Plasma-Induced Heptazine Distortion in Potassium Poly(heptazine imide) for Enhanced H₂O₂ Photosynthesis with Near-Infrared Response.

Abstract

Photosynthesis is a promising strategy for hydrogen peroxide (H₂O₂) production, but its photocatalytic efficiency is limited by insufficient charge separation and a narrow light response. Here, we adopt a plasma treatment strategy to distort the heptazine unit structure in potassium poly(heptazine imide) (K-PHI) from a planar to a corrugated shape. The distortion of the heptazine unit in K-PHI enhances the dipole moment and built-in electron field in favor of efficient charge separation. Structural distortion in K-PHI alters the symmetry of heptazine rings, allowing partial coplanarity between n and π electron clouds. This corrugated structure promotes <i>n</i> → π* electronic transition, extending the visible light absorption. Meanwhile, potassium-heavy doping extends the lifetime of the photogenerated electrons and effectively increases the near-infrared light absorption intensity. Consequently, the corrugated K-PHI (CK-PHI-5) exhibits production rates of 11.6 mmol g^-1 h^-1 for H₂O₂ and 11.5 mmol g^-1 h^-1 for benzaldehyde. CK-PHI-5 also achieves exceptional near-infrared light-driven H₂O₂ production performance with rates of 1061.7 μmol g^-1 h^-1 at 808 nm and 697.7 μmol g^-1 h^-1 at 940 nm. This study demonstrates the use of PHI for photocatalytic H₂O₂ production using near-infrared light and develops a fast and effective plasma treatment method to awaken the structural distortion of PHI.