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1.
The photocatalytic reduction of CO2 is a promising strategy to generate chemical fuels. However, this reaction usually suffers from low photoactivity because of insufficient light absorption and rapid charge recombination. Defect engineering has become an effective approach to improve the photocatalytic activity. Herein, ultra-thin (~ 4.1 nm) carbon-doped Bi2WO6 nanosheets were prepared via hydrothermal treatment followed by calcination. The ultra-thin nanosheet structure of the catalyst not only provides more active sites but also shortens the diffusion distance of charge carriers, thereby suppressing charge recombination. Moreover, carbon doping could successfully extend the light absorption range of the catalyst and remarkably promote charge separation, thus inhibiting recombination. As a result, the as-prepared Bi2WO6 photocatalyst with ultra-thin nanosheet structure and carbon doping exhibits enhanced photocatalytic CO2 reduction performance, which is twice that of pristine ultra-thin Bi2WO6 nanosheet. This study highlights the importance of defect engineering in photocatalytic energy conversion and provides new insights for fabricating efficient photocatalysts. 相似文献
2.
Composite materials of Fe/Al 2O 3, which consist of small particles of iron supported by thermally stable alumina even at 500–700 °C, have been widely used in the water-gas shift reaction for natural gas reforming. Therefore, Fe/Al 2O 3 is one of the promising candidates for re-transformation of exhausted CO 2 into fuels such as alcohols and hydrocarbons. The development of a CO 2 reforming system using the composite materials of Fe/Al 2O 3 through CO 2 reduction to CO, dissociation of water into hydrogen, and methanol synthesis has been investigated. It was found that dry and steam (i.e. wet) reforming of CO 2 produced almost the same amount of CO. At a temperature above 500 °C, maximal and saturated yields of CO and H 2 from CO 2 and water were obtained. However, this CO 2 reforming system requires higher-pressure conditions from several tens to hundreds standard atmospheric pressure in order to achieve high yield and selectivity for methanol production. In this study we developed the modified CO 2 reforming system by the utilization of Ni and/or Cu instead of Fe in order to obtain other types of useful products such as CO, CH 4, and carbon, more efficiently and selectively under atmospheric pressure. When Ni or Cu was used, conversion of CO 2 was reduced to 76%, while 9% of methane was detected in the case of Ni. On the other hand, though the CO 2 conversion reduced half of the Fe, the selectivity of CO from CO 2 increased to 95% in the case of Cu. 相似文献
3.
Cr(VI) and phenol are toxic contaminants that need to be treated, and different methods have been researched to simultaneously remove these two contaminants from industrial wastewater. In this study, Cr(VI) was used as a novel Fenton-like catalyst in phenol degradation by H2O2. In the pH range of 3.0‒11.0, the degradation efficiency of phenol decreased with elevated pH. At pH = 3.0, 100 mg/L phenol was effectively degraded by 2 mmol/L Cr(VI) and 20 mmol/L H2O2. At pH = 7.0 and the same conditions as those of pH = 3.0, 79% of 100 mg/L phenol was removed within 6 h, which was an improvement in pH limitation compared with the Fe(II)-mediated Fenton reaction. Quenching experiments indicated that ·OH generated from the catalysis of H2O2 by Cr(V) instead of Cr(VI) was the primary oxidant that degraded phenol. When pyrophosphate was added in the Cr(VI)/H2O2 system, complexes with the Cr(V) intermediate rapidly formed and inhibited H2O2 decomposition, implying that the decomposition of H2O2 to ·OH was catalyzed by Cr(V) instead of Cr(VI). The presence of anions such as chloride and sulfate had insignificant effect on the degradation of phenol. TOC and UV analyses suggest that phenol could not be completely oxidized to CO2 and H2O, and the intermediates identified by high performance liquid chromatography further indicates that maleic acid and benzoquinone were intermediates which may be further degraded into short chain acids, primarily maleic, formic, acetic, and oxalic acids, and eventually into CO2 and H2O. Considering that more than 50% Cr(VI) can also be removed during this process, the Cr(VI)/H2O2 system is more appropriate for the simultaneous removal of Cr(VI) and phenol contaminants from industrial wastewater. 相似文献
4.
A semi-analytical Monte Carlo (SMC) simulation was developed to simulate the propagation of laser-induced fluo- rescence (LIF) in an optically participating spray, which simultaneously exhibits spectrally dependent emission, anisotropic scattering, absorption, and re-emission. The SMC simulation is described and then applied to an experimental configuration of a cloud of polydisperse droplets composed of water and sulforhodamine B dye. In the SMC simulation, the collected LIF flux on the remote receptor element is calculated as the global contribution from the emissive source, single, twice, … and nth collision events in any sequence. The effects on the fluorescence photons propagation of spray parameters like the dye concentration, droplets concentration, and droplets size are examined. Three spectral bands representing different optical properties are chosen to analyze the interference of absorption, scattering and re-emission on the detected LIF flux. The obtained spectral LIF flux distribution on the receptor demonstrates a “red shift” phenomenon. 相似文献
5.
The metal oxide/nitrogen-doped carbon (NC) compounds zirconium oxide/NC (ZrO2/NC) and cerium oxide/NC (CeO2/NC) were synthesized via the pyrolysis of polyaniline on the metal oxide surface. The characterization of the ZrO2/NC and CeO2/NC catalysts showed more active CO2 reduction reaction activity than that of NC catalyst without metal oxide. Gas chromatography analysis revealed that CO and H2 were the primary products, and no liquid-phase products were detected via proton nuclear magnetic resonance spectroscopy or high-performance liquid chromatography. The maximum Faraday efficiency of ZrO2/NC reached 90% at − 0.73 V (vs. RHE), with the current density of CO at 5.5 mA/cm2; this Faraday efficiency value was higher than that of NC (41%), with the current density of CO at 3.1 mA/cm2. The interaction between the metal oxide and carbon allowed the efficient formation of defect sites, especially imine-type nitrogen, strengthening the adsorption of the key reaction intermediate CO2•− and thus promoting the CO2 reduction reaction. 相似文献
6.
Capturing CO2 from the atmosphere and converting it into fuels are an efficient strategy to stop the deteriorating greenhouse effect and alleviate the energy crisis. Among various CO2 conversion approaches, electrocatalytic CO2 reduction reaction (CO2RR) has received extensive attention because of its mild operating conditions. However, the high onset potential, low selectivity toward multi-carbon products and poor cruising ability of CO2RR impede its development. To regulate product distribution, previous studies performed electrocatalyst modification using several universal methods, including composition manipulation, morphology control, surface modification, and defect engineering. Recent studies have revealed that the cathode and electrolytes influence the selectivity of CO2RR via pH changes and ionic effects, or by directly participating in the reduction pathway as cocatalysts. This review summarizes the state-of-the-art optimization strategies to efficiently enhance CO2RR selectivity from two main aspects, namely the cathode electrocatalyst and the electrolyte. 相似文献
7.
Well-cubic perovskite lanthanum aluminate (LaAlO 3) film on (110) silicon substrate was fabricated by sol-gel method with corresponding inorganic salts. Lanthanum acetate and
aluminum acetate glacial acetic acid solutions were prepared via ligand exchange starting from lanthanum nitrate hexahydrate
and aluminum nitrate hexahydrate after being refluxed. (CH 3CO) 2O removed nitrates and the crystallized H 2O completely, acetylacetone (AcAc) was partially bidentated with metallic ion of the metallic acetates and formed La(OAc) 3−x
(AcAc)
x
which were hydrolyzed into La(AcAc) 3−x(OH)
x
by adding 10 ml 0.4% methyl cellulose (MCL) solution. The La(AcAc) 3−x
(OH)
x
, polymerizing and combining with MCL, formed the LaAlO 3 sol precursor with heteropolymeric structure and formed film easily. The epitaxial LaAlO 3 film on Si(110) substrate was crystallized after being annealed in thermal annealing furnace for 650–750 °C/30 min. The morphologies
and microstructures were characterized. The refractive index of the LAO film was 1.942 to 2.007; the dielectric constant and
the dissipation factors were estimated to be 23–26 and 2.1×10 −4−2.4×10 −4 respectively.
Project (No. 2002CB613305) supported by the National Basic Research Program (973) of China 相似文献
8.
研究目的：研究方法：重要结论：确定氢氧化钠溶液化学吸收硫酰氟的传质反应动力学区域,建立增强因子模型。研究气液传质测定设备双搅拌釜中氢氧化钠溶液化学吸收硫酰氟的过程,并结合实验研究与理论分析建立了增强因子模型。基于氢氧化钠溶液化学吸收硫酰氟过程的实验研究,确定了氢氧化钠溶液化学吸收硫酰氟的传质反应动力学区域为快速拟一级反应。得到了298K下其二级反应速率常数为1．44m3／（mol·s）,并建立了增强因子模型E=68．08CBL1/2,为脱除熏蒸后残留硫酰氟的工业化应用提供了理论依据。 相似文献
9.
Chemical absorption of CO2 into aqueous slurries of Ca(OH)2 was studied in a stirred thermostatic reactor. The influence of solid loading and stirring speed on absorption rate were investigated experimentally, and the results show that the enhancement factor increases with particle content due to the increase of reactive particles in the gas-liquid interfacial region. The absorption process was controlled by the diffusion of gas molecules in slurry. The influence of stirring intensity on enhancement factor is an integration of gas-liquid and liquid-solid mass transfer variation. A novel prediction model of enhancement factors was proposed with the partition of interface into two various zones, and the prediction values by the presented model are in agreement with the experimental data. 相似文献
10.
Conversion of carbon dioxide (CO2) into valuable chemicals and renewable fuels via photocatalysis represents an eco-friendly route to achieve the goal of carbon neutralization. Although various types of semiconductor materials have been intensively explored, some severe issues, such as rapid charge recombination and sluggish redox reaction kinetics, remain. In this regard, cocatalyst modification by trapping charges and boosting surface reactions is one of the most efficient strategies to improve the efficiency of semiconductor photocatalysts. This review focuses on recent advances in CO2 photoreduction over cost-effective and earth-abundant cobalt (Co)-based cocatalysts, which are competitive candidates of noble metals for practical applications. First, the functions of Co-based cocatalysts for promoting photocatalytic CO2 reduction are briefly discussed. Then, different kinds of Co-based cocatalysts, including cobalt oxides and hydroxides, cobalt nitrides and phosphides, cobalt sulfides and selenides, Co single-atom, and Co-based metal–organic frameworks (MOFs), are summarized. The underlying mechanisms of these Co-based cocatalysts for facilitating CO2 adsorption–activation, boosting charge separation, and modulating intermediate formation are discussed in detail based on experimental characterizations and density functional theory calculations. In addition, the suppression of the competing hydrogen evolution reaction using Co-based cocatalysts to promote the product selectivity of CO2 reduction is highlighted in some selected examples. Finally, the challenges and future perspectives on constructing more efficient Co-based cocatalysts for practical applications are proposed. 相似文献
11.
The phase equilibrium data of CO_2 –hydrocarbon binary mixtures are important for the design and operation of CO_2 flooding, coal liquefaction, and supercritical extraction processes. Numerous pieces of binary phase equilibrium data have been obtained. Thus, models for the accurate calculation of binary and multicomponent mixtures must be developed on the basis of existing data. In this work, 3578 vapor–liquid phase equilibrium data points for 10 CO_2 –hydrocarbon binary mixtures, including CO_2 –butane, CO_2 –pentane, CO_2 –isopentane, CO_2 –hexane, CO_2 –benzene, CO_2 –heptane, CO_2 –octane, CO_2 –nonane, CO_2 –decane, and CO_2 –undecane, were collected. The PR and PR-BM equations of state(EOS) in combination with relevant mixing rules were used to calculate the phase equilibrium data of the CO_2 –hydrocarbon binary mixtures. The binary interaction parameter k ij in the PR EOS was temperature independent, whereas parameters in the PR-BM EOS were functions of temperature. Thus, the phase equilibrium data and other thermodynamic properties of the binary and multicomponent mixtures at different temperatures and pressures can be calculated by using the parameters obtained in this work. The PR-BM EOS performed better than the PR EOS, and the average absolute deviations over the temperature range of 255.98–408.15 K calculated by the PR EOS and PR-BM EOS were less than 5.74% and 3.36%, respectively. The results calculated by the two EOS were compared with those calculated by other models, such as PPR78, PR + LCVM + UNIFAC, KIE + PR EOS + HV, and PSRK. The phase equilibrium data of CO_2 –butane–decane, CO_2 –hexane–decane, and CO_2 –octane–decane ternary mixtures were calculated by the two EOS. The average overall deviations for the CO_2 mole fractions calculated by the two EOS were less than 7.66%. 相似文献
12.
In three experiments, we compared the effectiveness of rainbow writing and retrieval practice, two common methods of spelling instruction. In experiment 1 ( n?=?14), second graders completed 2 days of spelling practice, followed by spelling tests 1 day and 5 weeks later. A repeated measures analysis of variance demonstrated that spelling accuracy for words trained with retrieval practice was higher than for words trained with rainbow writing on both tests ( η p 2 ?=?.49). In experiments 2 (second graders, n?=?16) and 3 (first graders, n?=?12), students completed 2 days of spelling practice followed by a spelling test 1 day later. Results replicated experiment 1; spelling accuracy was higher for words trained with retrieval practice compared with rainbow writing ( η p 2 ?=?.42 and .64, respectively). Furthermore, students endorsed both liking and learning from retrieval practice at least as much as (and sometimes more than) rainbow writing. Results demonstrate that retrieval practice is a more useful (and as engaging) training method than is rainbow writing and extend the well-established testing effect to beginning spellers. 相似文献
13.
This study was conducted to investigate the combined effects of elevated CO 2 levels and cadmium (Cd) on the root morphological traits and Cd accumulation in Lolium multiflorum Lam. and Lolium perenne L. exposed to two CO 2 levels (360 and 1 000 μl/L) and three Cd levels (0, 4, and 16 mg/L) under hydroponic conditions. The results show that elevated
levels of CO 2 increased shoot biomass more, compared to root biomass, but decreased Cd concentrations in all plant tissues. Cd exposure
caused toxicity to both Lolium species, as shown by the restrictions of the root morphological parameters including root length, surface area, volume, and
tip numbers. These parameters were significantly higher under elevated levels of CO 2 than under ambient CO 2, especially for the number of fine roots. The increases in magnitudes of those parameters triggered by elevated levels of
CO 2 under Cd stress were more than those under non-Cd stress, suggesting an ameliorated Cd stress under elevated levels of CO 2. The total Cd uptake per pot, calculated on the basis of biomass, was significantly greater under elevated levels of CO 2 than under ambient CO 2. Ameliorated Cd toxicity, decreased Cd concentration, and altered root morphological traits in both Lolium species under elevated levels of CO 2 may have implications in food safety and phytoremediation. 相似文献
14.
Ultrafine γ-Al 2O 3 particles are synthesized in Triton X-100/ n-hexanol/cyclohexane/water water in oil(w/o) microemulsion by mixing two separately prepared microemulsions containing Al(NO) 3 and (NH 4) 2CO 3 respectively. The ultrafine Al 2O 3 particles are characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD) and their size and distribution
are measured. The effects of water, surfactant and reactant concentrations on the particle size and distribution are studied.
The results show that the particle size and distribution can be changed by varying the preparation conditions, and the size
of the microemulsion droplets has a controlling effect on the size of the particles. A possible mechanism of ultrafine particles
(UFPs) prepared by microemulsions is proposed. 相似文献
15.
In order to clarify the equilibrium components in the hydrolysis solution of boron trifluoride(BF_3-H_2O),the BF_3-H_2O was prepared by mixing BF_3-CH_3OH with large amount of water,in which the stoichiometric concentration of BF_3 is less than 0.1 mol/L.Two ionic equilibrium models were proposed to simulate the hydrolysis equilibrium of BF_3 and tested by special acid-base titration technique.The most accurate ion equilibrium constants were determined.The model,which was assumed to have no HF,was proved to be more representative for the real system and used to simulate the hydrolysis equilibrium of BF_3.The simulation suggested that H~+,BF_4~-,BF_3OH~- and H_3BO_3 were the main species in the dilute hydrolysis solution,while BF_2(OH)_2~- and F~- were insignificant species whose concentrations were both in the order of 10~(-4) mol/L magnitude,and BF(OH)_3~- could be omitted because its concentration almost equaled zero.Meanwhile,the equilibrium constant of the overall ionic reaction at 25℃ was obtained as 161.6. 相似文献
17.
We first report discovery of the spinel-garnet-orthopyroxene granulite with pure CO 2 fluid inclusions from the Fuyun region of the late Paleozoic Altay orogenic belt in Central Asia, NW China. The rock is characterized
by an assemblage of garnet, orthopyroxene spinel, cordierite, biotite, plagioclase and quartz. Symplectites of orthopyroxene
and spinel, and orthopyroxene and cordierite indicate decompression under UHT conditions. Mineral chemistry shows that the
orthopyroxenes have high X Mg and Al 2O 3 contents (up to 9.23 wt%). Biotites are enriched in TiO 2 and X Mg and are stable under granulite facies conditions. The garnet and quartz from the rock carry monophase fluid inclusions which
show peak melting temperatures of around-56.7°C, indicating a pure CO 2 species being presented during the ultrahigh-T metamorphism in the Altay orogenic belt. The inclusions homogenize into a
liquid phase at temperatures around 15.3–23.8°C translating into CO 2 of the order of 0.86–0.88 g/cm 3. Based on preliminary minerals paragenesis, reaction textures and petrogenetic grid considerations, we infer that the rock
was subjected to UHT conditions. The CO 2-rich fluids were trapped during exhumation along a clockwise P-T path following isothermal decompression under UHT conditions.
Project supported by the National Basic Research Program (973) of China (No. 2001CB409801), the Exemplary Young Teacher Education
and Scientific Research Award Plan of China University, and Postdoctoral Fund of China (No. 2003033033), Postdoctoral Fund
of Zhejiang Province, and Starting Fund of Education Ministry, China 相似文献
18.
A new concept of low-cost direct air capture technology integrated with a fertilization system is proposed, as an alternative to the application of air derived CO 2. A moisture swing sorbent can elevate the CO 2 concentration from 400 parts per million (ppm) to several thousand ppm, and this can be used to cultivate plants. Desorption isotherms were determined and are described well by a Langmuir model. The adsorption rate constant and the desorption rate constant were gained at 25 °C, 35 °C, and 45 °C under 1000 ppm concentration of CO 2. In accelerated cultivation experiments, the effects of CO 2 concentration, light intensity, and spectrum on the CO 2 uptake rate of the plants were investigated. A multi-bed desorption system which is capable of providing a continuous and stable CO 2 supply for a greenhouse is demonstrated based on the desorption characteristic and CO 2 uptake feature of plants. An energy and cost assessment for the integrated system was performed and the results indicated that minimum energy requirements and cost estimate of CO 2 are 35.67 kJ/mol and 34.68 USD/t, respectively. This makes direct air capture a competitive and sustainable carbon source for agriculture. 相似文献
19.
Forest plays very important roles in global system with about 35% land area producing about 70% of total land net production. It is important to consider both elevated CO2 concentrations and different soil moisture when the possible effects of elevated CO2 concentration on trees are assessed. In this study, we grew Cinnamomum camphora seedlings under two CO2 concentrations （350 μmol/mol and 500μmnol/mol） and three soil moisture levels [80%, 60% and 40% FWC （field water capacity）] to focus on the effects of exposure of trees to elevated CO2 on underground and aboveground plant growth, and its dependence on soil moisture. The results indicated that high CO2 concentration has no significant effects on shoot height but significantly impacts shoot weight and ratio of shoot weight to height under three soil moisture levels. The response of root growth to CO2 enrichment is just reversed, there are obvious effects on root length growth, but no effects on root weight growth and ratio of root weight to length. The CO2 enrichment decreased 20.42%, 32.78%, 20.59% of weight ratio of root to shoot under 40%, 60% and 80% FWC soil water conditions, respectively. And elevated CO2 concentration significantly increased the water content in aboveground and underground parts. Then we concluded that high CO2 concentration favours more tree aboveground biomass growth than underground biomass growth under favorable soil water conditions. And CO2 enrichment enhanced lateral growth of shoot and vertical growth of root. The responses of plants to elevated CO2 depend on soil water availability, and plants may benefit more from CO2 enrichment with sufficient water supply. 相似文献
20.
对自我实现的探求是贯穿于劳伦斯小说《虹》中的主题性线索。小说以“虹”为意象,通过布兰文家族三代人之间各自美好婚姻追求的幻灭,探求了在资本主义工业文明社会中自我实现的不可能性。试图从存在主义文学理论对《虹》加以解读,并指出布兰文家族自我实现的幻灭实际上是作者向世人敲响的一记警钟：在人性日益异化的工业文明浪潮中,对于幽住在极端个人主义和自由主义死胡同里的现代人类来说,自我实现只是一种纯粹的幻想,一条美丽无比、飘缈虚幻的“彩虹”而已。 相似文献
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