Single-Atom Cu Channel and N-Vacancy Engineering Enables Efficient Charge Separation and Transfer between C₃N₄ Interlayers for Boosting Photocatalytic Hydrogen Production

Abstract

Polymeric carbon nitride (C 3 N 4 ) has attracted great attention in photocatalysis due to its low-cost, visible-light response, and environment-friendly merits. However, the catalytic efficiency of pristine bulk C 3 N 4 is severely limited by its poor photoinduced electron/hole pair separation and interlayer charge transport. Herein, single-atom Cu is bridged into C 3 N 4 sheet interlayers through the thermal condensation of self-assembly supramolecules of Cu precursors and melamine–cyanuric acid monomers. Simultaneously, N vacancies are engineered into C 3 N 4 only by gradient temperature. The single-atom Cu bridges serve as electron channels to promote photoinduced electron/hole pair separation and interlayer charge transport. The experimental results and calculations demonstrate that N vacancies break the symmetry of pristine C 3 N 4, allowing more electrons to pass through the delocalized π-conjugated network of C 3 N 4 to Cu sites, which facilitates charge transfer between C 3 N 4 layers, resulting in more effective separation of electron/hole pairs, optimal charge distribution, and lower hydrogen evolution barrier. As a result, the photocatalyst at a stationary point with a 1 wt % Pt cocatalyst presents a high visible-light photocatalytic hydrogen production rate (11.23 mmol g –1 h –1 ), reaching a high apparent quantum yield of 31.60% at 420 nm. It is noted that the photocatalyst still exhibits a high hydrogen production rate of 605.15 μmol g –1 h –1 in the absence of the Pt cocatalyst.