GO/Ag3PO4复合光催化剂的制备、表征及光催化性能

以石墨粉为原料,采用Hummers氧化法合成氧化石墨烯(GO).然后在超声作用下,将不同含量的Ag₃PO₄沉积在GO上,制备了一系列4% (w,质量分数) GO/Ag₃PO₄、8% GO/Ag₃PO₄、16% GO/Ag₃PO₄和32% GO/Ag₃PO₄复合光催化剂.对所制备的光催化剂运用N₂物理吸附、X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、拉曼光谱、傅里叶变换红外(FT-IR)光谱、紫外-可见漫反射吸收光谱(UV-Vis DRS)等手段进行了表征,并在可见光下考察了GO含量对Ag₃PO₄光催化降解甲基橙(MO)的性能.结果表明, GO能够和Ag₃PO₄实现均匀复合.复合GO提高了催化剂的比表面积,改善了催化剂的吸附性能.复合16% GO使Ag₃PO₄光催化活性提高最显著, 120 min内对MO的降解率达到83%,是纯Ag₃PO₄光催化活性的7.5倍. GO能提高催化剂的比表面积,促进光生电子-空穴(e^-/h⁺)的分离,产生更多活性自由基,从而提高Ag₃PO₄光催化的活性和稳定性.     

CH3O和CO在Pd(111)表面偶联反应机理的理论研究

采用DMol³程序包中的GGA-PW91方法, 结合周期平板模型, 对CH₃O和CO在Pd(111)表面的反应进行了系统研究. 计算结果表明, 吸附在Pd(111)表面顶位上的CO分子中C原子所带正电荷最多, 容易与亲核试剂反应, 化学吸附能稍低, 有利于在表面上移动发生亲电插入反应; CH₃O 在Pd(111)表面fcc穴位吸附稳定, O原子上所带的负电荷较多, 易被亲电试剂进攻. 过渡态搜索表明, Pd(111)表面顶位上的CO与fcc穴位上CH₃O反应生成CH₃OOC的为放热反应, 反应能垒较低, 有利于偶联反应的进行.     

Trichloroacetic Acid Removal by a Reductive Spherical Cellulose Adsorbent

A novel spherical cellulose adsorbent with amide and sulphinate groups was used for a first reduction of trichloroacetic acid(TCAA) and a subsequent adsorption of generated species, haloacetic acids. The removal mechanism involved TCAA reduction by sulphinate groups and the adsorption of the haloacetic acids through electrostatic interaction with amide group. Investigation of product formation and subsequent disappearance reveals that the reduction reactions proceed via sequential hydrogenolysis, and transform to acetate ultimately. Adsorption of haloacetic acids was ascertained by low chloride mass balances(89.3%) and carbon mass balances(75.1%) in solution. The pseudo-first-order rate constant for TCAA degradation was (0.93±0.12) h^-1. Batch experiments were conducted to investigate the effect of pH value on the reduction and adsorption process. The results show that the reduction of TCAA by sulphinate groups requires higher pH values while the electrostatic attraction of haloacetic acids by amino group is favorable in more acidic media.     

Imidazolium Ionic Liquids,Imidazolylidene Heterocyclic Carbenes,and Zeolitic Imidazolate Frameworks for CO2 Capture and Photochemical Reduction

Imidazolium ionic liquids (ILs), imidazolylidene N‐heterocyclic carbenes (NHCs), and zeolitic imidazolate frameworks (ZIFs) are imidazolate motifs which have been extensively investigated for CO₂ adsorption and conversion applications. Summarized in this minireview is the recent progress in the capture, activation, and photochemical reduction of CO₂ with these three imidazolate building blocks, from homogeneous molecular entities (ILs and NHCs) to heterogeneous crystalline scaffolds (ZIFs). The developments and existing shortcomings of the imidazolate motifs for their use in CO₂ utilizations is assessed, with more of focus on CO₂ photoredox catalysis. The opportunities and challenges of imidazolate scaffolds for future advancement of CO₂ photochemical conversion for artificial photosynthesis are discussed.     

Biomimetic Donor–Acceptor Motifs in Conjugated Polymers for Promoting Exciton Splitting and Charge Separation

Natural photosynthesis serves as a model for energy and chemical conversions, and motivates the search of artificial systems that mimic nature′s energy‐ and electron‐transfer chains. However, bioinspired systems often suffer from the partial or even large loss of the charge separation state, and show moderate activity owing to the fundamentally different features of the multiple compounds. Herein, a selenium and cyanamide‐functionalized heptazine‐based melon (DA‐HM) is designed as a unique bioinspired donor–acceptor (D‐A) light harvester. The combination of the photosystem and electron shuttle in a single species, with both n‐ and p‐type conductivities, and extended spectral absorption, endows DA‐HM with a high efficiency in the transfer and separation of photoexcited charge carriers, resulting in photochemical activity. This work presents a unique conjugated polymeric system that shows great potential for solar‐to‐chemical conversion by artificial photosynthesis.     

Polymeric Donor–Acceptor Heterostructures for Enhanced Photocatalytic H2 Evolution without Using Pt Cocatalysts

Polymeric carbon nitride (CN) is a promising material for photocatalytic water splitting. However, CN in its pristine form tends to show moderate activity due to fast recombination of the charge carriers. The design of efficient photocatalytic system is therefore highly desired, but it still remains a great challenge in chemistry. In this work, a pyrene-based polymer able to serve as an electron donor to accelerate the interface charge carrier transfer of CN is presented. The construction of donor-acceptor (D–A) heterojunction was confirmed to significantly restrain the charge recombination and, thus, improve the proton reduction process. This study provides a promising strategy to achieve solar H₂ production in an efficient and low-cost manner.     

Ultrasound-promoted synthesis of γ-graphyne for supercapacitor and photoelectrochemical applications

As a novel type of carbon materials, graphynes possesses the merits of high carrier mobility and large surface areas, etc. However, to date, the main research of graphynes is focused on theoretical calculation whereas few strategies have been reported for the fabrication of graphynes. In this work, a facile method named ultrasound-promoted synthesis was developed to fabricate γ-graphyne using PhBr₆ and CaC₂ as the raw materials. The reaction system in argon atmosphere ultrasonically vibrated for 24 h in the ultrasonic bath at a power of 180 W and frequency of 53 kHz. The structure, morphology, and component of the obtained samples were detected by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, FT-IR spectra, scanning electron microscopy, transmission electron microscopy, and the selected area electron diffraction. The electrochemical and photoelectrochemical measurements indicate that γ-graphyne can be used as superior electrode mateirals in supercapacitor and photoelectrochemical catalysis. From the results of galvanostatic charge/discharge measurements, the γ-graphyne supercapacitor delivers a maximum specific capacitance of 81 F/g at 0.2 A/g and a capacitance retention rate of 87.5% after 5000 cycles at 3 A/g. Moreover, UV-vis light photoelectrochemical response and high carrier density are observed for γ-graphyne. It is also demonstrated that the charge-transfer resistance is low by Tafel slopes and Nyquist plots. This work puts forward a new and facile strategy for the fabrication of γ-graphyne and explores its application in the field of solar energy conversion and storage.     

Molecular pore-wall engineering of mesozeolitic conjugated polymers for photoredox hydrogen production with visible light

A chemical protocol based on molecular engineering of polymeric matrix is developed for the chemical optimization of ordered mesoporous carbon nitride(OMCN) in this study to address the concerns on the serious nanostructure-induced semiconductive defects, in particular the remarkable hypsochromic shift of absorption threshold and the increased excition dissociation energy. Physical characterizations demonstrate that the successful incorporation of 3-aminothiophene-2-carbonitrile(ATCN) aromatic donor in OMCN matrix can efficiently extend the π-conjugated system, red-shift the optical absorption toward longer wavelengths and promote exciton splitting, thus well overcoming the serious semiconductive defects. In addition, the unique structural benefits of OMCN, such as the well-orientated nanoarchitectures with large specific surface area and uniform nanosized pore, have been well remained in ATCN-modified sample(OMCNA) via adjusting the ATCN/cyanamide molar ratio to minimize the unavoidable matrix disturbance. Hence, an obviously enhanced photocatalytic activity toward H_2 evolution and selective oxidation of alcohols are obtained on optimized OMCNA samples, greatly underlining the advantage of molecular engineering in supporting nanostructured photocatalysts.     

Dopamine-loaded Liposomes-amplified Electrochemical Immunoassay Based on MXene (Ti3C2)−AuNPs

A simple and novel electrochemical immunoassay based on MXene (Ti₃C₂)−Au nanoparticles (AuNPs) was designed for sensitive screening of a disease-related biomarker, prostate-specific antigen (PSA), by using dopamine-loaded liposomes (DLL) for signal amplification. The system involves two parts, namely, sandwich-type immunoreaction to capture DLL and electrochemical measurement of dopamine. The target PSA can cause a specific antigen-antibody reaction and DLL are enriched in the enzyme-labeled pores. After Triton X-100 is injected into the detection cell, the carried DLL was quickly cracked to release dopamine wrapped in the cavity. A nanocomposite consisting of MXene (Ti₃C₂) support to immobilize Au nanoparticles (Ti₃C₂−Au) was utilized to modify a glassy carbon electrode, which gives a strongly enhanced differential pulse voltammetric (DPV) signals for dopamine. In this case, the change of DPV signal depends on the amount of dopamine released by liposomes, which is further positively correlated with the concentration of the analyte PSA. Combining the of MXene (Ti₃C₂)−AuNPs nanomaterials (large specific surface area, excellent electrical conductivity, and good electrocatalytic properties) with the liposome signal amplification strategy, the electrochemical immunoassay exhibited excellent performance toward PSA determination with a broad linear range of 1 pg/mL to 50 ng/mL and limit of detection down to 0.31 pg/mL (S/N=3) under the optimized testing conditions. High specificity for PSA over other disease-related biomarkers and acceptable nanocomposite/electrode stability were acquired. The excellent analytical performance shows that the current strategy provides an effective detection platform for clinical sample analysis.