Regulation on polymerization degree and surface feature in graphitic carbon nitride towards efficient photocatalytic H2 evolution under visible-light irradiation

A kind of graphitic carbon nitride(TSC-550)with high polymerization degree and improved surface property was prepared by a new precursor of thiosemicarbazide.Th...     

Effect of TiO2 support on immobilization of cobalt porphyrin for electrochemical CO2 reduction

Electrochemical reduction of CO2 is a promising strategy to manage the global carbon balance by trans-forming CO2 into chemicals.The efficiency of CO2 electroreduction is largely dependent on the design of hybrid electrode where both support and catalyst govern the performance of the electrolyzer.In this work,TiO2 calcined at different temperatures,was used as a support for immobilization of cobalt tetraphenyl porphyrin (CoTPP) and its effect on CO2 reduction was studied.It is demonstrated that the crystalline phase of TiO2 and doping of TiO2 apparently affecting CO2 electroreduction.It is found that anatase phase exhibits higher activity and selectivity compared to futile due to the enhanced conductivity which in turn enables faster electron transfer between the support and CoTPP.As for dopants,the carbon dop-ing in anatase TiO2 is proven to further enhance its conductivity,consequently resulting in the enhanced performance.This study implies that the rational design of supports is important for the performance of the hybrid electrode towards electrochemical CO2 reduction.     

Chlorine doped graphitic carbon nitride nanorings as an efficient photoresponsive catalyst for water oxidation and organic decomposition

Rationally engineering the microstructure and electronic structure of catalysts to induce high activity for versatile applications remains a challenge. Herein, chlorine doped graphitic carbon nitride (Cl-doped g-C₃N₄) nanorings have been designed as a superior photocatalyst for pollutant degradation and oxygen evolution reaction (OER). Remarkably, Cl-doped g-C₃N₄ nanorings display enhanced OER performance with a small overpotential of approximately 290 mV at current density of 10 mA cm⁻² and Tafel slope of 83 mV dec^-1, possessing comparable OER activity to precious metal oxides RuO₂ and IrO₂/C. The excellent catalytic performance of Cl-doped g-C₃N₄ nanorings originates from the strong oxidation capability, abundant active sites exposed and efficient charge transfer. More importantly, visible light irradiation gives rise to a prominent improvement of the OER performance, reducing the OER overpotential and Tafel slope by 140 mV and 28 mV dec^-1, respectively, demonstrating the striking photo-responsive OER activity of Cl-doped g-C₃N₄ nanorings. The great photo-induced improvement in OER activity would be related to the efficient charge transfer and the OH radicals arising spontaneously on CN-Cl₁₀₀ catalyst upon light irradiation. This work establishes Cl-doped g-C₃N₄ nanorings as a highly competitive metal-free candidate for photoelectrochemical energy conversion and environmental cleaning application.     

An efficient bicomponent TiO2/SnO2 nanofiber photocatalyst fabricated by electrospinning with a side-by-side dual spinneret method

In this communication, we demonstrate that the electrospinning process with a side-by-side dual spinneret can be a simple approach for fabricating bicomponent TiO2/SnO2 nanofibers with controllable heterojunctions. Specifically, both of the TiO2 and SnO2 components in the nanofibers are fully exposed to the surface. This morphology fully utilized the photogenerated holes and electrons during the photocatalytic process, thus leading to a high photocatalytic activity. We believe that this versatile approach can be extended to fabricate other novel high-efficiency bicomponent photocatalysts.     

Synthesis of graphitic carbon nitride by reaction of melamine and uric acid

Graphitic carbon nitrides were synthesized starting from melamine and uric acid. Uric acid was chosen because it thermally decomposes, and reacts with melamine by condensation at temperatures in the range of 400–600 °C. The reagents were mixed with alumina and subsequently the samples were treated in an oven under nitrogen flux. Alumina favored the deposition of the graphitic carbon nitrides layers on the exposed surface. This method can be assimilated to an in situ chemical vapor deposition (CVD). Infrared (IR) spectra, as well as X-ray diffraction (XRD) patterns, are in accordance with the formation of a graphitic carbon nitride with a structure based on heptazine blocks. These carbon nitrides exhibit poor crystallinity and a nanometric texture, as shown by transmission electron microscopy (TEM) analysis. The thermal degradation of the graphitic carbon nitride occurs through cyano group formation, and involves the bridging tertiary nitrogen and the bonded carbon, which belongs to the heptazine ring, causing the ring opening and the consequent network destruction as inferred by connecting the IR and X-ray photoelectron spectroscopy (XPS) results. This seems to be an easy and promising route to synthesize graphitic carbon nitrides. Our final material is a composite made of an alumina core covered by carbon nitride layers.     

Nanoarchitectonics of chlorophyll and Mg co-modified hierarchical BiOCl microsphere as an efficient photocatalyst for CO2 reduction and ciprofloxacin degradation

It is of great significance to develop an efficient photocatalyst through simple methods for solar energy conversion and environmental pollution treatment. In this research, chlorophyll (Chl) and Mg co-modified hierarchical BiOCl microsphere photocatalyst with high performance was synthesized using a simple low temperature wet-chemical method. The synthesized photocatalyst with the optimal content of Chl and Mg showed superior photocatalytic performance for CO₂ reduction, where the maximum yield of methanol was 100.2 µmol/(h·g_cat), which was about three times superior than that of pure BiOCl. Besides, the Chl-Mg/BiOCl also showed high performance (93.7%) for degradation of ciprofloxacin (CIP, a kind of antibiotic). Various characterization techniques were applied to determine the structure and evaluate the origin of the improved performance of Chl-Mg/BiOCl. Meanwhile, a possible mechanism for the excellent photocatalytic performance of Chl-Mg/BiOCl was proposed. Notably, Chl on the surface of BiOCl can lead to the formation of singlet state of Chl-Mg* after absorbing light and act as an electron donor which can enhance the stability and activity of the photocatalyst. What’s more, Mg not only acts as an electron capture site to inhibit the photogenerated carrier recombination, but also forms a complex with Chl to improve the stability of catalyst. This study would represent a promising candidate organic–inorganic hybrid photocatalyst for solar energy conversion and antibiotic pollution treatment.     

具有近红外吸收的二维/三维ZnIn2S4/氮掺杂石墨烯光催化剂的制备及其高效CO2捕获和光催化还原性能（英文）

具有宽光谱太阳能利用的分等级异质结光催化剂,正成为一种新兴的先进光催化材料,被应用于太阳能驱动二氧化碳转化为高附加值的化学原料.本工作通过水热法使二维硫化铟锌纳米墙垂直生长于三维氮掺杂石墨烯泡沫上,形成分等级异质结光催化剂.该催化剂展现出优异的光热转换效率、选择性捕获CO2和光催化还原CO2的能力.在273 K和1个大气压条件下,负载1 wt%氮掺杂石墨烯泡沫的复合催化剂表现出最优异的性能,其中对CO2和N2的吸附选择性为30.1,并且对CO2的等量吸附热为48.2 kJ mol^-1.在无助催化剂和牺牲剂的条件下,负载1 wt%氮掺杂石墨烯泡沫的复合催化剂,其光催化转化CO2为CH4、CO和CH3OH的效率分别是纯的硫化铟锌的9.1、3.5和5.9倍.该增强效应得益于三维石墨烯泡沫高度开放的网状结构,良好的CO2吸附能力和两种组份之间的强相互作用.此外,利用原位照射X射线光电子能谱仪和开尔文探针技术分析了电荷转移的方向,本工作为设计高效太阳能转化分等级异质结光催化剂开辟了新的思路.     

Coordination engineering of cobalt phthalocyanine by functionalized carbon nanotube for efficient and highly stable carbon dioxide reduction at high current density

Coordination engineering can enhance the activity and stability of the catalyst in heterogeneous catalysis.However,the axial coordination engineering between di...     

Preparation of 2D graphitic carbon nitride nanosheets by a green exfoliation approach and the enhanced photocatalytic performance

In this paper, we reported a new and environment-friendly strategy to exfoliate graphitic carbon nitride (CN) in hot water to obtain ultrathin CN nanosheets (CNNS). By thermal treating, water molecules were intercalated into the interlayer space of bulky CN and further hydrolyzed the bridge-linked N groups between tri-s-triazine units, thereby cutting the CN layers into CNNS. Due to the negative charges on surface (Zeta potential was ?13 mV at pH 7), the CNNS colloids were extremely stable. The physicochemical characterization indicated that the as-prepared CNNS had a typical 2D morphology with a ~1.2 nm thickness and numerous –OH groups on surface. Moreover, the high charge separation and transport ability were achieved in CNNS because of the retaining of conjugated CN system. Compared to the bulk CN, the as-prepared ultrathin CNNS exhibited an enhanced photocatalytic performance (four times higher than that of the bulk CN) for degradation of organic dye under visible light irradiation. Additionally, the superior reusability and the excellent generality of CNNS for decomposing other pollutants were also demonstrated. Finally, we proposed a possible mechanism of CNNS based on the examined band structure and the main active species determined by quenching of various active species.     

Stable and fast oil recovery by environmentally friendly and easy to synthesize pristine graphitic carbon nitride

Clean Technologies and Environmental Policy - Fast oil recovery from the ocean after an oil spill is crucial before permanent damage happens to the ecological balance and marine life. Sorbents that...     

Improved visible-light driven photocatalysis by loading Au onto C3N4 nanorods for degradation of RhB and reduction of CO2

In this work, a solution-assembly technique was adopted to compose the g-C₃N₄ (CN) nanorods (CN1, CN2 and CN3) with a desired microstructure. Subsequently, different amounts of Au nanoparticles (NPs) with sizes ~10 nm were loaded on CN2 nanorods by an in-site reduction approach, thereby a series of plasmonic photocatalyst (CN2-A1, CN2-A2 and CN2-A3) were fabricated. The activities were investigated by photodegrading Rhodamine B (RhB) and photoreducing CO₂ into CO with the irradiation of visible light, respectively. And the degradation rates of RhB over CN2-A2 photocatalyst were 97.28% in 80 min, which was 1.45 times higher than that of pure CN2 (66.90%). Moreover, without any sacrificial agents, the reduction yields of CO₂ into CO by CN2-A2 photocatalyst was 3.11 μmol/g in 4 h, that was 2.46 times higher than that of CN2 (1.26 μmol/g). The improved photocatalytic performance was owning to the stronger localized surface plasmon resonance (LSPR) effect, which not only increased the utilization efficiency of visible light, but also sped up the formation and separation of photo-induced carriers. In addition, a potential charge transfer mechanism was tentatively proposed on account of as-obtained test dates.     

Porous graphitic carbon nitride with lamellar structure: Facile synthesis via in-site supramolecular self-assembly in alkaline solutions and superior photocatalytic activity

The development of highly active photocatalysts is the primary goal in the field of photocatalysis. We herein first develop a facile and scale up approach to synthesize porous polymeric graphitic carbon nitride (g-C₃N₄) with lamellar structure through thermal polycondensation of supramolecular aggregates. The feature of this approach lies in the directed in-situ self-assembly of cyanuric acid molecules, converted from the hydrolysis of melamine in NaOH solution, with the residual melamine molecules to form supramolecular aggregates, which lead to the formation of porous g-C₃N₄ with lamellar structure. The synthesized lamellar g-C₃N₄ exhibit superior photocatalytic activity as demonstrated by the complete degradation of methylene blue (MB) under one hour’s visible light irradiation, as well as excellent stability with high activity retained after four runs of MB degradation testing. The enhancement in photocatalytic performance can be attributed to its unique lamellar structure with high surface area, narrow bandgap, and efficient separation of photogenerated electron-hole pairs. This work shows that the alkaline solutions can be used as the molecular self-assembly medium and opens a new avenue towards designing highly active g-C₃N₄-based photocatalyts for energy and environmental applications.     

Synthesis of cuprous oxide nanoparticles on graphitic carbon nitride and reduced graphene oxide and their catalytic performance toward the reduction of 4-nitrophenol

In this work, a desired Cu₂O catalyst supported on graphitic carbon nitride and reduced graphene oxide hybrid (Cu₂O/g-C₃N₄–rGO) with excellent catalytic performance in the reduction of 4-nitrophenol (4-NP) by NaBH₄ has been fabricated. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), N₂ adsorption/desorption and Fourier-transform infrared (FTIR) techniques as well as catalytic test using the reduction of 4-NP by NaBH₄ as probe reaction have been used to investigate the structure–properties relationship of the as-prepared Cu₂O/g-C₃N₄–rGO composites. The results demonstrate that ultrafine Cu₂O nanoparticles can be stably anchored on g-C₃N₄–rGO hybrid by tuning the initial ratio of rGO (reduced graphene oxide) to g-C₃N₄, where homogeneous dispersion of g-C₃N₄ on sheet-like rGO plays a very important role in confining the ultrafine Cu₂O nanoparticles and excellent catalytic performance is noticed on Cu₂O/g-C₃N₄–rGO composite for the reduction of 4-NP by NaBH₄ with an activity parameter up to 6330 s^-1g^-1.

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Facile synthesis of flower-like CQDs/S-Bi4O5Br2 composites as a highly efficient visible-light response photocatalyst for ciprofloxacin degradation

Journal of Materials Science - The flower-like CQDs/S-Bi4O5Br2 composites photocatalyst with high visible-light response is prepared by adjusting bismuth-rich, S-doped, and introducing carbon...     

Acid-induced topological morphology modulation of graphitic carbon nitride homojunctions as advanced metal-free catalysts for OER and pollutant degradation

Topological morphology that dominates the surface electronic properties of nanostructures plays a key role in producing desired materials for versatile functions and applications in many fields,but its modula-tion for specific functions remains a big challenge.Herein,we report an acid-induced method to prepare S-doped graphitic carbon nitride/graphitic carbon nitride(S-CN/CN)homojunction by simply pyrolyzing a supramolecular precursor synthesized from melamine and H2SO4.The topological morphology and electronic structure of CN homojunction can be easily adjusted only by changing the ratio of raw materi-als.Moreover,the topological morphology of S-CN/CN homojunction can be further adjusted from hollow cocoon to 2D nanosheets by changing the annealing conditions.The optimized S-CN/CN homojunction shows highly efficient in charge transfer and separation and exhibits superior OER activity and high abil-ity to degrade organic pollutants.Impressively,S-CN/CN nanosheets only demand low overpotential of 301 mV to drive a current density of 10 mAcm-2 in 1 M KOH media,and the corresponding Tafel slope is only 57.71 mV/dec,which is superior to the most advanced precious metal IrO2 catalyst.Moreover,under visible light irradiation,its photodegradation kinetic rate of RhB is 2.38,which is 47.6 times higher than that of bulk CN.This work provides useful guidance for designing and developing efficient multifunctional metal-free catalysts.     

Synthesis of band gap-tunable alkali metal modified graphitic carbon nitride with outstanding photocatalytic H2O2 production ability via molten salt method

Band gap-tunable alkali metal modified graphitic carbon nitride was prepared by a molten salt method. X-ray diffraction, N₂ isothermal sorption, ultraviolet-visible spectroscopy, scanning electron microscope, X-ray photoelectron spectroscopy and photoluminescence were used to characterize the obtained catalysts. The photocatalytic H₂O₂ production ability of as-prepared catalyst was investigated. The results indicate that K⁺ and Na⁺ are doped into g-C₃N₄ lattice simultaneously by the molten salt method. Alkali metal modification not only promotes the specific surface area, visible light absorption and separation of electron-hole pairs, but tunes the conduction band and valence band edge positions of as-prepared catalysts by controlling the weight ratio of eutectic salts to melamine. The tunable band edge positions result in the photocatalytic H₂O₂ production from “single channel pathway” to “two channel pathway”, leading to the promoted H₂O₂ production ability.     

A 3D/0D cobalt-embedded nitrogen-doped porous carbon/supramolecular porphyrin magnetic-separation photocatalyst with highly efficient pollutant degradation and water oxidation performance

A 3D/0D cobalt-embedded nitrogen-doped porous carbon nanocubes(Co-N-C)/supramolecular tetra(4-carboxylphenyl) porphyrin nanocrystals(SA-TCPP) photocatalyst was successfully self-assembled via π –πinteraction, hydrogen bonding, and chemical bonding. Co-N-C/SA-TCPP heterostructure exhibited satisfactory visible photocatalytic oxidation performance on pollutant degradation and water evolution. The degradation rates of Co-N-C/ST(30%) composite towards 2,4-dichlorophenol, ofloxacin, and ethylene were...     

Rod and spherical silica microlenses fabricated by CO2 laser melting

The fabrication and testing of glass microlenses with rod and spherical shapes are described. The sizes of the lenses range from tens of micrometers to several millimeters. The surfaces of the lenses were fabricated by the melting method. These surfaces have been studied by several methods. The theoretical behavior of the lenses was investigated by ray tracing. Some applications of the lenses are presented.