Terminal groups enable tunable versatile MXene materials
A review in Nano Research highlights how terminal groups (Tₓ) on MXenes influence their properties and applications, emphasizing their potential for tailored electronic, optical, and mechanical functionalities.
MXenes, which are atomically thin transition metal carbides and nitrides, are gaining renewed attention due to their unique surface properties. During production, the 'A' layers of MAX-phase precursors are selectively etched, leaving Mₙ₊₁Xₙ sheets with exposed transition-metal sites. These sites quickly react with the environment, forming terminal groups, denoted as Tₓ, by binding with heteroatoms such as oxygen, fluorine, and chlorine. These terminal groups play a crucial role in tuning the material's properties.
The challenge lies in the uncertainty of Tₓ. According to Prof. Peng-an Zong of Nanjing Tech University, tailoring these terminal groups is essential for making MXenes suitable for specific applications. For example, different terminal chemistries in Nb₂CTₓ MXene can lead to varied functionalities. Tₓ = −S or −Se is linked to thermoelectric potential, while Tₓ = −Cl is associated with superconductivity. When terminals are primarily −OH, Nb₂CTₓ can be used as an anode plate in aqueous energy storage.
A new review in Nano Research positions surface chemistry as the key 'design knob' for MXenes. The review, titled 'Terminal Groups: The Key to Tunable and Versatile MXenes Materials,' discusses structural features and modification strategies for Tₓ. It connects terminal-group chemistry to changes in electrical, optical, magnetic, and mechanical properties, and explores applications in sensing, filtration membranes, and catalysis.
The authors highlight that terminal groups reshape electronic landscapes, though the field lacks universal principles. Zong notes that relying solely on calculated band structures and density of states can be superficial, as band modulation by Tₓ is complex. The review also addresses a theoretical challenge: establishing criteria for identifying MXenes that are both high-energy and stable with multifunctional surfaces.
The review argues that MXenes' distinct advantage is the tunability of Tₓ. If terminal groups can be precisely engineered, MXenes could evolve from a laboratory curiosity to a versatile material platform tailored for specific device environments. The review was published on March 17, 2026, supported by Jiangsu PAPD and the Jiangsu Collaborative Innovation Center for Advanced Inorganic Function Composites.
Source: MXenes