Boron-Doped Ti3C2Tx MXene for Effective and Durable High-Current-Density Ammonia Synthesis.

Ammonia (NH3) synthesis via the nitrate reduction reaction (NO3RR) offers a competitive strategy for nitrogen cycling and carbon neutrality; however, this is hindered by the poor NO3RR performance under high current density. Herein, it is shown that boron-doped Ti3C2Tx MXene nanosheets can highly efficiently catalyze the conversion of NO3RR-to-NH3 at ambient conditions, showing a maximal NH3 Faradic efficiency of 91% with a peak yield rate of 26.2 mgh-1 mgcat. -1, and robust durability over ten consecutive cycles, all of them are comparable to the best-reported results and exceed those of pristine Ti3C2Tx MXene. More importantly, when tested in a flow cell, the designed catalyst delivers a current density of ‒1000 mA cm-2 at a low potential of ‒1.18 V versus the reversible hydrogen electrode and maintains a high NH3 selectivity over a wide current density range. Besides, a Zn-nitrate battery with the catalyst as the cathode is assembled, which achieves a power density of 5.24 mW cm-2 and a yield rate of 1.15 mgh-1 mgcat. -1. Theoretical simulations further demonstrate that the boron dopants can optimize the adsorption and activation of NO3RR intermediates, and reduce the potential-determining step barrier, thus leading to an enhanced NH3 selectivity.

Assessment of radiation dose hazards caused by radon and its progenies in tap water by the human dosimetric model.

Radon is readily soluble in water, and radon exposure caused by household water consumption may pose a threat to public health. In this study, the radon concentration in the tap water of residential buildings was measured, and the average value was 543.33 mBq L-1, which was in line with the radon concentration limit recommended by USEPA (11.11 Bq L-1) and EURATOM (100 Bq L-1), and also within the range of the results of radon concentration measurements in tap water in other countries or regions. Through water bath heating at different temperatures, the radon retention curves of multiple groups of samples at different temperatures were fitted and analyzed. The results showed that the radon retention continued to decrease between 25 and 70 °C, remained stable between 70 and 85 °C, and then continued to decline slowly. Combined with the measurement results, the effective doses of α- and ß-particles emitted by 222Rn and its progenies to residents respiratory and alimentary tissues and organs were calculated using the computational model provided by ICRP under two typical water scenarios of shower and drinking water, and the results show that radon exposure caused by normal water consumption will not pose a serious threat to public health.

Assessment of natural radioactivity and consequent radiological hazard in different brands of commercialized bottled mineral water produced in China.

As one of the drinking water quality parameters, natural radioactivity parameters are recommended to prevent a potential health threat to the public. In this study, the gross-α and gross-ß activity concentrations in 15 different brands of commercial bottled mineral water consumed in China were analyzed to evaluate the quality and corresponding health impact on the population. The activity concentrations of gross-α and gross-ß in different samples varied from 4.4 to 130.6 and 17.3-320.3 mBq L-1, respectively. The values of the annual effective dose equivalent rate (AED) for infants, children and adults ranged from 1.3 to 21.6, 2.9-52.5 and 5.5-97.8 µSv y-1, respectively. The average excess lifetime cancer risk caused by the consumption of bottled mineral water samples was estimated as 6.0 × 10-5. These results show that all the measured gross-α and gross-ß are found to be obviously less than the guidance level by WHO and the domestic standard. The values of AED are below the World Health Organization (WHO) recommended limit of 0.1 mSv y-1. Combined with the lifetime cancer risk assessment, it is concluded that there is no significant risk for consumption of the observed brands of bottled mineral water and it can be consumed safely.

Elucidating the restructuring-induced highly active bimetallic Pt-Co/KL catalyst for the aromatization of n-heptane.

A bimetallic Pt-Co/KL catalyst was fabricated via the atomic layer deposition (ALD) method and demonstrated to be highly active and stable for the aromatization of n-heptane at a low temperature (420 °C), which is due to the restructured Pt-Co clusters providing unique catalytic sites and the enhanced electron-donating properties of the catalyst.

Hybrid Fullerene-Based Electron Transport Layers Improving the Thermal Stability of Perovskite Solar Cells.

The structure-dependent thermal stability of fullerene electron transport layers (ETLs) and its impact on device stability have been underrated for years. Based on cocrystallographic understanding, herein, we develop a thermally stable ETL comprising a hybrid layer of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and [6,6]-phenyl-C61-propylbenzene (PCPB). By tuning the weight ratios of PCBM and PCPB to influence the noncovalent intermolecular interactions and packing of fullerene derivatives, we obtained a champion device based on the 20PCPB (20 wt % addition of PCPB into the mixture of PCBM/PCPB) ETL and excellent thermal stability of 500 h under 85 °C thermal aging in a N2 atmosphere in the dark. The present work exemplifies that cocrystallography can be a precise tool to probe the interaction and aggregation of fullerene derivatives in ETLs, and mixed fullerene derivatives can be sought as promising ETLs to enhance the long-term stability of perovskite solar cells under high-temperature working environments.

Highly Dispersed Single-Atom Pt and Pt Clusters in the Fe-Modified KL Zeolite with Enhanced Selectivity for n-Heptane Aromatization.

Conversion of straight-chain paraffins into aromatics is particularly attractive but extremely challenging in the oil refining industry. Constructing the Pt-supported catalysts with high aromatic selectivity is vital. Here, we report a strategy to use Fe-modified KL zeolites to improve the Pt atom utilization efficiency and anchor them inside KL zeolite channels via atomic-layer deposition technique. A combination of highly dispersed single-atom Pt and electron-rich Pt clusters is fabricated on the KL zeolite through the creation of proper nucleation sites. The resulted catalyst (PtFe-1/KL) exhibits excellent performance for the n-heptane aromatization (90.1% aromatic selectivity) with an apparent activation energy of 131 kJ/mol and much enhanced stability at a relatively lower temperature (420 °C). Experimental analysis and density functional theory calculation demonstrate that the single-atom Pt might play a key role in the initial dehydrogenation of n-heptane to 1-heptene, and the superior stable Pt clusters encapsulated inside Fe-decorated KL zeolite channels accelerate the 1-heptene dehydrocyclization to aromatics. The synergetic interaction between single-atom Pt and Pt clusters enables the PtFe-1/KL catalyst to be one of the most effective n-heptane aromatization catalysts reported to date.

Enhancing Performance and Uniformity of Perovskite Solar Cells via a Solution-Processed C70 Interlayer for Interface Engineering.

Although some kinds of semiconductor metal oxides (SMOs) have been applied as electron selective layers (ESLs) for planar perovskite solar cells (PSCs), electron transfer is still limited by low electron mobility and defect film formation of SMO ESLs fabricated via low-temperature solution process. Herein, the C70 interlayer between TiO2 and (HC(NH2)2PbI3)x(CH3NH3PbCl3)1-x is prepared by spin-coating and low-temperature annealing for planar n-i-p PSCs. The resultant TiO2/C70 ESL shows good surface morphology, efficient electron extraction, and facilitation of high-quality perovskite film formation, which can be attributed to the suitable nanosize and the superior electronic property of C70 molecules. In comparison with pristine TiO2-based PSCs, the efficiency and hysteresis index are, respectively, enhanced 28% and reduced 76% by adding the C70 interlayer between TiO2 and perovskite on the basis of statistical data of more than 50 cells. With the main advantages of low-temperature process and optimized interface, the champion efficiency of PSCs on flexible substrates could exceed 12% in contrast with the above 18% on rigid substrate.

Free-Standing Thin Webs of Activated Carbon Nanofibers by Electrospinning for Rechargeable Li-O2 Batteries.

Free-standing activated carbon nanofibers (ACNF) were prepared through electrospinning combining with CO2 activation and then used for nonaqueous Li-O2 battery cathodes. As-prepared ACNF based cathode was loosely packed with carbon nanofibers complicatedly overlapped. Owing to some micrometer-sized pores between individual nanofibers, relatively high permeability of O2 across the cathode becomes feasible. Meanwhile, the mesopores introduced by CO2 activation act as additional nucleation sites for Li2O2 formation, leading to an increase in the density of Li2O2 particles along with a size decrease of the individual particles, and therefore, flake-like Li2O2 are preferentially formed. In addition, the free-standing structure of ACNF cathode eliminates the side reactions about PVDF. As a result, the Li-O2 batteries with ACNF cathodes showed increased discharge capacities, reduced overpotentials, and longer cycle life in the case of full discharge and charge operation. This provides a novel pathway for the design of cathodes for Li-O2 battery.

Lithium Sulfur Primary Battery with Super High Energy Density: Based on the Cauliflower-like Structured C/S Cathode.

The lithium-sulfur primary batteries, as seldom reported in the previous literatures, were developed in this work. In order to maximize its practical energy density, a novel cauliflower-like hierarchical porous C/S cathode was designed, for facilitating the lithium-ions transport and sulfur accommodation. This kind of cathode could release about 1300 mAh g(-1) (S) capacity at sulfur loading of 6 ~ 14 mg cm(-2), and showed excellent shelf stability during a month test at room temperature. As a result, the assembled Li-S soft package battery achieved an energy density of 504 Wh kg(-1) (654 Wh L(-1)), which was the highest value ever reported to the best of our knowledge. This work might arouse the interests on developing primary Li-S batteries, with great potential for practical application.

Carbon-Free CoO Mesoporous Nanowire Array Cathode for High-Performance Aprotic Li-O2 Batteries.

Although various kinds of catalysts have been developed for aprotic Li-O2 battery application, the carbon-based cathodes are still vulnerable to attacks from the discharge intermediates or products, as well as the accompanying electrolyte decomposition. To ameliorate this problem, the free-standing and carbon-free CoO nanowire array cathode was purposely designed for Li-O2 batteries. The single CoO nanowire formed as a special mesoporous structure, owing even comparable specific surface area and pore volume to the typical Super-P carbon particles. In addition to the highly selective oxygen reduction/evolution reactions catalytic activity of CoO cathodes, both excellent discharge specific capacity and cycling efficiency of Li-O2 batteries were obtained, with 4888 mAh gCoO(-1) and 50 cycles during 500 h period. Owing to the synergistic effect between elaborate porous structure and selective intermediate absorption on CoO crystal, a unique bimodal growth phenomenon of discharge products was occasionally observed, which further offers a novel mechanism to control the formation/decomposition morphology of discharge products in nanoscale. This research work is believed to shed light on the future development of high-performance aprotic Li-O2 batteries.

Transfer of Ephedra genomic DNA to yeasts by ion implantation.

The genomic DNA from Ephedra glauca was randomly transferred to Saccharomyces cerevisiae and Hansenula anomala by argon and nitrogen ion implantation. Through repeated subculturing and using reversed phase high-performance liquid chromatography analysis to quantify the concentrations of the secondary metabolites, l-ephedrine and d-pseudoephedrine, 12 recombinant strains of genetically stable yeast were obtained, each using glucose as a carbon source, NaNO3 as a nitrogen source and producing l-ephedrine and/or d-pseudoephedrine. After culturing in liquid medium for 72 h, extracellular l-ephedrine and d-pseudoephedrine concentrations of 18.85 and 4.11 mg/L, respectively, were detected. Using l-ephedrine and d-pseudoephedrine as the target products, the transformation efficiencies of the genomic DNA from E. glauca transferred to S. cerevisiae and H. anomala were 1.15% (1/87) and 2.13% (8/376), respectively. The addition of the amino acid, L-Phe, to culture media substantially changed the amount of l-ephedrine and/or d-pseudoephedrine produced by the recombined yeasts. However, the change in metabolite production was not consistent among strains, rising in some, while dropping to nondetectable levels in others. After random amplification of polymorphic DNA (RAPD) analysis, four RAPD primers were obtained from the initial 100 RAPD primers, each amplifying different fragments with the recombined yeast Ar_Han0458 genome. Using one primer as polymerase chain reaction primer, the result showed that the recombined yeast Ar_Han0458 genome matched E. glauca genomic DNA at 150 bp, indicating a successful transfer of genetic information, facilitated by ion implantation.