic promotion of the photocatalytic degradation performance and the photocatalytic stability can be attributed to the formation of a heterojunction free electron between PANI and BiVO4-GO. The existence of those extra free electrons can dramatically enhance the efficiency of the photogenerated electrons, which accelerate the transfer of photogenerated holes from BiVO4-GO to PANI, and therefore inhibit the self-oxidation of BiVO4.

Co-monomer engineering optimized electron delocalization system in carbon-bridging modified g-C3N4 nanosheets with efficient visible-light photocatalytic performance

The bridged nitrogen that linked each melem unit in g-C3N4 is considered to be sp3 hybridization with a high electronegativity, which confines the original conjugate system of melon networks. Herein, the carbon-bridging modified g-C3N4 nanosheet (CBCN) is prepared by a one-pot copolymerization for the first time through employing malondiamide (MLDD) as a novel polymerized small molecule to urea. Experimental and DFT computation identify that substituting parts of bridged nitrogen in melon units with carbon not only improves the original conjugate system and optimizes the band structure of g-C3N4, but also induces the charges redistribution, leading to an enhanced charges separation and visible light utilization. Moreover, the MLDD co-monomer can act as a blocking agent to generate structure edge defects, which results in numerous in-plane holes and increases the specific surface area greatly. As a result, the CBCN samples show an excellent photocatalytic performance in degradation of pollutants and H2 generation.

(Invited) Semiconductor Nanomaterials for Photoelectrochemical Solar Fuel Generation

Semiconducting materials hold the key for efficient photocatalytic and photoelectrochemical water splitting. In this talk, we will give a brief overview of our recent progresses in designing semiconductor metal oxides materials for photoelectrochemical energy conversion including photocatalytic solar fuel generation. In more details, we have been focusing the following a few aspects; 1) band-gap engineering of layered semiconductor compounds including layered titanate, tantalate and niobate-based metal oxide compounds for visible light phtocatalysis, and 2) facet-controlled TiO2, Fe2O3, BiVO4 and perovskites as building blocks for new photoelectrode design，and 3) the combination of a high performance photoelectrode BiVO4 with perovskite solar cells can lead to unassisted solar driven water splitting process with unassisted solar-to-hydrogen conversion efficiency of >6.5%; The resultant material systems exhibited efficient visible light photocatalytic performance and improved power conversion efficiency in solar energy, which underpin important solar-energy conversion applications including solar fuel generation and simultaneous environmental application.

Efficient visible-light photocatalytic performance of CdS/BiPO4 nanoparticles fabricated by solvothermal method

Visible-light CdS/BiPO4 nanoparticles were prepared by a solvothermal method. The as-prepared CdS/BiPO4 nanoparticles were characterized by scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (UV–vis DRS) and photoluminescence (PL). The CdS/BiPO4 nanoparticles exhibited better photocatalytic performance and higher stability of photodegradation of malachite green (MG). And the highest photodegradation rate of MG is up to 98 %. In addition, the mechanism of photocatalysis was demonstrated based on the radical-trapping experiments. The performance of CdS/BiPO4 nanoparticles in photocatalysis is mainly attributed to the carriers separation and electron migration from CdS to BiPO4 efficiently via intimate contact with the interface. The heterojunction formed by CdS/BiPO4 is helpful to inhibit the recombination of electrons and holes.This work puts forward a viewpoint for the design of CdS/BiPO4 nanoparticles in order to making use of solar energy more efficiently and providing some perspectives on the process of photo-generated carrier migration.

In-situ self-assembly synthesis of 2D/2D CdS/g-C3N4 heterojunction for efficient visible-light photocatalytic performance

Novel 2D/2D CdS/g-C3N4 heterojunction was prepared successfully simply by in-situ hydrothermal process assisted with microwave. The effect of g-C3N4 incorporation ratio on the photocatalytic activity of the composites was discussed. The physical and optical properties of the samples were characterized in detail. CdS/g-C3N4-50 wt% showed the best MO degradation efficiency, which was more than 5 times higher than pure g-C3N4. The intimate contact surface from the formation of 2D/2D CdS/g-C3N4 heterojunction improved the separation ratio of photo-induced electron-hole pairs under visible-light illumination. This study provides a new way for constructing efficient 2D/2D photocatalysts for more applications in photocatalytic area.