High Efficiency Visible Light Research Articles

Reasonable design of roman cauliflower photocatalyst Cd0.8Zn0.2S, high-efficiency visible light induced hydrogen generation

Previous reports indicate that the catalyst CdxZn1−xS shows good activity and reliability in the process of photocatalytic hydrogen production. However, it is still a challenge to design a cost-effective catalyst to replace the traditional CdxZn1−xS. In this work, Roman broccoli Cd0.8Zn0.2S-2 was successfully prepared through reasonable adjustment and control of the amount of raw materials. In the photocatalytic hydrogen evolution test, the amount of hydrogen evolution of CZS-2 was 1.24, 1.34, 2.06, and 2.24 times that of CZS-1, CZS-3, CZS-4, and CZS-5, respectively. This is because Cd0.8Zn0.2S-2 has more excellent synergy inside. Theoretical and experimental studies show that, based on rational design, the optical and electrical properties of the CZS-2 structure have been substantially improved (based on UV–Visible diffusion and photoluminescence). The mechanism of the study shows that the photocatalytic hydrogen evolution activity of CZS-2 is effectively improved due to the favorable energy band of effective charge transfer inside CZS-2. In this work, Roman broccoli-like CZS-2 provides a new research direction for photocatalytic water decomposition.

Synthesis of Li-doping tetragonal-Bi2O3 nanomaterial with high efficient visible light photocatalysis

In this work, LixBiOy compounds were synthesized via a facile calcination method. It was surprising that the as-prepared Li7BiO6 compounds transformed into Li-doping tetragonal Bi2O3 phase after undergoing water washing disposal, which was well verified by combining XRD and HR-TEM. In addition, the energy bandgap of prepared compound was derived based on UV–Vis diffuse reflectance spectrum and results indicate the formation of a lower band gap when increasing Li dopant concentration. Moreover, the Li-doping tetragonal Bi2O3 exhibited high visible light-driven photocatalytic activity and the methylene blue can be well degraded in 10 min. The enhanced photocatalytic activity was ascribed to the improvement of light response and charge transfer. Our current work will boost the development of photocatalysis and bring insight into other LixMO6 (e.g., Li6WO6, Li7TabO6, Li7NbO6, Li8ZrO6) compounds to extend their photocatalytic application.

SBA-15 Templated Mesoporous Graphitic C3N4for Remarkably Enhanced Photocatalytic Degradation of Organic Pollutants under Visible Light

Organic pollutants in water have been threatening public and environmental health. Developing efficient and sustainable photocatalysts working for degradation of organic pollutants under visible light becomes a big challenge. In this paper, high-efficiency visible light driven catalyst ordered mesoporous graphite nitride carbon (mpg-C3N4) was prepared by using SBA-15 as template and dicyandiamide (C2H4N4) as precursor. The specific surface area of mpg-C3N4can be increased remarkably as compared to that of the bulk graphite nitrite carbon (g-C3N4) by adjusting the ratio of SBA-15 to dicyandiamide. Photocatalytic performance of mpg-C3N4were evaluated systematically by degradation of Rhodamine B (RhB), malachite green (MG) and tetracycline hydrochloride (TC) under visible light irradiation. The results showed that the mpg-C3N4(1:0.5) has the highest photocatalytic activity and stability and the degradation rate is for RhB, MG and TC are all more than seven times that of bulk g-C3N4. After five recycling runs, the mpg-C3N4(1:0.5) remains high photocatalytic activities for the degradation of MG (94%) and TC (81%), respectively. Additionally, radical trapping experiments certified that the main active species are [Formula: see text] and h[Formula: see text], while the role of [Formula: see text]OH is irrelevant in the reaction processes. This work provides a promising pathway to prepare metal-free photocatalyst for degradation of organic pollutants under visible light irradiation.

Synthesis of Graphene Oxide Interspersed in Hexagonal WO3 Nanorods for High-Efficiency Visible-Light Driven Photocatalysis and NH3 Gas Sensing

WO3 nanorods and GO (at 1 wt% loading) doped WO3 were synthesized using a template free deposition-hydrothermal route and thoroughly characterized by various techniques including XRD, FTIR, Raman, TEM-SAED, PL, UV-Vis, XPS, and N2 adsorption. The nano-materials performance was investigated toward photocatalytic degradation of methylene blue dye (20 ppm) under visible light illumination (160 W, λ> 420) and gas sensing ability for ammonia gas (10–100 ppm) at 200°C. HRTEM investigation of the 1%GO.WO3 composite revealed WO3 nanorods of a major d-spacing value of 0.16 nm indexed to the crystal plane (221). That relevant plane was absent in pure WO3 establishing the intercalation with GO. The MB degradation activity was considerably enhanced over the 1%GO.WO3 catalyst with a rate constant of 0.0154 min−1 exceeding that of WO3 by 15 times. The reaction mechanism was justified dependent on electrons, holes and •OH reactive species as determined via scavenger examination tests and characterization techniques. The drop in both band gap (2.49 eV) and PL intensity was the main reason responsible for enhancing the photo-degradation activity of the 1%GO.WO3 catalyst. The later catalyst initiated the two electron O2 reduction forming H2O2, that contributed in the photoactivity improvement via forming •OH moieties. The hexagonal structure of 1%GO.WO3 showed a better gas sensing performance for ammonia gas at 100 ppm (Ra-Rg/Rg = 17.6) exceeding that of pure WO3 nanorods (1.27). The superiority of the gas-sensing property of the 1%GO.WO3 catalyst was mainly ascribed to the high dispersity of GO onto WO3 surfaces by which different carbon species served as mediators to hinder the recombination rate of photo-generated electron-hole pairs and therefore facilitated the electron transition. The dominancy of the lattice plane (221) in 1%GO.WO3 formed between GO and WO3 improved the electron transport in the gas-sensing process.

Fabricated rGO-modified Ag2S nanoparticles/g-C3N4 nanosheets photocatalyst for enhancing photocatalytic activity

Photocatalytic technology provides a new strategy for the treatment of water pollution and energy crisis. Developing photocatalytic materials with high efficiency and stable visible light response has always been the direction of scientific researchers in the photocatalytic field. In this paper, we designed and prepared an efficient and stable rGO-modifited type-I Ag2S/g-C3N4 heterojunction photocatalyst (rGO/Ag2S/CN). The TEM (Transmission electron microscope) technology shows that the morphology of rGO/Ag2S/CN is a sandwich-like structure. UV–Vis DRS (UV–visible diffuse-reflectance spectrum) shows that the loading of Ag2S NPs and the modification of rGO effectively enhance the light response performance of nanocomposite materials in visible light. PL (Photoluminescence) and PEC (Photoelectrochemical) results prove that the photogenerated carriers transport and separation efficiency of rGO/Ag2S/CN have been improved. The photodegradation of RhB and the photoreduction of CO2 results confirmed that this ternary nanocomposite has great photocatalytic activity. The photodegradation efficiency of the RhB aqueous solution is about 98.5% after 30 min under the visible light irradiation. The photoreduction experiments showed that the yields of CO and CH4 are 178.05 μmol/g and 121.11 μmol/g, respectively after 8 h under the UV light irradiation. The results of cyclic photocatalytic experiments and the XRD pattern after those processes further revealed that the modification of rGO not only enhanced the photocatalytic performance of the nanocomposite photocatalyst, but also effectively improved the stability of Ag2S in the photocatalytic process. The possible photocatalytic reaction mechanisms were discussed in detail.

High-Efficiency Visible Light Responsive Sulfide KSb5S8 Photocatalyst with a Layered Crystal Structure

The development of efficient photocatalysts for degrading environmental pollutants in wastewater has drawn considerable attention due to their great potential in industrial applications. Herein, we used a solvothermal method to prepare KSb5S8 with a layered crystal structure. The crystal structure of the as-synthesized samples was characterized by powder X-ray diffraction and transmission electron microscope imaging. Our UV-vis diffuse reflectance spectroscopy results indicated that KSb5S8 could absorb visible light, and its optical band gap was 1.62 eV. The photocatalytic activity of KSb5S8 was evaluated in the degradation of methyl orange. A degradation of 73% within 180 min was achieved under visible light irradiation, which was considerably higher than that of commercial P25 and g-C3N4. Theoretical calculations demonstrated that KSb5S8 was an indirect band gap semiconductor. The estimated effective mass of holes ( m h * ) was approximately two times greater than that of electrons ( m e * ) . The large ratio of m h * / m e * might promote separation of photo-induced carriers during the photocatalytic process. On the basis of the layered crystal structure and large m h * / m e * value, KSb5S8 was a high-performance photocatalyst capable of harvesting visible light. This study provides valuable insight that will aid the design of improved sulfide photocatalytic materials with layered crystal structures.

Synthesis and characterization of 2D/0D g-C3N4/CdS-nitrogen doped hollow carbon spheres (NHCs) composites with enhanced visible light photodegradation activity for antibiotic

Herein, the high surface area and efficient visible light (VSL) induced photocatalyst, namely 2D/0D g-C3N4/CdS-nitrogen doped hollow carbon spheres (NHCs) composites have been prepared. Firstly, the physicochemical, photoelectric and electronic structures (including band structure, density of state and charge density difference) properties of the obtained samples were studied. Then, the photocatalytic experiments indicated that the g-C3N4/CdS-NHCs composites performed a markedly improved VSL photocatalytic performance and photostability for cloxacillin antibiotic degradation compared with pure g-C3N4, CdS and g-C3N4/CdS heterojunction. The enhanced photocatalytic performance of g-C3N4/CdS-NHCs composites could ascribe to the synergy between g-C3N4/CdS heterojunction and NHCs, which obviously improved the specific surface area, the absorption of VSL, the transfer rate of electrons and the separation efficiency of photogenerated electron-hole pairs of the photocatalysts. Finally, the mechanism analysis showed that active substances h+, O2−, and OH worked together in the photocatalytic process, which attack the β-lactam, thiazolidine ring and amide group should be the fatal act for CLX mineralization.

High-efficiency visible light photocatalytic performances of the CdS(HS)/g-C3N4 composites: the role of intimate connection and hollow structure

The CdS(HS)/g-C3N4 photocatalysts with an intimate connection was successfully synthesized by a facile deposition method. The CdS hollow microspheres (CdS(HS)) were well anchored on the surface of g-C3N4 to form an intimate connection by the hydrogen bonding between g-C3N4 and CdS(HS). The structures, morphologies, optical and electrical properties and photocatalytic performance of samples were successfully characterized by multiple means. The CdS(HS)/g-C3N4 composites exhibited excellent photocatalytic activity and stability for the photodegradation of RhB, and the degradation rate constant of CdS(HS)/g-C3N4 with optimum CdS(HS) mass ratio of 0.25% was about 2.1 times higher than that of the pure g-C3N4 under the visible light irradiation for 20 min. After four cycles, the CdS(HS)(0.25%)/g-C3N4 composite still maintained the high photocatalytic activity with the RhB degradation efficiency of 95%. Surprisingly, the photocorrosion of CdS(HS) caused by the photogenerated holes was inhibited effectively. The improvement of these properties should be ascribed to the intimate connection between g-C3N4 and CdS(HS) and the hollow structure of CdS(HS). The photocatalytic mechanism was also analyzed systematically. Furthermore, it was of great interest that the CdS(HS)/g-C3N4 composites possessed an excellent sedimentation property and they can be easily separated from the solution, which will be propitious to practical application.

Fabrication of high efficiency visible light Z-scheme heterostructure photocatalyst g-C3N4/Fe0(1%)/TiO2 and degradation of rhodamine B and antibiotics

Abstract We have prepared and studied a novel low cost catalyst of g-C3N4/Fe0(1%)/TiO2, using a simple process involving the formation of zero valence iron by chemical reduction. This ternary catalyst g-C3N4/Fe0(1%)/TiO2 was characterized using XRD (X-Ray diffraction), UV–vis spectrum, EDS (Energy Dispersive spectrum) and TEM (transmission electron microscopy), it demonstrated high-visible-light activity in a wide range of pH condition, it can photo-catalytically degraded Rhodamine B (RhB), Tetracycline (TC), and Berberine hydrogen chloride (BH) (∼98% in 90 min) under visible light. The high activity arises from the increased harvest of more visible light and the improved separation of photo-excited electrons and holes via Z-scheme and heterojunctions mechanism. Also, the time required to remove 100% RhB, TC, and 96% BH can be shortened from 90 min to 60 min by introducing 3.18 mM Na2SO3 to this photocatalysis system that assisted the generation of reactive oxidizing species and pollutant degradation. The results showed promising application prospect for this developed catalyst and the tested photocatalysis pollutant degradation system.

Ni doped noble-metal-free CdZnNiS photocatalyst for high-efficient photocatalytic hydrogen evolution reduction by visible light driving

In this paper, we report a method that the transition element nickel is doped into the interstitial position of CdZnS (CZS) nanoparticles for their photocatalytic hydrogen evolution activity boosting. It is demonstrated that CdZnNiS nanocrystalline materials (with 0.5 wt% of Ni) could achieve the highest photocatalytic H2-evolution activity of 25.4 mmol·g−1·h−1 in sulfide and sulfite solution under visible light which value is 1.16 times higher than that of Pt modified CdZnS particles (with 3 wt% of Pt). This work evidences the possibility of substitution of noble metal cocatalyst by adding a suitable inexpensive Ni to achieve high-efficient visible light driven water splitting hydrogen production.

Removing Cr (VI) in water via visible-light photocatalytic reduction over Cr-doped SrTiO3 nanoplates

It is crucial to develop a high-efficiency visible-light responsive photocatalyst for settling the increasing contamination stemmed from toxic heavy metal ions in wastewater. In this study, Cr-doped SrTiO3 (CrSTO) nanoplates were synthesized by a facile one-pot solvothermal method with ethylene glycol as both the solvent and morphology controller. The resultant CrSTO nanoplates are about 100 nm in size and 20 nm in thickness, which are composed of SrTiO3 nanocrystals about 19 nm in diameter. Furthermore, they possess the mesopore 3.0 nm in size, endowing their much higher specific surface area than the commercial SrTiO3 particles. The Cr element is doped into the crystal lattice of SrTiO3 by the substitution of Cr3+ for Sr2+, which enables the absorption edge redshift to the visible light region, thus elevating the visible-light absorption capability. In addition, the CrSTO-0.9 nanoplate with 0.9% Cr element content exhibits the highest photocatalytic performance for the Cr(VI) reduction under visible light irradiation, which can reduce nearly all Cr(VI) within 3.5 h and preserve the excellent stability after six recycles. This kind of CrSTO nanoplates may serve as a potential and promising photocatalyst for efficient Cr(VI) removal in wastewater.

Porous N-doped TiO2 nanotubes arrays by reverse oxidation of TiN and their visible-light photocatalytic activity

Highly ordered porous N-doped TiO2 nanotubes arrays (N-TiO2 NTAs) are produced via reverse oxidation of porous TiN NTAs in air atmosphere. The band gap of produced porous N-TiO2 NTAs was reduced from 3.04 eV for TiO2 NTAs to 2.94 eV. Photocatalytic (PC) investigations indicate that the porous N-TiO2 NTAs exhibit three times larger visible light PC kinetic rate constant than that of anatase TiO2 NTAs as a result of the enhanced visible light activity and the large surface area. The results demonstrate that reverse oxidation of nitride is an applicable method for the preparation of nitrogen doping oxide and could be potential using for the fabrication of other carbon or sulfur doped oxide by oxidation of corresponding carbide and sulfide for high efficient visible light photocatalyst.

Z-scheme BCN-TiO2 nanocomposites with oxygen vacancy for high efficiency visible light driven hydrogen production

BCN-TiO2 nanocomposites are obtained by a simple calcination method using a hexagonal boron carbon nitride (BCN) semiconductor and nanotubular titanic acid (NTA) as precursors. The BCN-TiO2 nanocomposites are characterized systematically by XRD, TEM, XPS, DRS, ESR, BET, I-t and PL techniques. Compared with the novel TiO2 or single BCN sample, the BCN-TiO2 nanocomposites prepared by a calcination method show the highest photocatalytic activity for hydrogen production under visible-light irradiation. The photocatalytic activity of BCN-TiO2 nanocomposites is optimized by changing the amount of BCN. Characterization results confirm that a large amount of single electron oxygen vacancies can be formed when NTA was calcined at the higher temperature, which is beneficial to the enhancement of visible light absorption and the transfer of photogenerated carriers due to the formation of ohmic contact at the interface between BCN and novel TiO2. Therefore, the visible light photocatalytic activity for H2 production of BCN-TiO2 nanocomposites has been improved significantly by the formation of BCN-TiO2 Z-scheme photocatalyst, which results in efficient space separation of photo-induced charge carriers.

Preparation and Photochemical Properties of Layered MoS2/Cu2o Heterojunction Nanocomposites

In recent years, environmental problems induced by organic pollutants have become an important problem for our society. Semiconductor photochemical treatment is a potential technology for solving the environmental issues. Therefore, lots of efforts have been devoted to develop high-efficiency visible light assisted semiconductor photocatalysts. Cu2O nanoparticle is a well-known p-type semiconductor with a direct band gap of 2.17eV, which endows it a reasonable alternative for photocatalytic applications [1-3]. However, high recombination rate of the electron-hole pairs excited from Cu2O nanoparticles seriously hinders its practical application. Coupling p-type Cu2O nanoparticles with n-type semiconductor to form a P-N heterojunction for carrier separation and produce appropriate energy level difference for charge transfer from one semiconductor to another is a potential approach to decrease recombination rate for high-efficiency degradation. Graphene-like n-type semiconductor MoS2 multilayered nanoplates are the reasonable alternative due to its tunable bandgap with different layers and large amounts of unsaturated active sites [4-5]. In this work, two-dimensional (2D) MoS2 nanoplates with different multilayer thickness were prepared by liquid exfoliation and gradient centrifugation. Then, the MoS2 nanoplates were utilized to match the energy level of Cu2O nanoparticles to form MoS2/Cu2O nanocomposites, which have been achieved by the method of hydrothermal synthesis. Scanning Electrom Microscope images and X-ray diffraction (XRD) pattern of nanoparticles Cu2O and MoS2/Cu2O nanocomposites are shown in Fig.1. It can be seen that the morphology of Cu2O nanoparticles are truncated octahedron structure and closely attached on MoS2 nanosheets with different thickness, which was obtained at the centrifugation speed of 2000 rpm, 4000 rpm, 6000 rpm and 8000 rpm. The photochemical behaviors of Cu2O nanoparticles and different MoS2/Cu2O nanocomposites are characterized through the degradation behaviors of methyl orange (MO) under visible light irradiation (Fig.2). The experimental results show that the degradation efficiency of MoS2/Cu2O nanocomposites can be improved by optimizing the thickness of MoS2 nanoplates from few layers to bulk. The degradation ratios of MO after 3 h are 57.9%, 61.1%, 92.2%, 95.3%, 93.1%, and correspond respectively to the MoS2/Cu2O nanocomposites in which the MoS2 nanosheets were obtained at the centrifugation speed of 0 rpm, 2000 rpm, 4000 rpm, 6000 rpm and 8000 rpm. The possible reason is that the increasing surface area and bandgap of MoS2 may provide large reaction area and produce appropriate energy level difference, which is beneficial for accelerating the degradation process of methyl orange. In summary, the different MoS2/Cu2O heterojunction nanocomposites were prepared through adjusting the thickness of multilayered MoS2 nanoplates. The results show that the optimized degradation ratio of MO can be greatly improved from 57.9% up to 95.3% after 3h using MoS2/Cu2O nanocomposites in comparison with Cu2O nanoparticles.

Carbon-Doped Mesoporous Anatase TiO2 Multi-Tubes Nanostructures for Highly Improved Visible Light Photocatalytic Activity.

Development of a high surface area and efficient visible light induced photocatalyst on a large scale is a promising task from the practical perspective. In this study, visible light active C-doped anatase TiO2 multi-tubes were synthesized using banana (Musa acuminata) stem fiber as a sacrificial template, removed by calcination at 450 °C. During the calcination process, the lattice of anatase TiO2 phase was doped with C, and obtained multi-tubes showed high surface area (∼99 m2/g) with a mesoporous structure made of ∼15 ± 3 nm nanoparticles. The synthesized TiO2 multi-tubes showed an enhanced light absorption property in the whole visible light region and good thermal stability of the anatase phase up to 750 °C. The synthesized C-doped TiO2 multi-tubes manifest an excellent photocatalytic activity for the reduction of Cr (VI) to Cr(III) under the visible light exposure. This process may have lots of practical importance as the method of synthesis of the catalyst is novel and the multi-tubes structure can be synthesized on a large scale through a quick and economical way with excellent photocatalytic activity. This novel multi-tubes structure may also be useful for photovoltaics, antimicrobial, and Li-batteries applications in the future.

A novel strategy to fabricate plasmonic Ag/AgBr nano-particle and its enhanced visible photocatalytic performance and mechanism for degradation of acetaminophen

Abstract In the present work, plasmonic Ag/AgBr nano-particle was fabricated by solution reduction strategy. Meanwhile, physicochemical properties of the resulting samples were investigated by series of techniques. Results showed that Ag/AgBr nano-particle exhibited intense light absorbance in the whole visible region, high photoinduced charge separation efficiency and visible light driven PC performance. Furthermore, the enhanced visible light PC mechanism was proposed and confirmed. Besides, the PC degradation pathways of acetaminophen were elucidated based on the UPLC-MS/MS measurement. Results indicated that five degradation intermediates were detected, consequently two tentative pathways for PC degradation of acetaminophen were proposed, for example hydroxylation addition to parent compound and C N cleavage of side chain from the acetaminophen attacked by photoinduced holes. This study provides a facile and feasible strategy to fabricate high-efficient visible light response of nano-materials which can be applied in the fields of waste water treatment.

NiS and MoS2 nanosheet co-modified graphitic C3N4 ternary heterostructure for high efficient visible light photodegradation of antibiotic

The development of efficient solar driven catalytic system for the degradation of antibiotics has become increasingly important in environmental protection and remediation. Non-noble-metal NiS and MoS2 nanosheet co-modified graphitic C3N4 ternary heterostructure has been synthesized via a facile combination of hydrothermal and ultrasound method, and the ternary heterostructure has been utilized for photocatalytic degradation of antibiotic agents. The antibiotics of ciprofloxacin (CIP) and tetracycline hydrochloride (TC) were photodegraded by the hybrid under the visible light. The optimal photodegradation rate of the ternary heterostructure reaches about 96% after 2h irradiation, which is 2.1 times higher than that of pure g-C3N4 for TC degradation. The photocatalytic degradation rates of the ternary heterostructure for both CIP and TC obey the pseudo-first-order kinetic model. The enhanced visible light adsorption and charge separation efficiency contribute to the photocatalytic performance of the ternary heterostructure. This work provides new insights and pathways by which efficient degradation of antibiotics can be achieved and will stimulate further studies in this important field.

Novel (3D, 1D and 2D) of WO3/TiO2NT–graphene ternary nanocomposites for high efficiency visible light photocatalysis

Novel (3D, 1D and 2D) of WO3/TiO2NT–graphene ternary nanocomposites for high efficiency visible light photocatalysis

Atomic thin titania nanosheet-coupled reduced graphene oxide 2D heterostructures for enhanced photocatalytic activity and fast lithium storage

Realizing practical high performance materials and devices using the properties of 2D materials is of key research interest in the materials science field. In particular, building well-defined heterostructures using more than two different 2D components in a rational way is highly desirable. In this paper, a 2D heterostructure consisting of atomic thin titania nanosheets densely grown on reduced graphene oxide surface is successfully prepared through incorporating polymer functionalized graphene oxide into the novel TiO2 nanosheets synthesis scheme. As a result of the synergistic combination of a highly accessible surface area and abundant interface, which can modulate the physicochemical properties, the resultant heterostructure can be used in high efficiency visible light photocatalysis as well as fast energy storage with a long lifecycle.

Precise control of Cu2O nanostructures and LED-assisted photocatalysis

We describe the synthesis and characterization of a high-efficiency visible light Cu2O photocatalyst.