Research Area

Overview of research

Our aim is to drive technological advancements towards a sustainable future, leveraging our extensive material knowledge. Nanosheet materials have unique electrical, chemical, and physical properties based on their crystal structure and constituent elements. 2D materials with high surface area and porous structure are considered ideal for applications such as separation processes, catalysts, adsorbents, membranes, etc. Unlike 3-dimensional functional particles, 2D materials can be easily formed into ultra-thin films due to their flat structure. We are exploring new synthesis methods, mass production techniques, and characterizing 2D materials, with the goal of developing new applications, especially in energy-environment related devices.

Chemistry for new 2D materials

Graphene can be produced in large scale through mechanical exfoliation of natural flakes, but lacks pores in its basal plane, limiting its ability to separate ions and gases. Porous structures with atomic pores are ideal for creating high-performance gas and RO membranes. However, typical porous materials such as MOFs and zeolites have isotropic particle shapes and are difficult to use in practical membrane applications and thin film fabrication. Converting these 3D structures into nanosheet form is crucial for producing high-performance functional thin films. Although there are over 50,000 MOFs and 200 zeolites, only a few nanosheet structures have been reported. Our goal is to develop a new synthesis method to convert these abundant 3D materials into 2D shapes, and to control key material characteristics such as aspect-ratio, pore-size, thickness, crystal structure, and surface functionality. Most importantly, the new materials must be produced in bulk scale for practical and industrial use.

Extremely thin membrane for separation

The separation process has been explored in various fields with different separation objectives. Distillation, chemical absorption, and physical adsorption are commercially available techniques. However, membrane separation is being adopted globally due to its economical benefits of improved energy efficiency and low installation cost. To develop a better membrane, it's essential to produce a defect-free thin film with a nanometer-level thickness and the ability to produce atomic pores of a specific size. Our group uses stacked 2D materials to create an ultra-thin selective layer on a porous support for gas separation, nanofiltration, and desalination. The thinness of the selective layer leads to dramatically improved permeation of molecules, surpassing previous polymer-based membranes. Currently, we focus on carbon-based membranes for reverse osmosis, nanofiltration, and battery separators, while exploring new 2D material structures for gas separation.

2D material/polymer composite for gas separation

The primary benefit of porous nanosheets is their ultra-thin thickness compared to traditional porous materials like zeolites and MOFs. The high aspect ratio makes it possible to create thin films with a nanometer-scale thickness. Porous nanosheets have the potential to create high-performance membranes through combining with polymers or 2D materials like graphene. The addition of a sheet with an aspect ratio of 1000 to a polymer at a concentration of 10% or higher is believed to result in a high-performance membrane comparable to a continuous crystal membrane.

2D materials for ion recovery

The demand for Li-ion batteries (LIB) is growing due to the increase in eco-friendly vehicles, leading to an increase in spent batteries. LIBs contain toxic substances that can cause environmental pollution if not properly disposed. To address this, recovery of these ions is being explored as a new resource, but traditional recovery methods are expensive. Our group is focused on developing 2D material-based membranes with high ion selectivity to reduce energy demand and make recovery more efficient. This will be achieved through modification of channel size and functional groups.

Carbon nanotubes for energy device applications

Carbon nanotubes (CNTs) are being utilized as key materials in various energy systems due to their excellent electrical and mechanical properties. Developing dispersion, modification, and shaping technologies is essential to unlock the full potential of CNTs and expand their range of energy system applications. CNTs are highly cohesive, making it difficult to disperse them uniformly, which leads to poor performance of composite materials. Therefore, the development of uniform dispersion technology is essential to unleash the unique properties of CNTs. In addition, modification technology, which introduces various functional groups on the surface of CNTs to increase their binding to other materials and impart properties tailored to specific applications, improves the dispersibility of CNTs and maximizes their performance by increasing their binding to desired materials. In addition, forming technologies that process CNTs into different forms (films, fibers, composites, etc.) are important for expanding their practical applications.

These technological developments will play an important role in improving the performance of fuel cells and accelerating their commercialization. Electrode particle coating with CNTs improves the electrical conductivity and stability of the electrode, while catalyst coating maximizes the catalyst active surface area to increase the reaction efficiency of the fuel cell. In addition, the high electrical conductivity of CNTs enables their application in the collector and gas diffusion layer of fuel cells, contributing to improved fuel cell performance. The development of CNT dispersion, modification, and forming technologies is a key enabling technology for the performance improvement and commercialization of not only fuel cells, but also various energy systems such as lithium-ion batteries, capacitors, and hydrogen storage systems. With continued research and development, CNT-based energy technologies will contribute significantly to the development of the future energy industry.

Fuel cell/Ion-exchange membranes/Electro-catalysis

Proton exchange membrane fuel cells (PEMFCs) generate electricity by converting the chemical energy of hydrogen through a proton exchange membrane acting as the electrolyte. They hold great promise for clean and efficient power generation. Enhancing performance and reducing costs remain central goals in the multidisciplinary field of PEMFC research. Key components include the anode, cathode, and proton exchange membrane, with ongoing efforts focused on improving electrode performance and developing more durable, cost-effective membrane materials. Our group specializes in both 2D materials and PEMFC research, and we are actively investigating how 2D materials can enhance the performance and durability of PEMFC systems. We welcome you to visit our 2D materials lab to explore potential collaborations aimed at advancing PEMFC technology and positioning it as a more competitive energy solution.

Multi-functional nanocoating

for energy and environmental applications

2D materials with structure control have various potential applications in the thin film industry, beyond just membrane technology. Their properties, including electrical conductivity, mechanical strength, light absorption, and thermal conductivity, can be customized by adjusting their atomic structure and composition. Carbon-based structured 2D materials, for instance, have high conductivity and can be utilized as energy storage electrodes in batteries and supercapacitors. They can also be used to produce high-value added thin films such as electromagnetic wave shields and heat-conducting films. On the other hand, semiconductor and inorganic porous 2D materials with insulating properties are suitable for applications like photo-reactive membrane reactors, low-k thin films, and drug delivery.

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