Achieving enhanced ionic mobility in nanoporous silica by controlled surface interactions.

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Emerging gels utilize nanoporous silica micro-particles for ionic mobility applications.
• Ionic liquids confined within nanoporous materials are key for energy storage and conversion.
• Understanding and enhancing ionic mobility in these systems is critical for device performance.

Purpose of the Study:

• To investigate a strategy for enhancing ionic mobility in silica-based gels via chemical surface functionalization.
• To explore the impact of surface interactions on ionic liquid behavior within nanoporous silica.
• To evaluate the potential of these functionalized gels as solid-like electrolytes for energy devices.

Main Methods:

• Chemical functionalization of robust nanoporous silica micro-particle surfaces.
• Filling silica nano-pores with two distinct ionic liquids: aprotic (C6C1ImTFSI) and protic (DEMAOMs).
• Characterization using solid-state NMR, diffusion NMR, and dielectric spectroscopy across a temperature range of -10 to 140 °C.

Main Results:

• Chemical functionalization significantly enhances ionic mobility of both ionic liquids within silica nano-pores compared to untreated silica.
• The enhancement is more pronounced at lower pore filling factors and across the entire temperature range studied.
• NMR and dielectric spectroscopy confirm weaker intermolecular interactions and a flipped-ion effect at the functionalized silica interface.

Conclusions:

• Controlling surface interactions through chemical functionalization is an effective strategy to boost ionic mobility in silica-based gels.
• These structurally tunable gels exhibit promising properties as solid-like electrolytes.
• The findings are highly relevant for the development of advanced energy storage and conversion devices, including Li-ion batteries and proton exchange membrane fuel cells.