POM-Based Water Splitting Catalyst Under Acid Conditions Driven by Its Assembly on Carbon Nanotubes

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis
• Nanotechnology

Background:

• Development of efficient and stable bifunctional electrocatalysts for water electrolysis under acidic conditions is crucial for sustainable hydrogen production.
• Existing electrocatalysts often require expensive noble metals or lack stability and tunability for selective oxygen or hydrogen evolution.

Purpose of the Study:

• To develop a novel vanadium polyoxometalate (POM)-based material with switchable electrocatalytic activity for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER).
• To investigate the role of nanoassembly and non-innocent cations in tuning the bifunctional electrocatalytic performance for green hydrogen production.

Main Methods:

• Synthesis and characterization of a vanadium polyoxometalate material, Na₄(H₂O)₁₂(CH₂OH)₃CNH₃]₂[V₁₀O₂₈]·4H₂O (1).
• Assembly of the POM material on carbon nanotubes (CNT) via physical mixture (1/CNT) and directed assembly (1@CNT).
• Electrochemical evaluation of OER and HER performance using techniques including in-operando confocal microscopy and theoretical calculations.

Main Results:

• The physical mixture (1/CNT) exhibited remarkable OER activity (0.34 V overpotential at 10 mA cm⁻²) surpassing commercial IrO₂.
• The directed assembly (1@CNT) demonstrated high HER efficiency (onset potential of -0.07 V) comparable to Pt/C, with high Faradaic efficiencies for both reactions (80% for OER, 94% for HER).
• Mechanistic studies revealed that OER proceeds via alcohol oxidation, while HER is facilitated by TRIS⁺ moieties acting as a 'proton sponge', with modulation of crystal interactions and local microenvironment being key.

Conclusions:

• A novel POM-based material with switchable bifunctional electrocatalytic activity (OER/HER) was successfully developed through controlled nanoassembly on CNTs.
• The study highlights a rational design strategy for bifunctional molecular electrocatalysts using earth-abundant elements and controlled assembly for advanced green hydrogen production.
• This approach offers a promising pathway for developing efficient and stable electrocatalysts for sustainable energy applications.