Xiamen University realizes electrochemical liquid gating technology for future air purification

On September 26, 2022, Professor Hou Xu’s team from Xiamen University published a research result entitled “Continuous Air Purification by Aqueous Interface Filtration and Absorption” in the journal Nature.

The results report the use of “responsive liquid gating technology” to propose the core mechanism of efficient filtration and absorption of different microscale particles at the water interface, which opens up the technical difficulties of filtration and absorption, antifouling and anticorrosion, antibacterial deodorization and long-term operation in the existing air purification, and provides a new idea for the design of air purifiers.

Professor Hou Xu, director of the Institute of Electrochemical Science and Engineering of Xiamen University, is the corresponding author of the paper, and doctoral student Zhang Yunmao is the first author of the paper.

In recent years, air pollution has always been an important issue of concern, and the continuous smog weather has not only increased the outbreak of respiratory diseases, but also caused serious economic and social problems. Particulate matter in air pollutants is a class of substances with greater harm, which is composed of a complex mixture of solid, liquid, organic and inorganic material particles, and the concentration of particulate matter has been used as an important indicator of air pollution. The direct and effective way to remove these particles is still to use a variety of air filtration purification systems, which are mostly composed of multi-layer fiber membranes or filter membrane units composed of porous materials. However, due to the accumulation of particles on their surface and internal pores, these filter units will inevitably suffer from clogging problems, and the dust holding capacity of their surfaces fundamentally limits the efficiency and service life of such filtration units. Therefore, such a system needs to be replaced or cleaned regularly to maintain its optimal purification performance, which will increase the complexity and maintenance cost of the system, and the replacement of accessories will also generate solid waste; At present, the perfect trade-off between purification efficiency, service life and maintenance cost is still almost insoluble, and how to develop purification systems with high purification efficiency, long service life and no complex maintenance is an important research goal in this field.

Hou Xu’s team at Xiamen University is committed to the research of biomimetic liquid-based materials and their interface science. Inspired by the biological alveolar pores, the “liquid gating mechanism” based on liquid as a structural material was first proposed by Hou Xu and others, and Hou Xu’s team gradually took concrete shape into the concept and theory development of liquid gating technology and led the global development of the technology. In 2020, liquid gating technology was named the annual “Top Ten Emerging Technologies in the Field of Chemistry” by the world’s authoritative chemical organization, the International Union of Pure and Applied Chemistry, IUPAC. Different from the concept of traditional solid porous system and liquid film system, liquid gating refers to the use of capillary force in the microscale pore to steadily fill the liquid inside the pore channel, open quickly under a certain pressure, and form a channel with a liquid layer on the inner wall of the porous material pore channel, and has reversible regulation. Its liquid layer can provide a dynamic molecular level flat interface for liquid gated materials, so it has excellent anti-fouling and energy-saving properties, which helps to solve cutting-edge scientific and application problems in materials science, chemistry, environment, biomedical engineering and other related fields.

Figure 1: Continuous and efficient air purification based on liquid gating technology

The air purification research work is the further sublimation of the liquid as a structural and functional material, the core of which is to use the electrochemical response liquid gating technology to adjust the surface wetting of the porous membrane as a solid skeleton, the specific functional liquid as a structural and functional material at the same time, electrochemical regulation of the physicochemical properties of the solid-liquid interface to achieve the control of microbubble size, and by regulating the interaction between particulate matter and liquid to control the transfer of substances on the air-water interface (Figure 2). This method converts the effective surface area used by the traditional solid material for pollutant filtration into the effective volume of the liquid material for the filtration absorption of pollutants, thereby achieving an order of magnitude increase in the amount of pollutant handling, thereby improving the purification efficiency and improving the dust capacity of the purifier. In addition, the use of gated liquid as the main filter material can be connected by pipeline, automation and programmatic control, further realizing maintenance-free, efficient and low-cost system operation. Functional fluids can also be designed as needed, giving the air purification gate system the ability to suit specific purification needs, such as antimicrobial capabilities, removal of odor and harmful gas contaminants, and corrosion resistance.

Figure 2: Schematic diagram of filtration and absorption mechanisms at the gated water interface of an electrochemically responsive liquid

The electrochemical liquid gate air purification system can also be combined with artificial intelligence technology, microfluidic technology and other integrated applications, and is expected to achieve intelligent and rapid adjustment of a variety of functional liquids in the future to meet the needs of air purification in different environments. The mechanism of multiphase interface interaction and interfacial material transport will also help to study mass transfer and chemical reactions in heterogeneous systems, which will promote the development of microreactors and research and development in catalysis, emulsification, cosmetics, pharmaceuticals and other fields.

Figure 3: Professor Hou Xu directs students’ experiments in the laboratory

The study was also supported by the team of Professor Zang Duyang of Northwestern Polytechnical University. This research work has been supported by the National Natural Science Foundation of China (52025132, 21975209, 21621091, 22021001 and 22121001), the National Key R&D Program of China (2018YFA0209500), the 111 Project (B17027, B16029) and the Fujian Energy Materials Science and Technology Innovation Laboratory Science and Technology Project (RD2022070601), Funded by the State Key Laboratory of Physical Chemistry of Solid Surfaces Science and Technology Project, Fujian Natural Science Foundation and other projects. (Source: Science Network)

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