Mathematical Model-Assisted Ultrasonic Spray Coating for Scalable Production of Large-Sized Solid Oxide Electrochemical Cells.

Thin solid oxide films are crucial for developing high-performance solid oxide-based electrochemical devices aimed at decarbonizing the global energy system. Among various methods, ultrasonic spray coating (USC) can provide the throughput, scalability, quality consistency, roll-to-roll compatibility, and low material waste necessary for scalable production of large-sized solid oxide electrochemical cells. However, due to the large number of USC parameters, systematic parameter optimization is required to ensure optimal settings. However, the optimizations in previous literature are either not discussed or not systematic, facile, and practical for scalable production of thin oxide films. In this regard, we propose an USC optimization process assisted with mathematical models. Using this method, we obtained optimal settings for producing high-quality, uniform 4 × 4 cm2 oxygen electrode films with a consistent thickness of ∼27 µm in 1 min in a facile and systematic way. The quality of the films is evaluated at both micrometer and centimeter scales and meets desirable thickness and uniformity criteria. To validate the performance of USC-fabricated electrolytes and oxygen electrodes, we employ protonic ceramic electrochemical cells, which achieve a peak power density of 0.88 W cm-2 in the fuel cell mode and a current density of 1.36 A cm-2 at 1.3 V in the electrolysis mode, with minimal degradation over a period of 200 h. These results demonstrate the potential of USC as a promising technology for scalable production of large-sized solid oxide electrochemical cells.

Antimony nanobelt asymmetric membranes for sodium ion battery.

In this study, composite asymmetric membranes containing antimony (Sb) nanobelts are prepared via a straightforward phase inversion method in combination with post-pyrolysis treatment. Sb nanobelt asymmetric membranes demonstrate improved cyclability and specific capacity as the alloy anode of sodium ion battery compared to Sb nanobelt thin films without asymmetric porous structure. The unique structure can effectively accommodate the large volume expansion of Sb-based alloy anodes, prohibit the loss of fractured active materials, and aid in the formation of stable artificial solid electrolyte interphases as evidenced by an outstanding capacity retention of ∼98% in 130 cycles at 60 mA g-1. A specific capacity of ∼600 mAh g-1is obtained at 15 mA g-1(1/40C). When the current density is increased to 240 mA g-1, ∼80% capacity can be maintained (∼480 mAh g-1). The relations among phase inversion conditions, structures, compositions, and resultant electrochemical properties are revealed through comprehensive characterization.

Metal-Free Synthesis of N-Heterocycles via Intramolecular Electrochemical C-H Aminations.

N-heterocycles are key structural units in many drugs, biologically interesting molecules and functional materials. To avoid the residues of metal catalysts, the construction of N-heterocycles under metal-free conditions has attracted much research attention in academia and industry. Among them, the intramolecular electrochemical C-H aminations arguably constitute environmentally friendly methodologies for the metal-free construction of N-heterocycles, mainly due to the direct use of clean electricity as the redox agents. With the recent renaissance of organic electrosynthesis, the intramolecular electrochemical C-H aminations have undergone much progress in recent years. In this article, we would like to summarize the advances in this research field since 2019. The emphasis is placed on the reaction design and mechanistic insight. The challenges and future developments in the intramolecular electrochemical C-H aminations are also discussed.

Revitalizing interface in protonic ceramic cells by acid etch.

Protonic ceramic electrochemical cells hold promise for operation below 600 °C (refs. 1,2). Although the high proton conductivity of the bulk electrolyte has been demonstrated, it cannot be fully used in electrochemical full cells because of unknown causes3. Here we show that these problems arise from poor contacts between the low-temperature processed oxygen electrode-electrolyte interface. We demonstrate that a simple acid treatment can effectively rejuvenate the high-temperature annealed electrolyte surface, resulting in reactive bonding between the oxygen electrode and the electrolyte and improved electrochemical performance and stability. This enables exceptional protonic ceramic fuel-cell performance down to 350 °C, with peak power densities of 1.6 W cm-2 at 600 °C, 650 mW cm-2 at 450 °C and 300 mW cm-2 at 350 °C, as well as stable electrolysis operations with current densities above 3.9 A cm-2 at 1.4 V and 600 °C. Our work highlights the critical role of interfacial engineering in ceramic electrochemical devices and offers new understanding and practices for sustainable energy infrastructures.

Protocol efficiently measuring the swelling rate of hydrogels.

Hydrogels are polymeric materials which can swell in water and retain a significant fraction of water within their structure without dissolving in water. Swelling rate is one of the most important properties of hydrogels. To measure the swelling rate, the profile of swelling capacity versus time of a hydrogel sample is obtained by performing free-absorbency capacity measurements at consecutive time intervals. Traditionally, either the tea-bag method, the sieve method, or the filtration method is used for the free-absorbency capacity measurements depending on the amount of the available sample and the desired precision. However, each method has its own systematic drawbacks. In this paper, a novel method called sieve filtration method is proposed for the measurement of the swelling rate of hydrogels. A protocol for this method is described in detail. The measurement results obtained from the proposed method and the traditional methods are compared. The proposed method has the following advantages over the traditional methods: •It is more efficient than the traditional methods due to full contact of the hydrogel powders with water or aqueous solution as well as fast and complete removal of excessive fluid from the water-absorbed gel.•It enables repeatable and reproducible measurement of the swelling rate of hydrogels.•It is easy to implement, suitable for various types of hydrogels and aqueous solutions; and it requires small amounts of sample, minimal technical skill, and inexpensive equipment.

Screening of Fungi for Potential Application of Self-Healing Concrete.

Concrete is susceptible to cracking owing to drying shrinkage, freeze-thaw cycles, delayed ettringite formation, reinforcement corrosion, creep and fatigue, etc. Continuous inspection and maintenance of concrete infrastructure require onerous labor and high costs. If the damaging cracks can heal by themselves without any human interference or intervention, that could be of great attraction. In this study, a novel self-healing approach is investigated, in which fungi are applied to heal cracks in concrete by promoting calcium carbonate precipitation. The goal of this investigation is to discover the most appropriate species of fungi for the application of biogenic crack repair. Our results showed that, despite the significant pH increase owing to the leaching of calcium hydroxide from concrete, Aspergillus nidulans (MAD1445), a pH regulatory mutant, could grow on concrete plates and promote calcium carbonate precipitation.

Fabrication of SnO2 Asymmetric Membranes for High Performance Lithium Battery Anode.

Alloy electrode material like tin dioxide (SnO2) possesses much higher specific capacity as compared to commercial graphite anode in lithium ion battery (783 vs 372 mAh g(-1)). However, the huge volume change (260%) of SnO2-based anode during the alloying and dealloying process can cause significant electrode pulverization and rapid capacity loss. Herein we report the synthesis of SnO2 asymmetric membranes via a unique combination of phase inversion and sol-gel chemistry to overcome this big challenge. The SnO2 asymmetric membrane electrode demonstrates a specific capacity of 500 mAh g(-1) based on the overall electrode mass at a current density of 280 mA g(-1) (∼0.5C) with >96% capacity retention after 400 cycles. When the current density is increased from 28 to 560 mA g(-1), its overall capacity is only reduced by 36%. Such an outstanding rate and cycling performance is attributed to the existence of networking porous structure in the membrane that can provide high electrical conductivity, multiple diffusion channels, and free volumes for electrode expansion. The carbonization temperature has a dramatic impact on the electrode performance. Membranes carbonized at 500 °C show an excellent cycling performance, whereas the capacity of the membrane carbonized at 800 °C decreases by 51% in 100 cycles. Such a drastic difference in cycle life is caused by the reduction of small SnO2 NPs (∼3.9 nm) into large metallic tin spheres (∼40 nm) at 800 °C. This is the first original report on using asymmetric membrane structure to stabilize an SnO2-based lithium ion battery anode with an excellent electrochemical performance.

On the estimation of dynamic mass density of random composites.

The dynamic effective mass density and bulk modulus of an inhomogeneous medium at low frequency limit are discussed. Random configurations in a variety of two-dimensional physical contexts are considered. In each case, effective dynamic mass density and bulk modulus are calculated based on eigenmode matching theory. The results agree with those provided by Martin et al. [J. Acoust. Soc. Am. 128, 571-577 (2010)] obtained from effective wavenumber method.

[Adrenal myelolipoma:clinical diagnosis and management of 26 cases].

OBJECTIVE: To evaluate the diagnosis and management of adrenal myelolipoma. METHODS: The clinical data of 26 cases were analyzed retrospectively and the selected articles were reviewed. There were no specific clinical symptom and endocrine abnormality, except increasing catecholamine in 2 cases. All cases but two were diagnosed by B-model ultrasound scanning (B-US), CT or magnetic resonance imaging (MRI). RESULTS: Twenty-six cases were surgically treated, the diameter of the tumor was 5 - 10 cm, simple tumor resection was performed in 16 cases, and complete adrenal resection was performed in 10 cases. All the operated cases were proved by pathologists. The duration of follow-up was from 6 - 28 months after surgery. No recurrence was observed. CONCLUSIONS: The diagnosis of adrenal myelolipoma could be established based on B-US, CT or MRI. The tumors whose diameter is larger than 5 cm in size should be removed.