Electrocatalytic Water Splitting in Isoindigo-Based Covalent Organic Frameworks

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Developing efficient electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is crucial for energy storage and conversion.
• Current challenges include achieving low cost, robustness, and high performance under both acidic and basic conditions.

Purpose of the Study:

• To synthesize and characterize novel imine-linked isoindigo-based covalent organic networks (CONs).
• To investigate the effect of core amine unit planarity on material morphology and electrocatalytic activity.
• To evaluate the performance of synthesized materials as electrocatalysts for OER and HER.

Main Methods:

• Synthesis of two CONs, I-TTA (planar triazine core) and I-TG (non-planar guanidinium core), via imine linkage.
• Characterization of material morphology, crystallinity, and electrochemical properties.
• Electrocatalytic testing for HER and OER in acidic and basic electrolytes, respectively.

Main Results:

• I-TTA formed a 2D nanosheet covalent organic framework (COF) with high crystallinity, while I-TG formed an amorphous covalent organic polymer (COP) with fibrous morphology.
• I-TTA exhibited superior electrocatalytic activity for both HER (134 mV overpotential for 10 mA cm⁻² current density in H₂SO₄) and OER (283 mV overpotential in KOH).
• I-TTA demonstrated OER activity surpassing other metal-free COFs and maintained stability over 24 hours and 500 cycles.

Conclusions:

• The planarity of the core amine unit significantly influences the structure and electrocatalytic performance of isoindigo-based CONs.
• The crystalline, planar I-TTA COF is a promising metal-free electrocatalyst for efficient and stable OER and HER.
• This work offers a new strategy for designing high-performance electrocatalysts for renewable energy technologies.