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1.
Photocatalytic reduction of CO\begin{document}$_2$\end{document} into various types of fuels has attracted great interest, and serves as a potential solution to addressing current global warming and energy challenges. In this work, Ag-Cu nanoparticles are densely supported on N-doped TiO\begin{document}$_2$\end{document} nanowire through a straightforward nanofabrication approach. The range of light absorption by N-doped TiO\begin{document}$_2$\end{document} can be tuned to match the plasmonic band of Ag nanoparticles, which allows synergizing a resonant energy transfer process with the Schottky junction. Meanwhile, Cu nanoparticles can provide active sites for the reduction of CO\begin{document}$_2$\end{document} molecules. Remarkably, the performance of photocatalytic CO\begin{document}$_2$\end{document} reduction is improved to produce CH\begin{document}$_4$\end{document} at a rate of 720 \begin{document}$\mu$\end{document}mol\begin{document}$\cdot$\end{document}g\begin{document}$^{-1}$\end{document}\begin{document}$\cdot$\end{document}h\begin{document}$^{-1}$\end{document} under full-spectrum irradiation.  相似文献   

2.
The development of \begin{document}$\rm{Bi}_2$\end{document}W\begin{document}$\rm{O}_6$\end{document}-based materials has become one of research hotspots due to the increasing demands on high-efficient photocatalyst responding to visible light. In this work, the effect of high energy radiation (\begin{document}$\gamma$\end{document}-ray) on the structure and the photocatalytic activity of \begin{document}$\rm{Bi}_2$\end{document}W\begin{document}$\rm{O}_6$\end{document} nanocrystals was first studied. No morphological change of \begin{document}$\rm{Bi}_2$\end{document}W\begin{document}$\rm{O}_6$\end{document} nanocrystals was observed by SEM under \begin{document}$\gamma$\end{document}-ray radiation. However, the XRD spectra of the irradiated \begin{document}$\rm{Bi}_2$\end{document}W\begin{document}$\rm{O}_6$\end{document} nanocrystals showed the characteristic 2\begin{document}$\theta$\end{document} of (113) plane shifts slightly from 28.37\begin{document}$^{\rm{o}}$\end{document} to 28.45\begin{document}$^{\rm{o}}$\end{document} with the increase of the absorbed dose, confirming the change in the crystal structure of \begin{document}$\rm{Bi}_2$\end{document}W\begin{document}$\rm{O}_6$\end{document}. The XPS results proved the crystal structure change was originated from the generation of oxygen vacancy defects under high-dose radiation. The photocatalytic activity of \begin{document}$\rm{Bi}_2$\end{document}W\begin{document}$\rm{O}_6$\end{document} on the decomposition of methylene blue (MB) in water under visible light increases gradually with the increase of absorbed dose. Moreover, the improved photocatalytic performance of the irradiated \begin{document}$\rm{Bi}_2$\end{document}W\begin{document}$\rm{O}_6$\end{document} nanocrystals remained after three cycles of photocatalysis, indicating a good stability of the created oxygen vacancy defects. This work gives a new simple way to improve photocatalytic performance of \begin{document}$\rm{Bi}_2$\end{document}W\begin{document}$\rm{O}_6$\end{document} through creating oxygen vacancy defects in the crystal structure by \begin{document}$\gamma$\end{document}-ray radiation.  相似文献   

3.
Distinguished from commonly used Fe\begin{document}$_2$\end{document}O\begin{document}$_3$\end{document} and Fe\begin{document}$_3$\end{document}O\begin{document}$_4$\end{document}, a three-dimensional multilevel macro-micro-mesoporous structure of FeC\begin{document}$_2$\end{document}O\begin{document}$_4$\end{document}/graphene composite has been prepared as binder-free electrode for supercapacitors. The as-prepared materials are composed of macroporous graphene and microporous/mesoporous ferrous oxalate. Generally, the decomposition voltage of water is 1.23 V and the practical voltage window limit is about 2 V for asymmetric supercapacitors in aqueous electrolytes. When FeC\begin{document}$_2$\end{document}O\begin{document}$_4$\end{document}/rGO hydrogel was used as the negative electrode and a pure rGO hydrogel was used as the positive electrode, the asymmetrical supercapacitor voltage window raised to 1.7 V in KOH (1.0 mol/L) electrolyte and reached up to 2.5 V in a neutral aqueous Na\begin{document}$_2$\end{document}SO\begin{document}$_4$\end{document} (1.0 mol/L) electrolyte. Correspondingly it also exhibits a high performance with an energy density of 59.7 Wh/kg. By means of combining a metal oxide that owns micro-mesoporous structure with graphene, this work provides a new opportunity for preparing high-voltage aqueous asymmetric supercapacitors without addition of conductive agent and binder.  相似文献   

4.
OX\begin{document}$_2$\end{document} (X=halogen) molecules was studied theoretically. Calculation results show that delocalized \begin{document}$\pi_3^6$\end{document} bonds exist in their electronic structures and O atoms adopt the sp\begin{document}$^2$\end{document} type of hybridization, which violates the prediction of the valence shell electron pair repulsion theory of sp\begin{document}$^3$\end{document} type. Delocalization stabilization energy is proposed to measure the contribution of delocalized \begin{document}$\pi_3^6$\end{document} bond to energy decrease and proves to bring extra-stability to the molecule. These phenomena can be summarized as a kind of coordinating effect.  相似文献   

5.
Hydrogen evolution reaction (HER) is the major cathodic reaction which competes \begin{document}${\rm C}\rm{O}_\rm{2}$\end{document} reduction reaction (\begin{document}${\rm C}\rm{O}_\rm{2}$\end{document} RR) on Pt electrode. Molecular level understanding on how these two reactions interact with each other and what the key factors are of \begin{document}${\rm C}\rm{O}_\rm{2}$\end{document} RR kinetics and selectivity will be of great help in optimizing electrolysers for \begin{document}${\rm C}\rm{O}_\rm{2}$\end{document} reduction. In this work, we report our results of hydrogen evolution and \begin{document}${\rm C}\rm{O}_\rm{2}$\end{document} reduction on Pt(111) and Pt film electrodes in \begin{document}${\rm C}\rm{O}_\rm{2}$\end{document} saturated acid solution by cyclic voltammetry and infrared spectroscopy. In solution with pH > 2, the major process is HER and the interfacial pH increases abruptly during HER; \begin{document}${\rm C}\rm{O}_\rm{ad}$\end{document} is the only adsorbed intermediate detected in \begin{document}${\rm C}\rm{O}_\rm{2}$\end{document} reduction by infrared spectroscopy; the rate for \begin{document}${\rm C}\rm{O}_\rm{ad}$\end{document} formation increases with the coverage of UPD-H and reaches maximum at the onset potential for HER; the decrease of \begin{document}${\rm C}\rm{O}_\rm{ad}$\end{document} formation under HER is attributed to the available limited sites and the limited residence time for the reduction intermediate (\begin{document}$\rm{H}_\rm{ad}$\end{document}), which is necessary for \begin{document}${\rm C}\rm{O}_\rm{2}$\end{document} adsorption and reduction.  相似文献   

6.
Graphene oxide (GO) is a kind of water soluble two-dimensional materials containing a large amount of oxygen-containing groups which infuse GO with water solubility, biocompatibility and functionality, etc. But GO can be easily reduced by losing oxygen-containing groups under some circumstances such as irradiation of \begin{document}$\gamma$\end{document}-ray or ultraviolet (UV). In this work, we found that acetone can significantly slow down the reduction process of GO under the irradiation of either \begin{document}$\gamma$\end{document}-ray or UV, which was supported by analysis results with UV-visible (UV-Vis) absorption spectra, X-ray photoelectron spectroscopy, etc. Acetone can capture and remove strongly reducible hydrated electrons generated under \begin{document}$\gamma$\end{document}-irradiation. GO reduction by UV also involves electron transfer process which can be affected by the presence of acetone. Hence, acetone can be used to stabilize, adjust the radiation reduction process of GO. This would be interesting not only in radiation and radiation protection, but also in understanding the redox properties of GO.  相似文献   

7.
This work developed a one-step process for renewable p-xylene production by co-catalytic fast pyrolysis (co-CFP) of cellulose and methanol over the different metal oxides modified ZSM5 catalysts. It has been proven that \begin{document}${\rm{L}}{{\rm{a}}_{\rm{2}}}{{\rm{O}}_{\rm{3}}}$\end{document}-modified ZSM5(80) catalyst was an effective one for the production of bio-based p-xylene. The selectivity and yield of p-xylene strongly depended on the acidity of the catalysts, reaction temperature, and methanol content. The highest p-xylene yield of 14.5 C-mol% with a p-xylene/xylenes ratio of 86.8% was obtained by the co-CFP of cellulose with 33wt% methanol over 20%\begin{document}${\rm{L}}{{\rm{a}}_{\rm{2}}}{{\rm{O}}_{\rm{3}}}$\end{document}-ZSM5(80) catalyst. The deactivation of the catalysts during the catalytic pyrolysis process was investigated in detail. The reaction pathway for the formation of p-xylene from cellulose was proposed based on the analysis of products and the characterization of catalysts.  相似文献   

8.
Although there are diverse bond features of Ti and O atoms, so far only several isomers have been reported for each (TiO\begin{document}$_2$\end{document})\begin{document}$_n$\end{document} cluster. Instead of the widely used global optimization, in this work, we search for the low-lying isomers of (TiO\begin{document}$_2$\end{document})\begin{document}$_n$\end{document} (\begin{document}$n$\end{document}=2\begin{document}$-$\end{document}8) clusters with up to 10000 random sampling initial structures. These structures were optimized by the PM6 method, followed by density functional theory calculations. With this strategy, we have located many more low-lying isomers than those reported previously. The number of isomers increases dramatically with the size of the cluster, and about 50 isomers were found for (TiO\begin{document}$_2$\end{document})\begin{document}$_7$\end{document} and (TiO\begin{document}$_2$\end{document})\begin{document}$_8$\end{document} with the energy within kcal/mol. Furthermore, new lowest isomers have been located for (TiO\begin{document}$_2$\end{document})\begin{document}$_5$\end{document} and (TiO\begin{document}$_2$\end{document})\begin{document}$_8$\end{document}, and isomers with three terminal oxygen atoms, five coordinated oxygen atoms as well as six coordinated titanium atoms have been located. Our work highlights the diverse structural features and a large number of isomers of small TiO\begin{document}$_2$\end{document} clusters.  相似文献   

9.
A rod-like NiCo\begin{document}$_2$\end{document}O\begin{document}$_4$\end{document} modified glassy carbon electrode was fabricated and used for non-enzymatic glucose sensing. The NiCo\begin{document}$_2$\end{document}O\begin{document}$_4$\end{document} was prepared by a facile hydrothermal reaction and subsequently treated in a commercial microwave oven to eliminate the residual water introduced during the hydrothermal procedure. Structural analysis showed that there was no significant structural alteration before and after microwave treatment. The elimination of water residuals was confirmed by the stoichiometric ratio change by using element analysis. The microwave treated NiCo\begin{document}$_2$\end{document}O\begin{document}$_4$\end{document} (M-NiCo\begin{document}$_2$\end{document}O\begin{document}$_4$\end{document}) showed excellent performance as a glucose sensor (sensitivity 431.29 \begin{document}$\mu $\end{document}A\begin{document}$\cdot$\end{document}mmol/L\begin{document}$^{-1}$\end{document}\begin{document}$\cdot$\end{document}cm\begin{document}$^{-2}$\end{document}). The sensing performance decreases dramatically by soaking the M-NiCo\begin{document}$_2$\end{document}O\begin{document}$_4$\end{document} in water. This result indicates that the introduction of residual water during hydrothermal process strongly affects the electrochemical performance and microwave pre-treatment is crucial for better sensory performance.  相似文献   

10.
The electrocatalytic carbon dioxide reduction reaction (CO2RR) producing HCOOH and CO is one of the most promising approaches for storing renewable electricity as chemical energy in fuels. SnO2 is a good catalyst for CO2-to-HCOOH or CO2-to-CO conversion, with different crystal planes participating the catalytic process. Among them, (110) surface SnO2 is very stable and easy to synthesisze. By changing the ratio of Sn: O for SnO2(110), we have two typical SnO2 thin films: fully oxidized (stoichiometric) and partially reduced. In this work, we are concerned with different metals (Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Os, Ir, Pt, and Au)-doped SnO2(110) with different activity and selectivity for CO2RR. All these changes are manipulated by adjusting the ratio of Sn: O in (110) surface. The results show that stochiometric and reduced Cu/Ag doped SnO2(110) have different selectivity for CO2RR. More specifically, stochiometric Cu/Ag-doped SnO2(110) tends to generate CO(g). Meanwhile, the reduced surface tends to generate HCOOH(g). Moreover, we also considered the competitive hydrogen evolution reaction (HER). The catalysts SnO2(110) doped by Ru, Rh, Pd, Os, Ir, and Pt have high activity for HER, and others are good catalysts for CO2RR.  相似文献   

11.
在ADC(2)水平上通过轨线面跳跃方法模拟了硝酸甲酯的非绝热动力学.结果证实该体系存在快速的非绝热动力学过程,导致了体系回到电子基态.当动力学从S1和S2电子态开始时,光解产物是CH3O+NO2,这个发现与实验研究的结果以及更高精度的XMS-CASPT2水平上模拟出的结果一致.在ADC(2)水平上,当动力学从S3态开始时,光解产物依然是CH3O+NO2.该研究表明:ADC(2)方法可用于研究硝酸甲酯在长波下的光解机理,然而无法用于理解其在短波段下的光解动力学.本文为在ADC(2)水平上处理类似化合物的光诱导过程提供了有价值的信息.  相似文献   

12.
Reduced graphene oxide is the precursor to produce graphene in a large scale; however, to date, there has been no consensus on the electronic structure of reduced graphene oxide. In this study, we carried out an \begin{document}$ ab $\end{document} \begin{document}$ initio $\end{document} molecular dynamics simulation to investigate the adsorption process of hydroxyl groups on graphene surface. During the adsorption process, the OH group needs to firstly pass through a physical adsorption complex with the OH above the bridge site of two carbon atoms, next to surmount a transition state, then to be adsorbed at the atop site of a carbon atom. With a 5\begin{document}$ \times $\end{document}5 graphene surface, up to 6 hydroxyl groups can be adsorbed on the graphene surface, indicating the concentration coverage of the hydroxyl groups on graphene surface is about 12%. The simulation results show that the negative adsorption energy increases linearly as the number of adsorbed hydroxyl groups increases, and the band gap also increases linearly with the number of adsorbed hydroxyl groups.  相似文献   

13.
We report full-dimensional and fully coupled quantum bound-state calculations of the \begin{document}$ J $\end{document} = 1 intra- and intermolecular rovibrational states of two isotopologues of the hydrogen chloride-water dimer, HCl-H\begin{document}$ _2 $\end{document}O (HH) and DCl-H\begin{document}$ _2 $\end{document}O (DH). The present study complements our recent theoretical investigations of the \begin{document}$ J $\end{document} = 0 nine-dimensional (9D) vibrational level structure of these and two other H/D isotopologues of this noncovalently bound molecular complex, and employs the same accurate 9D permutation invariant polynomial-neural network potential energy surface. The calculations yield all intramolecular vibrational fundamentals of the HH and DH dimers and the low-energy intermolecular rovibrational states in these intramolecular vibrational manifolds. The results are compared with those of the 9D \begin{document}$ J $\end{document} = 0 calculations of the same dimers. The energy differences between the \begin{document}$ K $\end{document} = 1 and \begin{document}$ K $\end{document} = 0 eigenstates exhibit pronounced variations with the intermolecular rovibrational states, for which a qualitative explanation is provided.  相似文献   

14.
We performed extensive quasiclassical trajectory calculations for the H+C\begin{document}$_2$\end{document}D\begin{document}$_2$\end{document}\begin{document}$\rightarrow$\end{document}HD+C\begin{document}$_2$\end{document}D/D\begin{document}$_2$\end{document}+C\begin{document}$_2$\end{document}H reaction based on a recently developed, global and accurate potential energy surface by the fundamental-invariant neural network method. The direct abstraction pathway plays a minor role in the overall reactivity, which can be negligible as compared with the roaming pathways. The acetylene-facilitated roaming pathway dominates the reactivity, with very small contributions from the vinylidene-facilitated roaming. Although the roaming pathways proceed via the short-lived or long-lived complex forming process, the computed branching ratio of product HD to D\begin{document}$_2$\end{document} is not far away from 2:1, implying roaming dynamics for this reaction is mainly contributed from the long-lived complex-forming process. The resulting angular distributions for the two product channels are also quite different. These computational results give valuable insights into the significance and isotope effects of roaming dynamics in the biomolecular reactions.  相似文献   

15.
Manipulating the chemical reactivity of graphene toward oxygen reduced reduction (ORR) is of particular interest for both fundamental research and practical application in fuel cell. Deposing graphene on selected substrate provides a structure-intact strategy to enhance its chemical reactivity due to substrate-induced charge and interface effect. Here, we report the graphene deposited on one-dimensional electride Y\begin{document}$_5$\end{document}Si\begin{document}$_3$\end{document} as an effective ORR catalyst in acidic media. Thermodynamic calculations suggest that depositing graphene on electride materials can facilitate the protonation of O\begin{document}$_2$\end{document}, which is the rate-determining step based on the four-electron reaction pathway and thus promote the ORR activity. Further electronic calculations reveal that low work function (3.5 eV), superior electrical conductivity and slight charge transfer from substrate to graphene result in the enhanced ORR performance of graphene. These findings shed light on the rational design of ORR catalysts based on graphitic materials and emphasize the critical role of substrates for energy-related electrochemical reactions.  相似文献   

16.
Hybrid density functional theory calculations on the structures, vibrational frequencies, electron binding and dissociation energies, and bonding properties of CuO$_{3}^{-}$ and CuO3 species have been carried out. Stable isomers containing an O3 subunit and composed of O2 bound to CuO have been located on the potential energy hypersurfaces of CuO$_{3}^{-}$ and CuO3. The isomers formed by O2 bonded to CuO in side‐on and end‐on coordination are more stable than those containing an O3 subunit. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 81: 162–168, 2001  相似文献   

17.
The divergent behavior of C-H bond oxidations of aliphatic substrates compared to those of aromatic substrates shown in Gupta's experiment was mechanistically studied herein by means of density functional theory calculations. Our calculations reveal that such difference is caused by different reaction mechanisms between two kinds of substrates (the aliphatic cyclohexane, 2, 3-dimethylbutane and the aromatic toluene, ethylbenzene and cumene). For the aliphatic substrates, C-H oxidation by the oxidant Fe\begin{document}$^{\rm{V}}$\end{document}(O)(TAML) is a hydrogen atom transfer process; whereas for the aromatic substrates, C-H oxidation is a proton-coupled electron transfer (PCET) process with a proton transfer character on the transition state, that is, a proton-coupled electron transfer process holding a proton transfer-like transition state (PCET(PT)). This difference is caused by the strong \begin{document}$\pi$\end{document}-\begin{document}$\pi$\end{document} interactions between the tetra-anionic TAML ring and the phenyl ring of the aromatic substrates, which has a "pull" effect to make the electron transfer from substrates to the Fe=O moiety inefficient.  相似文献   

18.
In this work, we investigated the methanol steam reforming (MSR) reaction (CH\begin{document}$_3$\end{document}OH+H\begin{document}$_2$\end{document}O \begin{document}$\rightarrow$\end{document}CO\begin{document}$_2$\end{document}+3H\begin{document}$_2$\end{document}) catalyzed by \begin{document}$\alpha$\end{document}-MoC by means of density functional theory calculations. The adsorption behavior of the relevant intermediates and the kinetics of the elementary steps in the MSR reaction are systematically investigated. The results show that, on the \begin{document}$\alpha$\end{document}-MoC(100) surface, the O\begin{document}$-$\end{document}H bond cleavage of CH\begin{document}$_3$\end{document}OH leads to CH\begin{document}$_3$\end{document}O, which subsequently dehydrogenates to CH\begin{document}$_2$\end{document}O. Then, the formation of CH\begin{document}$_2$\end{document}OOH between CH\begin{document}$_2$\end{document}O and OH is favored over the decomposition to CHO and H. The sequential dehydrogenation of CH\begin{document}$_2$\end{document}OOH results in a high selectivity for CO\begin{document}$_2$\end{document}. In contrast, the over-strong adsorption of the CH\begin{document}$_2$\end{document}O intermediate on the \begin{document}$\alpha$\end{document}-MoC(111) surface leads to its dehydrogenation to CO product. In addition, we found that OH species, which is produced from the facile water activation, help the O\begin{document}$-$\end{document}H bond breaking of intermediates by lowering the reaction energy barrier. This work not only reveals the catalytic role played by \begin{document}$\alpha$\end{document}-MoC(100) in the MSR reaction, but also provides theoretical guidance for the design of \begin{document}$\alpha$\end{document}-MoC-based catalysts.  相似文献   

19.
The NH(\begin{document}$a^1$\end{document}\begin{document}$\Delta$\end{document})+CO(\begin{document}$X^1$\end{document}\begin{document}$\Sigma^+$\end{document}) product channel for the photodissociation of isocyanic acid (HNCO) on the first excited singlet state S\begin{document}$_1$\end{document} has been investigated by means of time-sliced ion velocity map imaging technique at photolysis wavelengths around 201 nm. The CO product was detected through (2+1) resonance enhanced multiphoton ionization (REMPI). Images were obtained for CO products formed in the ground and vibrational excited state (\begin{document}$v$\end{document}=0 and \begin{document}$v$\end{document}=1). The energy distributions and product angular distributions were obtained from the CO velocity imaging. The correlated NH(\begin{document}$a^1\Delta$\end{document}) rovibrational state distributions were determined. The vibrational branching ratio of \begin{document}$^1$\end{document}NH (\begin{document}$v$\end{document}=1/\begin{document}$v$\end{document}=0) increases as the rotational state of CO(\begin{document}$v$\end{document}=0) increases initially and decreases afterwards, which indicates a special state-to-state correlation between the \begin{document}$.1$\end{document}NH and CO products. About half of the available energy was partitioned into the translational degree of freedom. The negative anisotropy parameter \begin{document}$\beta$\end{document} indicates that it is a vertical direct dissociation process.  相似文献   

20.
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