MXenes with ordered triatomic-layer borate polyanion terminations

Area of Science:

• Materials Science
• Nanotechnology
• Surface Chemistry

Background:

• MXene properties are critically dependent on surface terminations, which have historically been limited to simple structures with poor stability.
• Existing MXene terminations often exhibit disordered arrangements, hindering optimal charge transport and device performance.

Purpose of the Study:

• To synthesize MXenes with novel triatomic-layer borate polyanion terminations (OBO terminations).
• To investigate the impact of these new terminations on the electronic properties and charge transport mechanisms of MXenes.
• To evaluate the potential of OBO-terminated MXenes for energy storage applications.

Main Methods:

• Employed a flux-assisted eutectic molten etching approach for MXene synthesis.
• Utilized Lewis acidic salts as etching agents and borax to generate BO₂^- species for surface capping.
• Characterized the electronic properties of OBO-terminated Nb₂C using d.c. conductivity and charge mobility measurements, analyzing transport via the Drude model.

Main Results:

• Successfully synthesized MXenes with ordered OBO terminations, contrasting with disordered conventional terminations.
• OBO-terminated Nb₂C exhibited a 15-fold increase in electrical conductivity and a 10-fold improvement in charge mobility compared to Cl/O-terminated Nb₂C.
• OBO-terminated Ti₃C₂ MXene demonstrated a high charge-storage capacity of 420 mAh g^-1 due to enriched Li⁺-hosting sites.

Conclusions:

• Intricate OBO terminations offer superior surface ordering, mitigating charge carrier scattering and enhancing electronic properties.
• The developed OBO-terminated MXenes show significant potential for advanced (opto)electronic devices.
• These novel MXenes present a promising platform for high-performance energy storage solutions.