Metallic Zn as a promising anode material of aqueous batteries suffers from severe parasitic reactions and notorious dendrite growth. To address these issues, the desolvation and nucleation processes ...need to be carefully regulated. Herein, Zn foils coated by ZnF2–Ag nanoparticles (ZnF2–Ag@Zn) are used as a model to modulate the desolvation and nucleation processes by hybrid surfaces, where Ag has a strong affinity to Zn adatoms and ZnF2 shows an intense adsorption to H2O. This selective adsorption of different species on ZnF2 and Ag reduces the mutual interference between two species. Therefore, ZnF2–Ag@Zn exhibits the electrochemical performance much better than ZnF2@Zn or Ag@Zn. Even at −40 °C, the full cells using ZnF2–Ag@Zn demonstrate an ultralong lifespan of 5000 cycles with a capacity retention of almost 100%. This work provides new insights to improve the performance of Zn metal batteries, especially at low temperatures.
Flexible and light‐weight solar cells are important because they not only supply power to wearable and portable devices, but also reduce the transportation and installation cost of solar panels. ...High‐efficiency organometal halide perovskite solar cells can be fabricated by a low‐temperature solution process, and hence are promising for flexible‐solar‐cell applications. Here, the development of perovskite solar cells is briefly discussed, followed by the merits of organometal halide perovskites as promising candidates as high‐efficiency, flexible, and light‐weight photovoltaic materials. Afterward, recent developments of flexible solar cells based on perovskites are reviewed.
Organometal halide perovskites are promising photovoltaic materials for flexible and light‐weight solar cells. The high power conversion efficiency (over 15%) of flexible perovskite solar cells is not only useful to power wearable and portable devices, but also promising for off‐grid and on‐grid photovoltaic applications. Recent progress in flexible perovskite solar cells is discussed.
Light‐emitting diodes (LEDs) based on solution‐processed metal halide perovskites have shown great application potential in energy‐efficient lighting and displays. Multiple‐quantum‐well (MQW) ...perovskites simultaneously possess high photoluminescence quantum efficiency and good film morphology and stability, making it attractive for high‐performance perovskite LEDs. Here, merits of MQW perovskites and the progress in MQW perovskite LEDs are reviewed. Challenges and future directions of perovskite LEDs are also discussed.
Solution‐processed multiple quantum well (MQW) perovskites are assemblies of different layered metal‐halide perovskites that are considered promising toward achieving efficient and stable perovskite light‐emitting diodes (LEDs) due to good morphology, high photoluminescence quantum efficiency, and good stability. The recent progress in MQW perovskite LEDs is discussed.
The epidemic of 2019 novel coronavirus, later named as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is still gradually spreading worldwide. The nucleic acid test or genetic ...sequencing serves as the gold standard method for confirmation of infection, yet several recent studies have reported false-negative results of real-time reverse-transcriptase polymerase chain reaction (rRT-PCR). Here, we report two representative false-negative cases and discuss the supplementary role of clinical data with rRT-PCR, including laboratory examination results and computed tomography features. Coinfection with SARS-COV-2 and other viruses has been discussed as well.
•Dopant distribution of modified Fe2O3 and Fe3O4 was studied.•Surface structures of modified Fe2O3 and Fe3O4 were analyzed.•An efficient computational methodology was proposed for initial dopant ...screening.
Enhancing the deep reduction of Fe2O3 oxygen carriers (OCs) is a major challenge in the chemical looping hydrogen production (CLH) process. To solve this issue, the modification of Fe2O3 OCs by introducing foreign dopant is an effective strategy. Here, we propose a dopant screening scheme, where surface oxygen vacancy formation energy (Evac) is defined as a descriptor for the reducibility of modified Fe2O3 OCs. Using density functional theory (DFT) calculations, we evaluated the 18 potential dopants, including 3 alkali metals (Li, Na, and K), 2 alkaline earth metals (Mg and Ca), 11 transition metals (Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Y, and Zr), and 2 rare earth metals (La and Ce). The results indicated that Li, Na, K, Mg, Ni, Cu, Zn, La, and Zr dopants, which not only significantly enhance the reduction reaction from Fe2O3 to Fe3O4 but improve the deep reduction from Fe3O4 to FeO, are screened as the promising candidates for modified Fe2O3 OCs in the CLH process. Our work provided an efficient approach for the initial screening of modified Fe2O3 OCs with enhanced deep reducibility.
Symmetries play very important roles in the dynamics of electrical systems. The relevant electronic circuits with fault diagnostics, including the optimized neural network algorithm model, are ...designed on the basis of symmetry principles. In order to improve the efficiency of the circuit pressure test, a circuit pressure function equivalent compression test method based on the parallel neural network algorithm is proposed. For the implementation stage of the circuit pressure test, the improved modified node algorithm (MNA) is used to build an optimization model, and the circuit network is converted into an ordinary differential equation for the circuit pressure function equivalent compression test. The test aims to minimize flux. Then, backpropagation (BP) neural network algorithm data fusion is introduced to optimize the minimum flux model of the cyclic pressure functional equivalent compression test. Finally, a simulation experiment is carried out to verify the effectiveness of the algorithm in the accuracy and efficiency of the pressure test. The results show that the improved BP neural network improves the data fusion accuracy and shortens the sample training time; compared with the uncompressed algorithm, the running time of the proposed algorithm is greatly reduced and the execution efficiency is high; compared with the vascular pressure test method, there is no significant difference in the convergence accuracy and it is at a level of 10−5. Since the parallel computing problem is not considered in either of the two-pulse tube pressure test methods, the convergence time of the algorithm increases exponentially with the increase in the number of parallel threads. However, the algorithm in this research considers the problem of parallel execution and uses a quad-core processor, with no significant change in computing time and high computing efficiency. Therefore, BP neural network data fusion can be used for the fault diagnosis of electronic circuits, with a high operating efficiency and good development prospects.
Increasing the energy density of lithium-sulfur batteries necessitates the maximization of their areal capacity, calling for thick electrodes with high sulfur loading and content. However, ...traditional thick electrodes often lead to sluggish ion transfer kinetics as well as decreased electronic conductivity and mechanical stability, leading to their thickness-dependent electrochemical performance. Here, free-standing and low-tortuosity N, O co-doped wood-like carbon frameworks decorated with carbon nanotubes forest (WLC-CNTs) are synthesized and used as host for enabling scalable high-performance Li-sulfur batteries. EIS-symmetric cell examinations demonstrate that the ionic resistance and charge-transfer resistance per unit electro-active surface area of S@WLC-CNTs do not change with the variation of thickness, allowing the thickness-independent electrochemical performance of Li-S batteries. With a thickness of up to 1200 µm and sulfur loading of 52.4 mg cm
, the electrode displays a capacity of 692 mAh g
after 100 cycles at 0.1 C with a low E/S ratio of 6. Moreover, the WLC-CNTs framework can also be used as a host for lithium to suppress dendrite growth. With these specific lithiophilic and sulfiphilic features, Li-S full cells were assembled and exhibited long cycling stability.
Quasi‐2D layered organometal halide perovskites have recently emerged as promising candidates for solar cells, because of their intrinsic stability compared to 3D analogs. However, relatively low ...power conversion efficiency (PCE) limits the application of 2D layered perovskites in photovoltaics, due to large energy band gap, high exciton binding energy, and poor interlayer charge transport. Here, efficient and water‐stable quasi‐2D perovskite solar cells with a peak PCE of 18.20% by using 3‐bromobenzylammonium iodide are demonstrated. The unencapsulated devices sustain over 82% of their initial efficiency after 2400 h under relative humidity of ≈40%, and show almost unchanged photovoltaic parameters after immersion into water for 60 s. The robust performance of perovskite solar cells results from the quasi‐2D perovskite films with hydrophobic nature and a high degree of electronic order and high crystallinity, which consists of both ordered large‐bandgap perovskites with the vertical growth in the bottom region and oriented small‐bandgap components in the top region. Moreover, due to the suppressed nonradiative recombination, the unencapsulated photovoltaic devices can work well as light‐emitting diodes (LEDs), exhibiting an external quantum efficiency of 3.85% and a long operational lifetime of ≈96 h at a high current density of 200 mA cm−2 in air.
High‐crystallinity quasi‐2D perovskite films with oriented structure are fabricated by using 3‐bromobenzylammonium iodide, leading to perovskite solar cells with a high efficiency of 18.20%. Moreover, the unencapsulated devices exhibit excellent moisture resistance, retaining 82% of the initial efficiency after 2400 h under ambient conditions. Even after immersion into water for 60 s, the unsealed device shows little decay.
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