Bimodal activated carbons derived from resorcinol-formaldehyde cryogels

Area of Science:

• Materials Science
• Porous Materials
• Carbon Materials

Background:

• Resorcinol-formaldehyde (RF) cryogels are precursors for carbon materials.
• Pyrolysis and acid activation are common methods for carbon material synthesis.
• Understanding pore structure development is crucial for optimizing carbon properties.

Purpose of the Study:

• To investigate the pore texture of RF cryogels activated with phosphoric acid.
• To compare these materials with those obtained by pyrolysis.
• To optimize the acid activation process for high-surface-area microporous carbons.

Main Methods:

• RF cryogels were prepared at various dilution ratios.
• Cryogels were activated using phosphoric acid (H3PO4) at 450 °C.
• Control samples were pyrolyzed at 900 °C for comparison.

Main Results:

• Acid-activated cryogels exhibited different pore textures compared to pyrolyzed samples.
• Highly diluted cryogels yielded microporous carbons with high surface areas.
• Optimized activation (2 M H3PO4, optimal contact time) achieved surface areas up to ~2200 m² g⁻¹ and micropore volumes of ~0.7 cm³ g⁻¹.
• Activation at 1.2 M H3PO4 produced bimodal carbons with accessible macroporosity.

Conclusions:

• Phosphoric acid activation of RF cryogels is an effective route to high-surface-area microporous carbons.
• Dilution ratio, acid concentration, and contact time are critical parameters for controlling pore structure.
• Optimized activation offers a viable alternative to pyrolysis for producing advanced carbon materials.