In-Plane and Out-of-Plane Polarities Synergistically Boost Photocatalytic Overall Water Splitting on Two-Dimensional...

Area of Science:

• Materials Science
• Photocatalysis
• Nanotechnology

Background:

• Covalent organic frameworks (COFs) show promise for overall photocatalytic water splitting (OWS).
• Their performance is limited by insufficient driving force and rapid recombination of photogenerated carriers.
• Existing COF designs often lack strategies to overcome these limitations.

Purpose of the Study:

• To propose and theoretically investigate 2D COFs with dual in-plane/out-of-plane polarities for enhanced OWS.
• To elucidate the mechanism by which dual polarities improve charge separation and catalytic efficiency.
• To provide theoretical guidance for designing high-performance COF photocatalysts.

Main Methods:

• First-principles calculations to determine electronic structures and band alignments.
• Nonadiabatic molecular dynamics (NAMD) simulations to analyze carrier dynamics.
• Theoretical modeling of TTA-BTPA and TAPB-BTPA COF bilayers and monolayers.

Main Results:

• Dual in-plane and out-of-plane polarities in 2D COF bilayers create a dual type-II band alignment.
• This alignment promotes efficient intra- and inter-layer charge separation, suppressing carrier recombination.
• Calculated carrier lifetime for TTA-BTPA bilayer is 6.61 times longer than its monolayer.
• Built-in electric field enhances the driving force for water splitting.
• Simulated bilayers show excellent visible-light absorption and potential for >10% solar-to-hydrogen efficiency.

Conclusions:

• Dual polarity is an effective strategy to enhance COF performance for overall photocatalytic water splitting.
• The synergistic effect of dual polarities significantly improves charge carrier dynamics and catalytic driving force.
• This research provides a theoretical framework for developing advanced 2D COF materials for efficient solar fuel production.