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1.
Spontaneously solar‐driven water splitting to produce H2 and O2, that is, the conversion of solar energy to chemical energy is a dream of mankind. However, it is difficult to make overall water splitting feasible without using any sacrificial agents and external bias. Drawing inspiration from nature, a new artificial Z‐scheme photocatalytic system has been designed herein based on the two‐dimensional (2D) heterostructure of black phosphorus (BP)/bismuth vanadate (BiVO4). An effective charge separation makes possible the reduction and oxidation of water on BP and BiVO4, respectively. The optimum H2 and O2 production rates on BP/BiVO4 were approximately 160 and 102 μmol g?1 h?1 under irradiation of light with a wavelength longer than 420 nm, without using any sacrificial agents or external bias.  相似文献   

2.
Using a mixture of NO + O2 as the oxidant enabled the direct selective oxidation of methane to dimethyl ether (DME) over Pt/Y2O3. The reaction was carried out in a fixed bed reactor at 0.1 MPa over a temperature range of 275–375 °C. During the activity tests, the only carbon‐containing products were DME and CO2. The DME productivity (μmol gcat?1 h?1) was comparable to oxygenate productivities reported in the literature for strong oxidants (N2O, H2O2, O3). The NO + O2 mixture formed NO2, which acted as the oxygen atom carrier for the ultimate oxidant O2. During the methane partial oxidation reaction, NO and NO2 were not reduced to N2. In situ FTIR showed the formation of surface nitrate species, which are considered to be key intermediate species for the selective oxidation.  相似文献   

3.
A strategy to covalently connect crystalline covalent organic frameworks (COFs) with semiconductors to create stable organic–inorganic Z‐scheme heterojunctions for artificial photosynthesis is presented. A series of COF–semiconductor Z‐scheme photocatalysts combining water‐oxidation semiconductors (TiO2, Bi2WO6, and α‐Fe2O3) with CO2 reduction COFs (COF‐316/318) was synthesized and exhibited high photocatalytic CO2‐to‐CO conversion efficiencies (up to 69.67 μmol g?1 h?1), with H2O as the electron donor in the gas–solid CO2 reduction, without additional photosensitizers and sacrificial agents. This is the first report of covalently bonded COF/inorganic‐semiconductor systems utilizing the Z‐scheme applied for artificial photosynthesis. Experiments and calculations confirmed efficient semiconductor‐to‐COF electron transfer by covalent coupling, resulting in electron accumulation in the cyano/pyridine moieties of the COF for CO2 reduction and holes in the semiconductor for H2O oxidation, thus mimicking natural photosynthesis.  相似文献   

4.
《中国化学快报》2022,33(12):5200-5207
The matched energy band structure and efficient carrier separation efficiency are the keys to heterogeneous photocatalytic reactions. A novel organic/inorganic step scheme (S-scheme) heterojunction PDI-Urea/BiOBr composite photocatalyst was constructed by simple solvothermal reaction combined with in-situ growth strategy. The composite photocatalyst not only has high chemical stability, but also can generate and accumulate a large number of active species (h+, ?O2?, ?OH, H2O2). PDI-Urea/BiOBr showed higher photocatalytic activity for the degradation of antibiotic such as ofloxacin (OFLO), tetracycline (TC) and the production of H2O2 in the spectral range of 400–800 nm. The apparent rate constant of 15% PDI-Urea/BiOBr for photocatalytic degradation of TC (or OFLO) was 2.7 (or 2.5) times that of pure BiOBr and 1.7 (or 1.8) times that of pure PDI-Urea. The H2O2 evolution rate of 15% PDI-Urea/BiOBr was 2.5 times that of PDI-Urea and 1.5 times that of BiOBr, respectively. This work has formed a mature S-scheme heterojunction design thought and method, which offers new visions for the development of heterogeneous photocatalysts.  相似文献   

5.
《中国化学快报》2022,33(8):3792-3796
Water pollution has become a serious problem owing to the development of society. Photocatalysis is a promising approach to remove various pollutants in water, such as organic pollutants and antibiotic resistance bacteria. Meanwhile, the design of heterojunction between two semiconductors is an effective path to improve photocatalytic properties due to its potential in improving separation and transfer of photoinduced carriers. In this study, Nb2O5/g-C3N4 (NO/CN) composite materials were prepared through a one-step heating method. Characterizations confirmed successful preparation of NO/CN heterojunction structure and better optical properties than pure g-C3N4 and Nb2O5. NO/CN composite materials showed excellent photocatalytic efficiency for Escherichia coli (E. coli) inactivation (95%) compared with the pure Nb2O5 (10%) and g-C3N4 (77%). Meanwhile, NO/CN exhibited better organic pollutants removal (RhB for 94%, methyl orange (MO) for 15% and methylene blue (MB) for 87%) under visible light, which is likely owing to the heterojunction structure between g-C3N4 and Nb2O5 that leads to the good separation of photogenerated electron-hole pair. Free radical scavenging and electron spin resonance (ESR) experiments demonstrated that superoxide radicals (?O2?) and holes (h+) were the dominant radicals. Therefore, the NO/CN was proposed to be a promising material for effective disinfection and removal of organic contaminants in water treatment.  相似文献   

6.
采用溶胶凝胶法制备了多壁碳纳米管负载TiO2 (MWCNTs/TiO2),并利用透射电镜、X射线光电子能谱、X射线衍射和紫外-可见漫反射光谱对样品进行了表征。结果表明,MWCNTs/TiO2晶型以锐钛矿为主,MWCNTs的引入会限制TiO2晶粒的生长。另外,MWCNTs/TiO2的光吸收边向长波区域偏移。针对模拟烟气,在固定床光催化反应器中对采用涂覆处理的MWCNTs/TiO2的光催化脱硝性能进行了实验研究。结果表明,NO初始浓度较低时,光催化脱硝效率较高,SO2的存在可抑制光催化脱硝过程,而O2及H2O则有促进作用。在最佳实验条件(73 mg/m3 NO,8% O2,5% H2O)下,光催化脱硝效率可达46%。提出了光催化脱硝反应机理。  相似文献   

7.
通过焙烧-超声混合法成功地制备了BiOBr/g-C3N4S型异质结复合光催化剂。采用多种表征手段对样品物理属性进行了表征,包括X射线多晶粉末衍射仪(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、紫外可见漫反射光谱(UV-Vis DRS)。研究了所制备样品有/无Fe3+的光-自芬顿催化/光催化降解罗丹明B(RhB)性能。通过捕获实验确定了光催化反应中的主要活性物种,提出了光-自芬顿反应的降解机理。研究结果表明,BiOBr/g-C3N4S型异质结能原位生成H2O2,添加Fe3+后,H2O2被原位活化成活性物种且光生电流和载流子分离效率获得显著提高。该光-自芬顿过程能高效降解RhB,其反应速率常数为0.208 min-1,约为无Fe3+光催化反应速率常数的5.3倍,在光-自芬顿循环使用过程中表现出良好的稳定性。Fe...  相似文献   

8.
通过焙烧-超声混合法成功地制备了BiOBr/g-C3N4 S型异质结复合光催化剂。采用多种表征手段对样品物理属性进行了表征,包括X射线多晶粉末衍射仪(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、紫外可见漫反射光谱(UV-VisDRS)。研究了所制备样品有/无Fe3+的光-自芬顿催化/光催化降解罗丹明B (RhB)性能。通过捕获实验确定了光催化反应中的主要活性物种,提出了光-自芬顿反应的降解机理。研究结果表明,BiOBr/g-C3N4 S型异质结能原位生成H2O2,添加Fe3+后,H2O2被原位活化成活性物种且光生电流和载流子分离效率获得显著提高。该光-自芬顿过程能高效降解RhB,其反应速率常数为0.208 min-1,约为无Fe3+光催化反应速率常数的5.3倍,在光-自芬顿循环使用过程中表现出良好的稳定性。Fe3+的加入促进了光生电荷的分离和H2O2的活化,超氧阴离子自由基(·O2-)、空穴和羟基是光-自芬顿催化过程中的主要活性物种,且·O2-作用更大。  相似文献   

9.
An experimental study on the conversion of NO in the NO/N2, NO/O2/N2, NO/C2H4/N2 and NO/C2H4/O2/N2 systems has been carried out using dielectric barrier discharge (DBD) plasmas at atmospheric pressure. In the NO/N2 system, NO decomposition to N2 and O2 is the dominating reaction; NO conversion to NO2 is less significant. O2 produced from NO decomposition was detected by an on-line mass spectrometer. With the increase of NO initial concentration, the concentration of O2 produced decreases at 298 K, but slightly increases at 523 K. In the NO/O2/N2 system, NO is mainly oxidized to NO2, but NO conversion becomes very low at 523 K and over 1.6% of O2. In the NO/C2H4/N2 system, NO is reduced to N2 with about the same NO conversion as that in the NO/N2 system but without NO2 formation. In the NO/C2H4/O2/N2 system, the oxidation of NO to NO2 is dramatically promoted. At 523 K, with the increase of the energy density, NO conversion increases rapidly first, and then almost stabilizes at 93–91% of NO conversion with 61–55% of NO2 selectivity in the energy density range of 317–550 J L−1. It finally decreases gradually at high energy density. A negligible amount of N2O is formed in the above four systems. Of the four systems studied, NO conversion and NO2 selectivity of the NO/C2H4/O2/N2 system are the highest, and NO/O2/C2H4/N2 system has the lowest electrical energy consumption per NO molecule converted.  相似文献   

10.
Photoconversion of CO2 and H2O into ethanol is an ideal strategy to achieve carbon neutrality. However, the production of ethanol with high activity and selectivity is challenging owing to the less efficient reduction half-reaction involving multi-step proton-coupled electron transfer (PCET), a slow C−C coupling process, and sluggish water oxidation half-reaction. Herein, a two-dimensional/two-dimensional (2D/2D) S-scheme heterojunction consisting of black phosphorus and Bi2WO6 (BP/BWO) was constructed for photocatalytic CO2 reduction coupling with benzylamine (BA) oxidation. The as-prepared BP/BWO catalyst exhibits a superior photocatalytic performance toward CO2 reduction, with a yield of 61.3 μmol g−1 h−1 for ethanol (selectivity of 91 %).In situ spectroscopic studies and theoretical calculations reveal that S-scheme heterojunction can effectively promote photogenerated carrier separation via the Bi−O−P bridge to accelerate the PCET process. Meanwhile, electron-rich BP acts as the active site and plays a vital role in the process of C−C coupling. In addition, the substitution of BA oxidation for H2O oxidation can further enhance the photocatalytic performance of CO2 reduction to C2H5OH. This work opens a new horizon for exploring novel heterogeneous photocatalysts in CO2 photoconversion to C2H5OH based on cooperative photoredox systems.  相似文献   

11.
Heterojunction design in a two-dimensional (2D) fashion has been deemed beneficial for improving the photocatalytic activity of g-C3N4 because of the promoted interfacial charge transfer, yet still facing challenges. Herein, we construct a novel 2D/2D Cu3P nanosheet/P-doped g-C3N4 (PCN) nanosheet heterojunction photocatalyst (PCN/Cu3P) through a simple in-situ phosphorization treatment of 2D/2D CuS/g-C3N4 composite for photocatalytic H2 evolution. We demonstrate that the 2D lamellar structure of both CuS and g-C3N4 could be well reserved in the phosphorization process, while CuS and g-C3N4 in-situ transformed into Cu3P and PCN, respectively, leading to the formation of PCN/Cu3P tight 2D/2D heterojunction. Owing to the large contact area provided by intimate face-to-face 2D/2D structure, the PCN/Cu3P photocatalyst exhibits significantly enhanced charge separation efficiency, thus achieving a boosted visible-light-driven photocatalytic behavior. The highest rate for H2 evolution reaches 5.12 μmol·h–1, nearly 24 times and 368 times higher than that of pristine PCN and g-C3N4, respectively. This work represents an excellent example in elaborately constructing g-C3N4-based 2D/2D heterostructure and could be extended to other photocatalyst/co-catalyst system.   相似文献   

12.
Metal‐organic frameworks (MOFs)‐based membranes have shown great potentials as applications in gas separation. In this work, a uniform membrane based on 2D MOF Ni3(HITP)2 (HITP=2,3,6,7,10,11‐hexaaminotriphenylene) was fabricated on ordered macroporous AAO via the filtration method. To fabricate the membrane, we obtained the Ni3(HITP)2 nanosheets as building blocks via a soft‐physical exfoliation method successfully that were confirmed by AFM and TEM. We also studied the H2, CO2 and N2 adsorption isotherms of Ni3(HITP)2 powder at room temperature, which shows Ni3(HITP)2 has high heats of adsorption for CO2 and high selectivity of CO2 over N2. Gas permeation tests indicate that the Ni3(HITP)2 membrane shows high permeance and selectivity of CO2 over N2, as well as good selectivity of H2 over N2. The ideal separation factors of CO2/N2 and H2/N2 from sing‐gas permeances are 13.6 and 7.8 respectively, with CO2 permeance of 3.15×10?6 mol?m?2?s?1?Pa?1. The membrane also showed good stability, durability and reproducibility, which are of potential interest for practical applications in the CO2 separations.  相似文献   

13.
Release of the distinct NO redox‐interrelated forms (NO+, .NO, and HNO/NO?), derived from reaction of the dinitrosyl iron complex (DNIC) [(NO)2Fe(C12H8N)2]? ( 1 ) (C12H8N=carbazolate) and the substitution ligands (S2CNMe2)2, [SC6H4o‐NHC(O)(C5H4N)]2 ((PyPepS)2), and P(C6H3‐3‐SiMe3‐2‐SH)3 ([P(SH)3]), respectively, was demonstrated. In contrast to the reaction of (PyPepS)2 and DNIC 1 in a 1:1 stoichiometry that induces the release of an NO radical and the formation of complex [PPN][Fe(PyPepS)2] ( 4 ), the incoming substitution ligand (S2CNMe2)2 triggered the transformation of DNIC 1 into complex [(NO)Fe(S2CNMe2)2] ( 2 ) along with N‐nitrosocarbazole ( 3 ). The subsequent nitrosation of N‐acetylpenicillamine (NAP) by N‐nitrosocarbazole ( 3 ) to produce S‐nitroso‐N‐acetylpenicillamine (SNAP) may signify the possible formation pathway of S‐nitrosothiols from DNICs by means of transnitrosation of N‐nitrosamines. Protonation of DNIC 1 by [P(SH)3] triggers the release of HNO and the generation of complex [PPN][Fe(NO)P(C6H3‐3‐SiMe3‐2‐S)3] ( 5 ). In a similar fashion, the nucleophilic attack of the chelating ligand P(C6H3‐3‐SiMe3‐2‐SNa)3 ([P(SNa)3]) on DNIC 1 resulted in the direct release of [NO]? captured by [(15NO)Fe(SPh)3]?, thus leading to [(15NO)(14NO)Fe(SPh)2]?. These results illustrate one aspect of how the incoming substitution ligands ((S2CNMe2)2 vs. (PyPepS)2 vs. [P(SH)3]/[P(SNa)3]) in cooperation with the carbazolate‐coordinated ligands of DNIC 1 function to control the release of NO+, .NO, or [NO]? from DNIC 1 upon reaction of complex 1 and the substitution ligands. Also, these results signify that DNICs may act as an intermediary of NO in the redox signaling processes by providing the distinct redox‐interrelated forms of NO to interact with different NO‐responsive targets in biological systems.  相似文献   

14.
Exploring noble‐metal‐free, highly active and durable catalysts is vital to get to grips with the energy and environmental issues. Herein, we first dexterously design and synthesize a class of ternary Nb6/CZS/g‐CN photocatalysts for the removal of hexavalent chromium Cr (VI) and organic dye pollutant (MO) from wastewater under visible‐light irradiation. A heterojunction Nb6–1/CZS/g‐CN loaded with 0.01 g K7HNb6O19 showed excellent photocatalytic performance, with the MO photodegradation efficiency of 94% in 1 h and the Cr (VI) (150 mg/l) photoreduction efficiency as high as 91% in 2 hr. The main active species were deemed to be O2.‐. Additionally, the as‐prepared ternary heterojunction exhibits superior hydrogen evolution reaction (HER) rate. A heterojunction Nb6–4/CZS/g‐CN loaded with 0.5 g K7HNb6O19 exhibited the highest H2 evolution rate as high as 1777.86 μmol h?1 g?1 under visible‐light illumination, which is increased to 5.7 and 2.7 times that of bare CZS and biphase heterojunction CZS/g‐CN. These findings afford a new class of promising low‐cost photocatalyst bodying for its huge potential value in sustainable energy development and wastewater treatment.  相似文献   

15.
Flow reactor experiments were performed over wide ranges of pressure (0.5–14.0 atm) and temperature (750–1100 K) to study H2/O2 and CO/H2O/O2 kinetics in the presence of trace quantities of NO and NO2. The promoting and inhibiting effects of NO reported previously at near atmospheric pressures extend throughout the range of pressures explored in the present study. At conditions where the recombination reaction H + O2 (+M) = HO2 (+M) is favored over the competing branching reaction, low concentrations of NO promote H2 and CO oxidation by converting HO2 to OH. In high concentrations, NO can also inhibit oxidative processes by catalyzing the recombination of radicals. The experimental data show that the overall effects of NO addition on fuel consumption and conversion of NO to NO2 depend strongly on pressure and stoichiometry. The addition of NO2 was also found to promote H2 and CO oxidation but only at conditions where the reacting mixture first promoted the conversion of NO2 to NO. Experimentally measured profiles of H2, CO, CO2, NO, NO2, O2, H2O, and temperature were used to constrain the development of a detailed kinetic mechanism consistent with the previously studied H2/O2, CO/H2O/O2, H2/NO2, and CO/H2O/N2O systems. Model predictions generated using the reaction mechanism presented here are in good agreement with the experimental data over the entire range of conditions explored. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 705–724, 1999  相似文献   

16.
(n)MnOx–(1?n)CeO2 binary oxides have been studied for the sorptive NO removal and subsequent reduction of NOx sorbed to N2 at low temperatures (≤150 °C). The solid solution with a fluorite-type structure was found to be effective for oxidative NO adsorption, which yielded nitrate (NO? 3) and/or nitrite (NO? 2) species on the surface depending on temperature, O2 concentration in the gas feed, and composition of the binary oxide (n). A surface reaction model was derived on the basis of XPS, TPD, and DRIFTS analyses. Redox of Mn accompanied by simultaneous oxygen equilibration between the surface and the gas phase promoted the oxidative NO adsorption. The reactivity of the adsorbed NOx toward H2 was examined for MnOx–CeO2 impregnated with Pd, which is known as a nonselective catalyst toward NO–H2 reaction in the presence of excess oxygen. The Pd/MnOx–CeO2 catalyst after saturated by the NO uptake could be regenerated by micropulse injections of H2 at 150 °C. Evidence was presented to show that the role of Pd is to generate reactive hydrogen atoms, which spillover onto the MnOx–CeO2 surface and reduce nitrite/nitrate adsorbing thereon. Because of the lower reducibility of nitrate and the competitive H2–O2 combustion, H2–NO reaction was suppressed to a certain extent in the presence of O2. Nevertheless, Pd/MnOx–CeO2 attained 65% NO-conversion in a steady stream of 0.08% NO, 2% H2, and 6% O2 in He at as low as 150 °C, compared to ca. 30% conversion for Pd/γ–Al2O3 at the same temperature. The combination of NOx-sorbing materials and H2-activation catalysts is expected to pave the way to development of novel NOx-sorbing catalysts for selective deNOx at very low temperatures.  相似文献   

17.
Ag/Au/Fe3O4/graphene composites prepared by a hydrothermal method demonstrated excellent activation of H2O2 and were used to degrade methylene blue (MB) in solution in the presence of organic acids and inorganic ions under light and ultrasound irradiation. The physicochemical properties of the obtained composites were characterized using various methods. The results showed that the composites exhibited excellent magnetic properties, crystallinity, and stability. The results of catalysis experiments revealed that the removal efficiency of MB increased when Ag and Au were both incorporated into the Fe3O4/graphene/H2O2 system compared with the removal efficiency achieved with separate Ag-Fe3O4/graphene/H2O2 and Au-Fe3O4/graphene/H2O2 systems, indicating a substantial synergistic interaction between the two metallic nanoparticles and the Fe3O4/graphene/H2O2 systems. The presence of an organic acid accelerated degradation of the MB/H2O2 system, whereas almost all of the investigated anions inhibited the degradation of MB; their inhibition effects followed the order CO32? > NO3? > Cl? > F? > H2PO4? > SO42? > I?. Cations of Na+, K+, Ca2+, and Mg2+ also suppressed MB degradation, likely because of the influence of Cl? coexisting in the solutions.  相似文献   

18.
A series of five binary complexes, i.e. three cocrystals and two molecular salts, using 2‐chloro‐4‐nitrobenzoic acid as a coformer have been produced with five commonly available compounds, some of pharmaceutical relevance, namely, 2‐chloro‐4‐nitrobenzoic acid–isonicotinamide (1/1), C7H4ClNO4·C6H6N2O, 2‐chloro‐4‐nitrobenzoic acid–3,3‐diethylpyridine‐2,4(1H,3H)‐dione (2/1), 2C7H4ClNO4·C9H13NO2, 2‐chloro‐4‐nitrobenzoic acid–pyrrolidin‐2‐one (1/1), C7H4ClNO4·C4H7NO, 2‐carboxypiperidinium 2‐chloro‐4‐nitrobenzoate, C6H12NO2?·C7H3ClNO4?, and (2‐hydroxyethyl)ammonium 2‐chloro‐4‐nitrobenzoate, C2H8NO+·C7H3ClNO4?. The coformer falls under the classification of a `generally regarded as safe' compound. All five complexes make use of a number of different heteromeric hydrogen‐bonded interactions. Intermolecular potentials were evaluated using the CSD‐Materials module.  相似文献   

19.
A novel SrSn(OH)6 photocatalyst with large plate and particle size were synthesized via a facile chemical precipitation method.The photocatalytic activity of the SrSn(OH)6 was evaluated by the removal of NO at ppb level under UV light irradiation.Based on the ESR measurements,SrSn(OH)6 photocatalyst was found to have the ability to generate the main active species of O2·-,·OH and 1 O2 during the photocatalyti...  相似文献   

20.
Vibrational chemiluminescence in the Δν1 = Δν3 = ?1 band of NO2 is observed both in the O + NO and O3 + NO reactions and shown to be emitted by molecules with up to 11 000 cm?1 of vibrational energy. Quenching rate constants of NO23 are estimated ranging from about 6 × 10?14 for Ar to about 3 × 10?12 cm3 s?1 for NO2. The ratio of vibrational to electronic emission is 0.06 ± 0.03 for O + NO and 5.3 ± 1.0 for O3 + NO. It is suggested that vibrationally excited NO2 is a major product of that channel of the O3 + NO reaction which forms ground-state NO2(2A1) directly.  相似文献   

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