The fabrication strategies, characterizations, photocatalytic performances and the corresponding mechanism of some typical TiO2/MOF composites were highlighted and reviewed. Also, the prospective and ...challenges of TiO2/MOF composites as photocatalysts were declared.
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•The facile fabrication strategies of TiO2/MOF composites were highlighted.•The enhanced photocatalytic activities of TiO2/MOF composites were reviewed.•The possible photocatalysis mechanisms over TiO2/MOF composites were summed.•The composite fabrication is a good approach to combine the merits of TiO2 and MOF.•The prospective of TiO2/MOF composites as photocatalysts is declared.
Up to now, titanium dioxide (TiO2) is the most established semiconductor photocatalyst, which is used to achieve photocatalytic H2 evolution, pollutants degradation, CO2 reduction, and N2 reduction under UV light irradiation. TiO2 as photocatalyst is always under the spotlight due to its unique properties like outstanding thermal/chemical stability, wide bandgap with suitable band edge, low cost, non-toxicity, and corrosion resistance. To further improve the photocatalytic activity of TiO2, the versatile and porous metal-organic frameworks (MOFs) can be introduced to constructionTiO2/MOF composites, which can accomplish the enhanced light absorption performance and improved electron-hole pair separation. With this review, the fabrication strategies, characterizations techniques, photocatalytic activities and the mechanisms of some selected TiO2/MOF composites were reviewed and highlighted. The last but not the least, the outlooks and challenges of TiO2/MOF composites as photocatalysts for energy conversion and environment remediation are proposed.
LiNi
Mn
Co
O
-layered cathode is often fabricated in the form of secondary particles, consisting of densely packed primary particles. This offers advantages for high energy density and alleviation of ...cathode side reactions/corrosions, but introduces drawbacks such as intergranular cracking. Here, we report unexpected observations on the nucleation and growth of intragranular cracks in a commercial LiNi
Mn
Co
O
cathode by using advanced scanning transmission electron microscopy. We find the formation of the intragranular cracks is directly associated with high-voltage cycling, an electrochemically driven and diffusion-controlled process. The intragranular cracks are noticed to be characteristically initiated from the grain interior, a consequence of a dislocation-based crack incubation mechanism. This observation is in sharp contrast with general theoretical models, predicting the initiation of intragranular cracks from grain boundaries or particle surfaces. Our study emphasizes that maintaining structural stability is the key step towards high-voltage operation of layered-cathode materials.
Cryptocurrencies, such as Bitcoin, have ignited intense discussions. Despite receiving extensive public attention, theoretical understanding is limited regarding the value of blockchain-based ...cryptocurrencies, as expressed in their exchange rates against traditional currencies. In this paper, we conduct a theory-driven empirical study of the Bitcoin exchange rate (against USD) determination, taking into consideration both technology and economic factors. To address co-integration in a mix of stationary and non-stationary time series, we use the autoregressive distributed lag (ARDL) model with a bounds test approach in the estimation. Meanwhile, to detect potential structural changes, we estimate our empirical model on two periods separated by the closure of Mt. Gox (one of the largest Bitcoin exchange markets). According to our analysis, in the short term, the Bitcoin exchange rate adjusts to changes in economic fundamentals and market conditions. The long-term Bitcoin exchange rate is more sensitive to economic fundamentals and less sensitive to technological factors after Mt. Gox closed. We also identify a significant impact of mining technology and a decreasing significance of mining difficulty in the Bitcoin exchange price determination.
•We theoretically discuss the technology and economic determinants of the Bitcoin exchange rate•We use the ARDL model with bounds test to address co-integration of a mix of stationary and non-stationary time series•We find Bitcoin exchange rate relates more with economic fundamentals and less with technology factors as Bitcoin evolves•We find the impact of computational capacities on Bitcoin is decreasing as technology progresses
Symmetry protected topological (SPT) phases are a minimal generalization of the concept of topological insulators to interacting systems. In this paper, we describe the classification and properties ...of such phases for three-dimensional (3D) electronic systems with a number of different symmetries. For symmetries representative of all classes in the famous 10-fold way of free-fermion topological insulators/superconductors, we determine the stability to interactions. By combining with results on bosonic SPT phases, we obtain a classification of electronic 3D SPT phases for these symmetries. In cases with a normal U(1) subgroup we show that this classification is complete. We describe the nontrivial surface and bulk properties of these states. In particular, we discuss interesting correlated surface states that are not captured in a free-fermion description. We show that in many, but not all, cases, the surface can be gapped while preserving symmetry if it develops intrinsic topological order.
Bifunctional Bi12O17Cl2/MIL-100(Fe) composite (BMx) was firstly constructed via facile ball-milling method. The optimal BM200 was highly efficient for Cr(VI) sequestration and activation of ...persulfate (PS) for bisphenol A (BPA) decomposition under white light illumination, which was much more remarkable than the pristine MIL-100(Fe) and Bi12O17Cl2, respectively. Furthermore, the photocatalytic reduction efficiency can be significantly improved via the addition of some green small organic acids (SOAs). As well, the BPA degradation can be achieved over an extensive initial pH range of 3.0–11.0. When the PS concentration increased to more than 2.0 mM, the BPA degradation efficiency decreased due to the SO4−• self-scavenging effect. It was also found that the co-existence of inorganic anions like H2PO4−, HCO3−, SO42−, Cl− and NO3− could decelerate the BPA degradation. The excellent photocatalytic Cr(VI) reduction and persulfate activation performances originated from both MIL-100(Fe) with excellent PS activation ability and Bi12O17Cl2 with a favorable band position, which not only enabled the efficient separation of charges but also accelerated the formation of SO4−• radicals. The BM200 displayed prominent stability and recyclability. More importantly, the credible degradation pathway was proposed based on UHPLC-MS analysis and DFT calculation. This research revealed that the Fe-based MOFs/bismuth-rich bismuth oxyhalides (BixOyXz, X = Cl, Br and I) composites possessed great potential in wastewater remediation.
Bismuth-rich Bi12O17Cl2/MIL-100(Fe) composites were firstly fabricated to achieve efficient Cr(VI) sequestration and BPA degradation with the addition of persulfate PS under white light illumination. Display omitted
•Bi12O17Cl2/MIL-100(Fe) (BMx) was constructed by facile ball-milling method.•BM200 composite was an efficient photocatalyst for Cr(VI) and BPA cleanup.•BM200/light/PS system exhibited synergistic effect in BPA degradation.•BM200 showed good reusability and high stability.•DFT calculation with high Fukui index interpreted the easy-attacking sites on BPA.
Today East Asia harbors many "relict" plant species whose ranges were much larger during the Paleogene-Neogene and earlier. The ecological and climatic conditions suitable for these relict species ...have not been identified. Here, we map the abundance and distribution patterns of relict species, showing high abundance in the humid subtropical/warm-temperate forest regions. We further use Ecological Niche Modeling to show that these patterns align with maps of climate refugia, and we predict species' chances of persistence given the future climatic changes expected for East Asia. By 2070, potentially suitable areas with high richness of relict species will decrease, although the areas as a whole will probably expand. We identify areas in southwestern China and northern Vietnam as long-term climatically stable refugia likely to preserve ancient lineages, highlighting areas that could be prioritized for conservation of such species.
For broad-spectrum adsorption and capture toward cationic metal ions, a facile strategy was adopted to fabricate defective SO3H-MIL-101(Cr) (SS-SO3H-MIL-101(Cr)-X, X = 2, 3, 4) with enhanced ...vacancies using seignette salt (SS) as the modulating agent. The boosted adsorption performances of SS-SO3H-MIL-101(Cr)-X toward eight different ions, including Ag+, Cs+, Pb2+, Cd2+, Ba2+, Sr2+, Eu3+ and La3+ in both individual component and mixed component systems, could be ascribed to the effective mass transfer resulting from the exposure of defective sites. Especially, the optimal SS-SO3H-MIL-101(Cr)−3 could remove all the selected metal cations to below the permissible limits required by the World Health Organization (WHO) in the continuous-flow water treatment system. Furthermore, SS-SO3H-MIL-101(Cr)−3 exhibited good adsorption capacity (189.6 mg·g−1) toward Pb2+ under neutral condition and excellent desorption recirculation performance (removal efficiency > 95% after 5 cycles). Moreover, the adsorption mechanism involved the electrostatic adsorption and coordinative interactions resulting from complexation between the adsorption active sites and targeted cations (like Cr-O-M and S-O-M), which were explored systematically via both X-ray photoelectron spectroscopy (XPS) determination and density functional theory (DFT) calculations. Overall, this work provided guidance for modulating SS-SO3H-MIL-101(Cr)-X to promote its potential application in widespread metal cations removal from wastewater.
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•Defective SO3H-MIL-101(Cr) with abundant vacancies was obtained.•SS-SO3H-MIL-101(Cr)-X exhibited adsorption activity toward various metal cations.•The sorption mechanisms were clarified via characterizations and DFT calculations.
Social-networking functions are increasingly embedded in online rating systems. These functions alter the rating context in which consumer ratings are generated. In this paper, we empirically ...investigate online friends’ social influence in online book ratings. Our quasi-experimental research design exploits the temporal sequence of social-networking events and ratings and offers a new method for identifying social influence while accounting for the homophily effect. We find that rating similarity between friends is significantly higher after the formation of the friend relationship, indicating that with social-networking functions, online rating contributors are socially nudged when giving their ratings. Exploration of contingent factors suggests that social influence is stronger for older books and for users who have smaller networks, and that relatively more recent and extremely negative ratings cast more salient influence.
The online appendix is available at
https://doi.org/10.1287/isre.2017.0741
.
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•CoM/TNTs showed high ACE degradation efficiency after PMS activation.•Efficient PMS activation was due to the synergic effect of Co(OH)2 and TNTs.•TNTs with abundant surface –OH ...facilitated formation of CoOH+.•PES analysis well explained the higher feasibility of Co(OH)+ on PMS activation.•ACE atoms with high Fukui index are active sites for electrophilic attack.
Pharmaceuticals and personal care products (PPCPs) are of great concern due to their increasing health effects, so advanced treatment technologies for PPCPs removal are urgently needed. In this study, titanate nanotubes decorated Co(OH)2 hollow microsphere (CoM/TNTs) composites were synthesized by a two-step solvothermal method, and used to activate peroxymonosulfate (PMS) through heterogenous catalysis for acetaminophen (ACE) degradation in water. The optimum material (CoM/TNTs0.5) activated PMS system exhibited high ACE removal efficiency and quick kinetic, as 93.0% ACE was degraded even within 10 min. The two components in CoM/TNTs showed a synergetic effect on PMS activation for radicals production: Co(OH)+ from CoM was the primary active species to active PMS, while TNTs could offer abundant –OH groups for Co(OH)+ formation. Density functional theory (DFT) calculation further interpreted the mechanism of Co(OH)+ for PMS activation by means of reaction potential energy surface (PES) analysis. Both the scavenger quenching tests and electron paramagnetic resonance analysis revealed that the sulfate radical (SO4-·) played a dominant role in ACE degradation. Moreover, DFT calculation also suggested that the ACE atoms with high Fukui index (f-) represented the active sites for electrophilic attack by SO4-·. The toxicity analysis based on quantitative structure-activity relationship (QSAR) verified the reduced toxicity of transformation products. Furthermore, CoM/TNTs also had good reusability and stability over five cycles. This work provides deep insights into the reaction mechanisms of radical production and organics attack in cobalt-based PMS activation system.
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