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 (C3N4) 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 C3N4 is severely limited by its poor photoinduced electron/hole pair separation and interlayer charge transport. Herein, single-atom Cu is bridged into C3N4 sheet interlayers through the thermal condensation of self-assembly supramolecules of Cu precursors and melamine–cyanuric acid monomers. Simultaneously, N vacancies are engineered into C3N4 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 C3N4, allowing more electrons to pass through the delocalized π-conjugated network of C3N4 to Cu sites, which facilitates charge transfer between C3N4 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.