Electrochemical Capacitance Traces with Interlayer Spacing in Two-dimensional Conductive Metal-Organic Frameworks

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Electrically conductive metal-organic frameworks (MOFs) are explored for electrochemical capacitors (ECs) due to high surface area and redox activity.
• Maximizing energy density in ECs involves both double-layer capacitance and faradaic processes, common in inorganic pseudocapacitors.
• Systematic studies on charge storage mechanisms and structure-property relationships in conductive MOFs are limited.

Purpose of the Study:

• Investigate charge storage mechanisms in triazatruxene-based 2D conductive MOFs.
• Understand how alkyl functionalization influences structural parameters and electrochemical performance.
• Establish structure-property relationships for optimizing energy storage in MOF-based ECs.

Main Methods:

• Synthesized a series of Ni3(HIR3-TAT)2 MOFs with varying alkyl groups (R=H, Et, n-Bu, n-Pent).
• Characterized MOF structures and systematically varied interlayer spacing via R-group functionalization.
• Analyzed charge storage mechanisms, distinguishing between double-layer capacitance and pseudocapacitance.

Main Results:

• Alkyl functionalization modulated interlayer spacing, shifting the charge storage mechanism.
• Capacitance increased from Ni3(HIH3-TAT)2 to Ni3(HIBu3-TAT)2 as the mechanism shifted towards pseudocapacitance.
• Partial exfoliation of Ni3(HIBu3-TAT)2 enhanced accessibility of redox-active sites, increasing faradaic contributions.

Conclusions:

• Tuning MOF structure, specifically interlayer spacing via functionalization, controls charge storage mechanisms.
• This strategy enhances molar specific capacitance and can be leveraged for designing advanced electrode materials for ECs.
• Understanding and controlling charge storage mechanisms in conductive MOFs is key for future energy storage applications.