New opportunities for electrochemical applications

May 22, 2023

(Nanowerk News) Metal-organic frameworks (MOFs) are materials that have received significant attention in the energy field due to their unique characteristics, such as high specific surface area, extraordinary porous structure and excellent adaptability. However, they are constrained by their low electrical conductivity and chemical instability, which pose a barrier to their wide-scale use.

Enter MXene, a new material with abundant surface area and high conductivity. This has been proposed as a potential solution to improve the stability and conductivity of basic MOFs. The resulting MXene/MOF hybrid has better conductivity, more complex surface chemistry, and a stepped structure that allows for faster movement of electrons and ions, resulting in better electrochemical properties. This hybrid is even more impressive because it can be customized into various forms, each with a unique design and even better electrochemical performance.

For this reason, the careful fabrication of these MXene/MOF hybrids and their derivatives for use in energy-related devices is an area of ​​great interest. To encourage more research into these composites, scientists in China have reviewed the current state of research in this area and provided potential avenues for future exploration.

They publish their work on Material Energy Advances (“Metal–Organic Framework Meets MXene: New Opportunities for Electrochemical Applications”). Illustration of the characteristics of the MOF, MXene, and MXene/MOF composites and their derivatives. (Image: Hui Yang, School of Chemistry and Chemical Engineering, Yangzhou University)

Huan Pang, professor at the School of Chemistry and Chemical Engineering, Yangzhou University, and author of the recent paper, emphasized the importance of exploring MXene/MOF hybrid materials for their high electrochemical performance potential. “The relevance of MXene/MOF hybrids in energy-based applications has increased significantly in recent years,” he said.

Professor Pang explained the reasons why the MXene/MOF hybrid material was designed. First of all, MXene has an abundant negative surface charge which makes it a suitable substrate for MOF growth. This not only prevents agglomeration of the MOF particles and MXene sheets but also provides more available surface area. Second, the MXene structure in this hybrid is highly conductive, offering an efficient conductive pathway and minimizing ion diffusion distances. Third, the strong bond between MXene and MOF ensures excellent structural stability. Lastly, the adaptable structure and various forms of the MOF can help these hybrids meet different specific applications. Thus, using MXene/MOF hybrids in high-performance electrochemical devices looks promising.

In his paper, Pang provides a complete description of the method for preparing MXene/MOF composites and the steps for producing MXene/MOF derived materials. He also extensively examines and summarizes the critical electrochemical applications of these composites and their derivatives. These include use in supercapacitors, various types of batteries, water splitting, and oxygen reduction reactions. “By introducing MXene, we were able to counteract the chemical instability and poor electrical conductivity of MOFs. On the other hand, MOF can overcome the problem of severe oxidation degradation and self-depositing of MXene,” explains Pang. He added that MXene/MOF composites have been found to outperform pure MXene and native MOF in electrochemical properties, due to their well-planned structure, strong bonds, multiple active sites, and broad conductive pathways.

Despite much progress in MXene/MOF composites and their derivatives, Pang points out that their application in electrochemistry is still new. He went on to discuss the main challenges and prospects for this composite. “It is essential to increase the variety of MXene/MOF hybrids, improve their synthesis methods, establish interfacial interactions, design complex structures, investigate MXene-derived MOFs, fabricate energy-linked devices, and understand their mechanism of action,” explained Pang.

Although hurdles have not been overcome for MXene/MOF composites and their derivatives, Pang notes their substantial contribution to electrochemical energy storage and conversion. “The review should foster a deeper understanding of functional MXene/MOF composites and pave the way for their future development in electrochemical applications,” Pang concluded.

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