Rational design of a carbon nitride photocatalyst with in-plane electron delocalization for photocatalytic hydrogen evolution†

Photocatalytic hydrogen evolution based on the use of carbon nitride (CN) catalyst offers a sustainable route to convert solar energy into hydrogen energy; however, its activity is severely restricted by the sluggish transfer of photogenerated charges. Herein, we report a novel approach involving boron (B) doping-induced π-electron delocalization in CN for efficient hydrogen (H₂) evolution. The as-prepared B-doped CN (BCN) catalyst presented an 8.6-fold enhancement in the H₂-evolution rate (7924.0 μmol h⁻¹ g⁻¹) under visible-light irradiation compared with pristine CN, which corresponded to an apparent quantum yield (AQY) of 14.5% at 405 nm. Experimental analysis and density functional theory (DFT) calculations demonstrated that B doping induced π-electron delocalization in conjugated CN rings to generate a new intermediate state within the band gap to provide a new transfer path for visible-light utilization, thus achieving the high separation and transfer of photoinduced carriers. This work provides a new approach to adjust the electronic structure of CN-like conjugated polymer semiconductors for efficient catalytic energy conversion.

Keywords: B doping; π-electron delocalization; H₂ evolution; Photocatalysis.