Enhanced Proton Conduction via Proton-Coupled Electron Transfer Reaction by a Keplerate-Type Polyoxometalate Capsule

Area of Science:

• Materials Science
• Inorganic Chemistry
• Electrochemistry

Background:

• Polyoxometalates (POMs) are anionic metal-oxide clusters with diverse structures and selective element incorporation.
• Keplerate-type POMs, or POM capsules, possess core-shell architectures suitable for proton conduction.
• Existing POM capsules offer large surface areas but require functionalization to optimize proton transport.

Purpose of the Study:

• To introduce proton carriers into POM capsules via proton-coupled electron transfer (PCET).
• To investigate the impact of electron incorporation on proton conductivity.
• To enhance proton conduction efficiency in POM-based materials.

Main Methods:

• Synthesis of POM capsules with varying degrees of electron incorporation (0 to 11 electrons).
• Utilized proton-coupled electron transfer (PCET) for controlled functionalization.
• Measured and compared proton conductivity across different electron incorporation levels.

Main Results:

• POM capsules with 3 incorporated electrons demonstrated a tenfold increase in proton conductivity compared to pristine or highly reduced counterparts.
• Excessive reduction was found to hinder proton conduction due to increased electrostatic interactions.
• PCET effectively modulated proton conductivity without element-specific limitations.

Conclusions:

• Proton-coupled electron transfer is a viable strategy for enhancing proton conductivity in POM capsules.
• The core-shell structure of POM capsules, when combined with optimized PCET, significantly improves proton transport.
• This study provides a proof of concept for designing advanced proton-conductive materials using POMs.