Interfacial Charge Transfer Activates Graphene Shells for High-Efficiency and Durable Vanadium-Cerium Redox Flow...

Area of Science:

• Energy Storage
• Materials Science
• Electrochemistry

Background:

• Vanadium-cerium redox flow batteries (V-Ce RFBs) offer higher voltage and lower cost than vanadium-only systems.
• Sluggish cerium redox kinetics and poor stability in acidic conditions limit V-Ce RFB practical use.
• Existing strategies provide limited improvements in V-Ce RFB performance and durability.

Purpose of the Study:

• To develop a novel, high-performance electrocatalyst for V-Ce RFBs.
• To address the kinetic limitations of the Ce3+/Ce4+ redox reaction.
• To enhance the stability and efficiency of V-Ce RFBs under acidic conditions.

Main Methods:

• Synthesis of iron-cobalt alloy nanoparticles encapsulated in a graphene shell (FeCo@Gr).
• Electrochemical characterization of FeCo@Gr as a positive electrode material for V-Ce RFBs.
• Single-cell battery testing to evaluate performance metrics like energy efficiency and power density.
• Density functional theory (DFT) calculations to understand reaction mechanisms.

Main Results:

• The FeCo@Gr electrocatalyst significantly improved catalytic activity for the Ce3+/Ce4+ redox reaction compared to pristine graphene.
• Single-cell tests demonstrated a 63.4% energy efficiency at 200 mA cm-2 and a peak power density of 433 mW cm-2.
• The graphene shell provided corrosion resistance and facilitated charge transfer, lowering the reaction energy barrier.
• DFT calculations confirmed the beneficial electronic coupling between the alloy core and graphene shell.

Conclusions:

• FeCo@Gr is a highly effective electrocatalyst for V-Ce RFBs, overcoming kinetic limitations.
• The developed catalyst offers enhanced durability and significantly improved battery performance.
• This strategy presents a viable route for creating advanced electrocatalysts for next-generation flow batteries.