Redox Self-Equilibration in Molecular Vanadium Oxide Mixtures Enables Multi-Electron Storage

Area of Science:

• Materials Science
• Electrochemistry
• Inorganic Chemistry

Background:

• Polyoxometalates (POMs) are crucial for multi-electron storage in energy technologies.
• Current applications utilize single POM species, limiting storage capacity within a specific potential window.

Purpose of the Study:

• To develop POM systems with enhanced redox reactivity and multi-electron storage capabilities.
• To explore the formation and properties of mixed polyoxovanadate co-crystals.

Main Methods:

• Non-aqueous self-assembly of a vanadate precursor in the presence of Mg2+.
• Synthesis of mixed-valent (VIV/V) species: {MgV13} and {V14}.
• Co-crystallization of {MgV13} and {V14} in a 1:1 molar ratio.
• Electrochemical studies in solution to determine redox transitions.

Main Results:

• Formation of two related polyoxovanadates, {MgV13} (3-electron reduction) and {V14} (5-electron reduction).
• Co-crystallization of these species leading to significantly increased redox reactivity.
• Observation of up to fourteen reversible redox transitions in the potential range of -2.15 V to +1.35 V (vs Fc+/Fc).

Conclusions:

• Redox self-equilibration during synthesis provides access to well-defined molecular mixtures of mixed-valent metal oxides.
• This approach opens new avenues for designing advanced molecular energy storage materials.
• The synthesized mixed POM system demonstrates superior multi-electron storage potential.