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.

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.