Electrocatalytic Performance of M₅X₄ MXenes for Hydrogen Evolution Reaction

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• M5X4 MXenes are a subclass of 2D transition metal carbides, notable for their thickness.
• Previous research indicated promising electrocatalytic activity but lacked detailed analysis of composition and interlayer spacing effects on hydrogen evolution reaction (HER).

Purpose of the Study:

• To systematically investigate the impact of metal composition and interlayer spacing on the HER activity of M5X4 MXenes.
• To explore the potential of TMA+-intercalated Mo4VC4 for sustainable hydrogen production.

Main Methods:

• Synthesis and characterization of three M5X4 MXenes: Mo4VC4, (TiTa)5C4, and (TiNb)5C4.
• Modulation of interlayer spacing and composition via ion exchange using tetramethyl ammonium (TMA+) and lithium (Li+).
• Electrochemical evaluation of HER performance, including areal and gravimetric overpotentials.

Main Results:

• TMA+-intercalated Mo4VC4 demonstrated superior HER activity with overpotentials of 172 mV (areal) and 90 mV (gravimetric).
• Li+-exchanged Mo4VC4 showed increased overpotentials (212 mV areal, 131 mV gravimetric) due to reduced interlayer spacing.
• (TiNb)5C4 and (TiTa)5C4 exhibited higher overpotentials, suggesting suitability for supercapacitors or aqueous batteries.

Conclusions:

• Interlayer spacing and metal composition critically influence HER activity in M5X4 MXenes.
• TMA+-Mo4VC4 is identified as a highly promising material for efficient and sustainable hydrogen generation.
• Other M5X4 MXenes show potential for energy storage applications.