Antibiotics have been widely used to treat bacterial diseases. Their wide spread in ecological environment will induce generation of antibiotic-resistant bacteria Therefore, it is critical to create an eco-friendly and effective approach for their removal. Herein, a bimetallic sulfide FeS2@MoS2 with rich sulfur vacancies (SVs) and high percentage of metallic 1T phase MoS2 was prepared by one-step solvothermal method to degrade ofloxacin (OFX) by activated peroxymonosulfate (PMS). FeS2@MoS2-1 (the mass ratio of Fe/Mo is 1) exhibited excellent performance for PMS activation, with 99.26% OFX removed in 20 min (0.2 g/L FeS2@MoS2-1, 0.2 mM PMS, initial pH). The degradation rate constant of kobs was 0.21 min−1 with FeS2@MoS2-1 system, which was about 4.88 and 22.91 times of FeS2/PMS and MoS2/PMS systems under the same experimental conditions respectively. In FeS2@MoS2-1, besides S2−, SVs would also accelerate Fe(III)/Fe(II) circulation through increasing the exposure of Mo(IV) active sites. Additionally, MoS2 transferred from the semi-conductive 2H phase to the metallic 1T phase, which could speed up electron transfer rate significantly. Quenching experiment and EPR test showed that SO4− and O2− were the main active oxygen species. Degradation pathway was proposed through the active sites identification by DFT calculations and intermediates detection by HPLC-MS analyzation. The results showed that OFX were vulnerable to be attacked and broke to form small molecular compounds through hydrogen loss, oxidative cracking, decarboxylation and demethylation four ways. In addition, their bio-toxicity was investigated and results showed that the toxic was diminished. This work indicated that the satisfactory universality, recyclability and stability enabled FeS2@MoS2-1 could be used as an efficient catalyst to activate PMS to degrade refractory organic pollutants in water.
The rapid development of high-speed rail has markedly shortened the travel time from one city to another. However, the impact of space–time compression brought about by high-speed rail on city innovation has not received sufficient attention. This paper examines the space–time compression phenomenon produced by high-speed railway networks and its impact on city innovation from 2000 to 2019 using a sample of 279 Chinese prefecture-level cities. The empirical results show that there was a strong space–time compression during this period. The development of high-speed rail can promote city innovation. However, the construction of high-speed rail also produces a siphon effect, which accelerates the convergence of innovative elements in cities with stronger innovation capabilities. Nevertheless, it has a negative spillover effect on cities with weaker innovation capabilities. Finally, policy recommendations for promoting the balanced development of city innovation and recommendations for future research are presented.
Governmental investment in commercializing academic patents has spurred economic growth. This study explores the mechanism underlying the impact of academic patent commercialization on regional economic development based on holistic view of the integration of local and neighbourhood hierarchies. The empirical analysis of a sample of 31 Chinese provinces from 2010 to 2019 shows that fiscal expenditures on science and technology mediate the relationship between academic patent commercialization and economic development. Moreover, there is a positive spatial spill over effect between developing economies of neighbouring provinces. In the knowledge economy era, academic patent commercialization, supported by fiscal expenditure, plays an increasingly important role in regional economic growth.
Realizing efficient hydrogenation of N2 molecules in the electrocatalytic nitrogen reduction reaction (NRR) is crucial in achieving high activity at a low potential because it theoretically requires a higher equilibrium potential than other steps. Analogous to metal hydride complexes for N2 reduction, achieving this step by chemical hydrogenation can weaken the potential dependence of the initial hydrogenation process. However, this strategy is rarely reported in the electrocatalytic NRR, and the catalytic mechanism remains ambiguous and lacks experimental evidence. Here, we show a highly efficient electrocatalyst (ruthenium single atoms anchored on graphdiyne/graphene sandwich structures) with a hydrogen radical-transferring mechanism, in which graphdiyne (GDY) generates hydrogen radicals (H•), which can effectively activate N2 to generate NNH radicals (•NNH). A dual-active site is constructed to suppress competing hydrogen evolution, where hydrogen preferentially adsorbs on GDY and Ru single atoms serve as the adsorption site of •NNH to promote further hydrogenation of NH3 synthesis. As a result, high activity and selectivity are obtained simultaneously at −0.1 V versus a reversible hydrogen electrode. Our findings illustrate a novel hydrogen transfer mechanism that can greatly reduce the potential and maintain the high activity and selectivity in NRR and provide powerful guidelines for the design concept of electrocatalysts.
Sodium chloride is expected to be found on many of the surfaces of icy moons like Europa and Ganymede. However, spectral identification remains elusive as the known NaCl-bearing phases cannot match current observations, which require higher number of water of hydration. Working at relevant conditions for icy worlds, we report the characterization of three “hyperhydrated” sodium chloride (SC) hydrates, and refined two crystal structures [2NaCl·17H 2 O (SC8.5); NaCl·13H 2 O (SC13)]. We found that the dissociation of Na + and Cl − ions within these crystal lattices allows for the high incorporation of water molecules and thus explain their hyperhydration. This finding suggests that a great diversity of hyperhydrated crystalline phases of common salts might be found at similar conditions. Thermodynamic constraints indicate that SC8.5 is stable at room pressure below 235 K, and it could be the most abundant NaCl hydrate on icy moon surfaces like Europa, Titan, Ganymede, Callisto, Enceladus, or Ceres. The finding of these hyperhydrated structures represents a major update to the H 2 O–NaCl phase diagram. These hyperhydrated structures provide an explanation for the mismatch between the remote observations of the surface of Europa and Ganymede and previously available data on NaCl solids. It also underlines the urgent need for mineralogical exploration and spectral data on hyperhydrates at relevant conditions to help future icy world exploration by space missions.
Herein, electro-catalysis (EC) as the electron donor to accelerate the continuable Fe(III)/Fe(II) cycles in different inorganic peroxides (i.e., peroxymonosulfate (PMS), peroxydisulfate (PDS) and hydrogen peroxide (HP)) activation systems were established. These electro-cocatalytic Fenton-like systems exhibited an excellent degradation efficiency of sulfamethoxazole (SMX). A series of analytical and characterization methods including quenching experiments, probe experiments, and electron paramagnetic resonance spectrometry (EPR) were implemented to systematically sort out the source and yield of reactive oxygen species (ROS). A wide kind of ROS including hydroxyl radical (•OH), singlet oxygen (1O2), and sulfate radical (SO4•−), which contributed 38%, 37%, and 24% were produced in EC/Fe(III)/PMS system, respectively. •OH was the dominant ROS in both EC/Fe(III)/PDS and EC/Fe(III)/HP processes. According to the analysis of SMX degradation routes and biotoxicity, abundant degradation pathways were identified in EC/Fe(III)/PMS process and lower environmental impact was achieved in EC/Fe(III)/HP process. The diversiform ROS of EC/Fe(III)/PMS system makes it exhibit greater environmental adaptability in complex water matrixes and excellent low-energy consumption performance in many organic pollutants degradation. Continuous flow treatment experiments proved that the three systems have great sustainability and practical application prospect. This work provides a strong basis for constructing suitable systems to achieve different treatment requirements.