An All‐Organic D‐A System for Visible‐Light‐Driven Overall Water Splitting

Abstract Direct water splitting over photocatalysts is a prospective strategy to convert solar energy into hydrogen energy. Nevertheless, because of the undesirable electron accumulation at the surface, the overall water‐splitting efficiency is seriously restricted by the poor charge separation/transfer ability. Here, an all‐organic donor–acceptor (D‐A) system through crafting carbon rings units‐conjugated tubular graphitic carbon nitride (C‐TCN) is proposed. Through a range of characterizations and theoretical calculations, the incorporation of carbon rings units via continuous π‐conjugated bond builds a D‐A system, which can drive intramolecular charge transfer to realize highly efficient charge separation. More importantly, the tubular structure and the incorporated carbon rings units cause a significant downshift of the valence band, of which the potential is beneficial to the activation for O 2 evolution. When serving as photocatalyst for overall water splitting, C‐TCN displays considerable performance with H 2 and O 2 production rates of 204.6 and 100.8 µmol g −1 h −1 , respectively. The corresponding external quantum efficiency reaches 2.6% at 405 nm, and still remains 1.7% at 420 nm. This work demonstrates that the all‐organic D‐A system conceptualized from organic solar cell can offer promotional effect for overall water splitting by addressing the charge accumulation problem rooted in the hydrogen evolution reaction.