Electrostatic self-assembly of 2D-2D CoP/ZnIn2S4 nanosheets for efficient photocatalytic hydrogen evolution

Constructing efficient and cost-effective photocatalysts are highly desirable for photocatalytic hydrogen evolution. Herein, we prepare a unique 2D-2D architecture photocatalyst composed of CoP and ZnIn₂S₄ (ZIS) nanosheets through electrostatic self-assembly method. The constructed 2D-2D CoP/ZIS exhibit a remarkably enhanced photocatalytic performance with hydrogen production rate of 8.775 mmol g⁻¹ h⁻¹, and this value is much higher than ZIS and most of other ZIS-based nanohybrids. Additionally, the nanohybrids possess excellent stability with 96.3% of initial activity remaining after 24 hours of testing. These satisfactory results are attributed to the large/intimate contact interface and the photo/electro-chemical properties of ZIS and CoP, which improves light absorption, facilitates photoelectron transport and suppresses charge recombination. This work not only demonstrates ZIS nanosheet can serve as a versatile and effective platform supporting non-noble metal nanosheets to boost their photocatalytic performance, but also offers a general and simple electrostatic self-assembly method to design 2D-2D-based heterostructures for hydrogen conversion from water splitting.     

0D CoP cocatalyst/ 2D g-C3N4 nanosheets: An efficient photocatalyst for promoting photocatalytic hydrogen evolution

In this work, cobalt phosphide (CoP) nanoparticles were successfully decorated on an ultrathin g-C₃N₄ nanosheet photocatalysts by in situ chemical deposition. The built-in electric field formed by heterojunction interface of the CoP/g-C₃N₄ composite semiconductor can accelerate the transmission and separation of photogenerated charge-hole pairs and effectively improve the photocatalytic performance. TEM, HRTEM, XPS, and SPV analysis showed that CoP/g-C₃N₄ formed a stable heterogeneous interface and effectively enhanced photogenerated electron-hole separation. UV-vis DRS analysis showed that the composite had enhanced visible light absorption than pure g-C₃N₄ and was a visible light driven photocatalyst. In this process, NaH₂PO₂ and CoCl₂ are used as the source of P and Co, and typical preparation of CoP can be completed within 3 hours. Under visible light irradiation, the optimal H₂ evolution rate of 3.0 mol% CoP/g-C₃N₄ is about 15.1 μmol h⁻¹. The photocatalytic activity and stability of the CoP/g-C₃N₄ materials were evaluated by photocatalytic decomposition of water. The intrinsic relationship between the microstructure of the composite catalyst and the photocatalytic performance was analyzed to reveal the photocatalytic reaction mechanism.     

Constructing 0D/1D/2D Z-scheme heterojunctions of Ag nanodots/SiC nanofibers/g-C3N4 nanosheets for efficient photocatalytic water splitting

Efficiently constructing nanostructured Z-scheme heterojunctions with good interface contact is a desired route to optimize the photocatalytic property of the materials. In this work, novel 0D/1D/2D Z-scheme silver/silicon carbide/graphitic carbon nitride (Ag/SiC/CN) photocatalysts were prepared from Ag nanodots loaded on SiC nanofibers/CN nanosheets (SiC/CN) composite, using the calcination and chemical reduction routes. The Ag/SiC/CN composite with an optimal 3% Ag loading dose performs the best H₂ evolution rate of 2971 μmol g^?1 h^?1, which is approximately 8.8, 1.5 and 4.5 times compared to CN, SiC/CN and 3% Ag/CN, respectively. Besides the Ag/SiC/CN composite presents a high apparent quantum efficiency (7.3%) and outstanding photo-corrosion resistance stability. The Ag nanodots are served as efficient carriers transfer center and cocatalyst to construct Z-scheme heterojunction interface, which can help to generate more photo-generated carries, shorten the electron transmission distance and increase the electron transfer rate, certifying that 0D/1D/2D Z-scheme photocatalytic system is high-efficiency and has great advantages in photocatalytic applications.     

Preparation of Sn‐doped CdS/TiO2/conducting polymer fiber composites for efficient photocatalytic hydrogen production under visible light irradiation

Sn‐doped CdS/TiO₂ heterojunction was synthesized on the conducting polymer fiber mat by hydrothermal method. The conducting polymer fiber mat was made by electrospinning from polyvinylidene fluoride, styrene‐maleic anhydride copolymer, and nano‐graphites as conducting fillers. The Sn‐doped CdS/TiO₂ heterojunction was characterized by XRD, XPS, SEM, TEM, TGA, and UV–Vis absorption spectra. Under simulated solar light irradiation, a combination of Sn‐doped CdS/TiO₂/conducting polymer was found to be highly efficient for photocatalytic hydrogen evolution from splitting of water. The photocatalytic hydrogen production efficiency was up to 2885 μmol h^?1 g^?1cat. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42300.     

Thickness controlled and smooth polycrystalline CVD diamond film deposition on SiO2 with electrostatic self assembly seeding process

Sub micrometer thick continuous CVD diamond film was synthesized on thermally grown SiO₂ film employing the electrostatic self assembly seeding with nano-meter sized ultra dispersed diamond particles. Hot filament CVD system was used to deposit diamond film. Formation of mono-dispersed and mono-layered nano diamond seeding layer by well-known Electrostatic Self-Assembly method was effective to increase density and homogeneity of seeding particles. Because of high density of uniformed seeding particles, the nm controlled continuous CVD films with the surface roughness of less than 13 nm on silicon oxide without any mechanical damage were obtained. Linear growth rate with short incubation time was also observed. Depending on the film thickness, coloring effect was observed ranging from blue to yellow and orange. There was no visible fringe on the coated surface which affirms the good thickness uniformity.     

2D/2D nanohybrid of Ti3C2 MXene/WO3 photocatalytic membranes for efficient water purification

Photocatalytic membrane is attracting a great deal of current attention for water decontamination by taking the full advantage of photocatalysis and membrane separation. Herein, the well-defined WO₃ nanoplates are homogeneously dispersed onto the surface of multilayer Ti₃C₂ MXene to create a novel 2D/2D nanohybrid with various Ti₃C₂ contents (3–7 wt%) through a facile and cost-effective approach, and then photocatalytic membrane system is developed by anchoring these heterostructured-photocatalysts on polyvinylidene fluoride (PVDF) membrane by means of vacuum filtration. Ti₃C₂/WO₃/PVDF photocatalytic membranes exhibit enhanced RhB degradation and cyclability, alongside with refreshing behavior under visible-light illumination. We demonstrate that the excellent electrical conductivity of Ti₃C₂, the formation of built-in electric field and the large interface contact area between Ti₃C₂ and WO₃ synergetically promote the spatial charge separation and increase the surface reactive sites, which is responsible for boosting the photoreactivity and photostability. Besides, a significant high flux recovery of ～ 94% is obtained by 5 wt% Ti₃C₂/WO₃/PVDF membrane under visible light irradiation. This study opens possibilities to construct multi-functional and robust MXenes-based photocatalytic membrane for long-term water purification.     

Novel Ag2S/ZnS/carbon nanofiber ternary nanocomposite for highly efficient photocatalytic hydrogen production

Novel Ag₂S/ZnS/carbon nanofiber (CNF) ternary nanocomposite with high photocatalytic H₂ production performance was synthesized by combination of an in-situ solid-state process and a cation-exchange reaction, using organic–inorganic layered zinc hydroxide nanofibers as precursor. Moreover, the loading amount of Ag₂S nanocrystals can be readily regulated by changing the AgNO₃ concentration, and the optimized H₂ production rate was 224.9 μmol h^− 1, significantly higher than that of the reported ZnS-based composite photocatalysts. The synergistic effect of CNF and Ag₂S as water reduction and oxidation cocatalyst, respectively, can greatly suppress the charge recombination thus resulting in high photocatalytic H₂ production activity.     

Enhanced photocatalytic hydrogen evolution over TiO2/g-C3N4 2D heterojunction coupled with plasmon Ag nanoparticles

2D heterojunction based on g-C₃N₄ nanosheets with other semiconductor nanosheets is a promising way to improve photocatalytic hydrogen evolution (PHE) activity over g-C₃N₄. However, current 2D heterojunction based on g-C₃N₄ are unsatisfactory due to their insufficient absorption of visible light and inefficient charge separation. In this work, Ag/TiO₂/g-C₃N₄ nanocomposites based on 2D heterojunction coupling with Ag surface plasmon resonance (SPR) were synthesized by a method combining facile wetness impregnation calcination. The PHE activity of Ag/TiO₂/g-C₃N₄ nanocomposites is attributed to the TiO₂/g-C₃N₄ 2D heterojunction and bare g-C₃N₄ nanosheet under visible light irradiation, indicating a cooperative effect between Ag and TiO₂/g-C₃N₄ 2D heterojunction. As a result of SPR effect, the composites strongly absorb visible light. In addition, the oscillating hot electrons from Ag can easily transfer to 2D heterojunction. This synergistic effect lead to sufficient visible light absorption and efficient charge separation of 2D heterojunction, which improved the PHE activity of g-C₃N₄. This work indicates that loading metal nanoparticles on 2D heterojunction as metal SPR-2D heterojunction nanocomposites may be a potential method for harvesting visible light for PHE.     

Novel 0D/2D Bi2WO6/MoSSe Z-scheme heterojunction for enhanced photocatalytic degradation and photoelectrochemical activity

The catalytic activity of a single catalyst could be optimized by constructing a Z-scheme heterojunction structure with another adaptive material. 0D Bi₂WO₆ nanoparticles exhibit good oxidation ability, while 2D MoSSe nanoplates with low internal resistance show excellent reduction ability. Herein, novel 0D/2D Bi₂WO₆/MoSSe Z-scheme heterojunction catalysts (BMSS) with different Mo: Bi molar ratios were developed by combining the advantages of pure Bi₂WO₆ and MoSSe. The matched energy bands may provide the possibility to construct heterojunction, and the internal electric fields could facilitate the separation and transmission of internal carriers. Energy band structure analyses and electron spin resonance (ESR) results have further confirmed the existence of the above Z-scheme heterojunction structure and internal electric field. More importantly, as-prepared BMSS catalysts were proved to have excellent oxidation and reduction ability from photocatalytic and photoelectrochemical results. With an optimized MoSSe loading ratio of 3.66%, the BMSS3 catalyst showed 4.13 times of photocurrent density than that of pure Bi₂WO₆ and displayed an excellent degradation rate (0.0377 min^?1). It can be concluded that BMSS catalysts will have promising applications in photoelectrochemistry and photocatalysis.     

The role of graphene and europium on TiO2 performance for photocatalytic hydrogen evolution

Highly efficient Eu-TiO₂/graphene composites were synthesized by a two-step method such as sol-gel and hydrothermal process. The synthesized photocatalysts were characterized by XRD, TEM, XPS, UV–vis diffuse reflectance spectroscopy and photoluminescence (PL) spectroscopy. The results confirmed that anatase Eu-TiO₂ nanoparticles with average 10 nm sizes were successfully deposited on two-dimensional graphene sheets. The UV–visible spectroscopy showed a red shift in the absorption edge of TiO₂ due to Eu doping and graphene incorporation. Moreover, effective charge separation in Eu-TiO₂/graphene composites was confirmed by PL emission spectroscopy compared to TiO₂/graphene, Eu-TiO₂ and pure TiO₂. The photocatalytic activity for H₂ evolution over prepared composites was studied under visible light irradiation (λ ≥ 400 nm). The results demonstrate that photocatalytic performance of the photocatalysts for hydrogen production increases with increasing doping concentration of Eu upto 2 at%. However, further increase in doping content above this optimum level has decreased the performance of photocatalyst. The enhanced photocatalytic performance for H₂ evolution is attributed to extended visible light absorption, suppressed recombination of electron-hole pairs due to synergistic effects of Eu and graphene.     

A highly efficient ZnS/CdS@TiO2 photoelectrode for photogenerated cathodic protection of metals

Shell-core nanostructured ZnS/CdS quantum dots (QDs) were assembled uniformly on the surface of TiO₂ nanotube arrays by sequence chemical bath deposition (CBD) of CdS and ZnS in alcohol solution system. The morphology and chemical composition of the obtained composite thin films were characterized by scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy. The effect of solvent and immersion cycles for the photoanode preparation on the photoelectrochemical activity and photogenerated cathodic protection property was investigated. It is found that the nanostructured CdS QDs (20 cycles) coated on TiO₂ nanotube arrays show a remarkably enhanced photoelectrochemical activity. The coating of ZnS QD shells (5 cycles) is able to improve the stability of the CdS@TiO₂ photoanode under white-light irradiation. After the irradiation light is turned off, the photogenerated cathodic protection of 403 stainless steel (403SS) can be remained for several hours.     

3D/2D ZnIn2S4/BiFeO3 as S-scheme heterojunction photocatalyst for boosted visible-light hydrogen evolution

Photocatalytic H₂ evolution technique has been proved to be one of the promising approaches to overcome the present energy and environmental issues caused by the combustion of fossil fuel. Constructing heterojunction can realize the efficient separation and migration of charges and thus achieve enhanced H₂ evolution performance. Herein, we designed and prepared a ZnIn₂S₄/BiFeO₃ heterojunction photocatalyst with a 3D/2D structure via an ultrasonic self-assembly process. The typical 3D/2D structure with intimate interface was obtained, which not only provided more active sites but also boosted the migration of photogenerated charges. The optimal mass ratio of BiFeO₃ in ZnIn₂S₄/BiFeO₃ was determined to be 10%, and a 10.5-fold increase in H₂ evolution rate in comparison with of pure ZnIn₂S₄ was achieved. Furthermore, the ZnIn₂S₄/BiFeO₃ composite exhibited excellent recyclability and structural stability based on cycling experiment. A S-scheme heterojunction mechanism was revealed according to the experimental results of photocatalytic H₂ evolution and electrochemical tests.     

P-doped MoS2/Ni2P/Ti3C2Tx heterostructures for efficient hydrogen evolution reaction in alkaline media

By combining the advantages of doping to change the electronic structure of molybdenum disulfide (MoS₂), transition metal phosphides, and MXene, we proposed the idea of designing and preparing a new type of composite material, P-doped MoS₂/Ni₂P/Ti₃C₂T_x heterostructures (denoted as P@MNTC), to serve as the hydrogen evolution reaction (HER) catalyst of electrochemical water splitting. The as-prepared P@MNTC heterostructures show a significant HER activity with an overpotential of 120 mV at 10 mA cm^–2 in alkaline electrolyte, with decreasing 105 and 125 mV compared with those of MoS₂ and MXene, respectively. The density functional theory indicates that the P doping and synergy effect of Ti₃C₂T_x can enhance the activation of MoS₂ and thus promote dissociation and absorption of H₂O during HER process. This strategy provides a promising way to develop high-efficiency MoS₂- and Ti₃C₂T_x-based composite catalysts for alkaline HER.     

Facile construction Z-scheme anatase/rutile TiO2/g-C3N4 hybrid for efficient photocatalytic H2 evolution under visible-light irradiation

Z-scheme anatase/rutile TiO₂/g-C₃N₄ hybrids (denoted as LTARCN-x, x represents calcination temperature) were designed and synthesized by growing TiO₂ nanorods on the surface of g-C₃N₄ utilizing impregnation-calcination method. Furthermore, through the etched effect of hydrochloric acid and calcination treatment, the as-prepared LTARCN-x possessed abundant pore structure and larger surface area, and the surface area of LTARCN-425 was 8.5 times than that of bulk g-C₃N₄. Meanwhile, the g-C₃N₄ would play a role of carrier to prevent from the aggregation of TiO₂ nanorods. In addition, under visible light irradiation, the Z-scheme heterostructure would be constructed between the rutile TiO₂ nanorod and g-C₃N₄ nanosheet, respectively. The optimized photocatalyst LTARCN-425 exhibited a preferable activity, the photocatalytic hydrogen production rate of LTARCN-425 was about 1031 μmol g^?1 h^?1, and it was about 6.3 and 13.6 times than that of g-C₃N₄ and TiO₂, respectively. Moreover, the photocatalytic mechanism of the hydrogen production was studied intensively via designing fluorescent probe, Pt and PbO₂ deposition experiment, and the characterizations of EPR, TEM, HRTEM and XPS.     

Strain field evolution of 2D needled C/SiC composites under tension

In this study, the digital image correlation (DIC) technique was applied to the tensile test of 2D needled C/SiC composites as a full-field measuring tool with the purpose of characterizing the tensile behavior of the material. The non-linear macroscopic tensile stress-strain curve was obtained. The relationship between the local non-linearity and the macroscopic non-linearity was investigated. The spot- and band-type strain field distributions were observed, and the evolution of the non-uniform strain field distribution was studied. The correlation between the strain field distribution and the structure of the needled preform of the material was also discussed.     

Highly efficient visible/near-infrared light photocatalytic degradation of antibiotic wastewater over 3D yolk-shell ZnFe2O4 supported 0D carbon dots with up-conversion property

The development of effective visible and near-infrared photocatalysts is highly promising in the current field of photocatalysis. Herein, carbon dots/ZnFe2O4(CDs/ZFO) with coating zero dimensional(0D) CDs on the surface of three dimensional(3D) yolk-shell ZFO spheres was designed and synthesized via a selftemplated solvothermal method. The as-prepared CDs/ZFO composites displayed outstanding visible and near-infrared photocatalytic degradation activity of tetracycline(TC), and the optimal 3% CDs...     

全pH范围下MoS2/Ni3S2/NF的高效电催化析氢行为

在全pH（0~14）范围下设计开发低廉、高活性的析氢电催化剂对新能源开发和利用具有重要实际意义。通过简单的溶剂热法在镍网（NF）上原位构筑了纳米线结构MoS2/Ni3S2/NF电催化剂，该催化剂在全PH范围下表现出优异的析氢（HER）活性。电化学测试结果表明，使用41 mg四硫代钼酸铵制得的MoS2/Ni3S2/NF-41电极,在电流密度10 mA/cm2时，其在碱性（1 moL/L KOH，pH=14）、中性（0.5 moL/L PBS，pH=7）和酸性（0.5 moL/L H2SO4，pH=0）介质中HER过电位分别为87、113和195 mV，并相应表现出较低的Tafel斜率。另外，SEM、TEM、EDX、XPS等表征手段表明该催化剂具有良好的结构稳定性。本研究为过渡金属硫化物在全pH环境下高效析氢提供了新途径。     

Linker-free layer-by-layer self-assembly of gold nanoparticle multilayer films for direct electron transfer of horseradish peroxidase and H2O2 detection

Au nanoparticle (AuNP) multilayer films were fabricated by combining interfacial assembly and layer-by-layer assembly. The key point is that the procedure does not require assistance of organic linker molecules, thus providing a suitable platform for the modification of biological molecules. Direct electron transfer can easily take place between a glassy carbon electrode and horseradish peroxidase (HRP) molecules adsorbed on AuNP films. The current density of direct electron transfer was closely related to the layer number, m, and reached a maximum value for m = 4. The optimized HRP/AuNP multilayer film had a relatively rapid response and satisfactory selectivity for H₂O₂ detection. The linear range and the detection limit were 9.8 × 10⁻⁶ to 6 × 10⁻³ mol/L and ∼4.9 × 10⁻⁶ mol/L (S/N = 3), respectively.     

TiO2 NTAs decorated with thin CuBi2O4 nanosheets for efficient photocatalytic dye degradation and hydrogen generation

Photocatalytic technology is the recent investigation focus because of the wide applications in sewage disposal and new energy generation. In this paper, the optical and photocatalytic properties of TiO₂ NTAs were enhanced by the hydrothermal deposition of CuBi₂O₄ by regulating the precursor concentration. The results indicated that the precursor concentration played remarkable influences on the morphology and photocatalytic ability. The mild reagent concentration was in favor of super-thin CuBi₂O₄ nanosheet formation. CuBi₂O₄/TiO₂ NTAs with high reagent concentration exhibited high photocurrent and hydrogen production, and showed outstanding performance in the removal of organic dyes and heavy metal ions. The free radical production and the photocatalytic progress were introduced in detail. The high photocatalytic activity exhibits prospective foreground in industrial waste water treatment and novel energy resource development.     

煤基碳量子点/氮化碳复合材料制备及其光催化还原CO2性能

以太西无烟煤为原料,采用化学氧化法制备煤基碳量子点(C-CQDs),进一步以C-CQDs和尿素为前体,原位复合制备得到煤基碳量子点/氮化碳(C-CQDs/g-C₃N₄)复合材料。采用TEM、XRD、FT-IR、UV-Vis、PL等手段对样品结构性能进行了表征和分析,进而考察了其在光催化还原CO₂合成甲醇过程的催化性能。研究表明：C-CQDs均匀地负载在g-C₃N₄的表面,且掺杂适量的C-CQDs有利于提高C-CQDs/g-C₃N₄的光催化活性,当可见光照12 h时,其光催化还原CO₂甲醇产量最高可达28.69 μmol/(g cat),约为相同条件下纯石墨相g-C₃N₄作用时甲醇产量的2.2倍。