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, singleatom Cu is bridged into C 3 N 4 sheet interlayers through the thermal condensation of selfassembly 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.

Accelerating photocatalytic hydrogen production by anchoring Pt single atoms on few-layer g-C3N4 nanosheets with Pt–N coordination

“…The significant increase in the surface area and pore volume of Pt 0.5 /g-C 3 N 4 can be attributed to the fact that the uniform dispersion of isolated Pt atoms can enlarge the interlayer distance of g-C 3 N 4 structures. 27,42,43 As the Pt content exceeds 0.5%, the specific surface area and pore volume exhibit a declining trend, but Pt x /g-C 3 N 4 still demonstrates the ability to offer an increased number of micropores as active sites for the photocatalytic reaction.…”

Order–Disorder Engineering of Carbon Nitride for Photocatalytic H2O2 Generation Coupled with Pollutant Removal

“…23 Thereinto, the terrible recombination of charge carriers should be taken into consideration, which motivates the structure modification for promoted photocatalytic performance. In this regard, diverse strategies have been utilized to address the drawbacks of g-C 3 N 4 during the past decades, including the control of crystallinity, 24 the construction of heterojunctions, 25 the loading of cocatalysts, 26 the doping of elements, 27 and the modulation of morphology. 28 Intriguingly, it has been verified that the synthesis of crystalline g-C 3 N 4 can avoid the formation of trapping centers or recombination sites, thus effectively suppressing charge recombination.…”

Strengthened H2O adsorption and photogenerated carrier separation: surface C-coupled hydroxylation of g-C3N4 photocatalysts for efficient H2 production

“…Due to the intrinsic properties of g-C 3 N 4 fabricated using melamine, dicyandiamide, and urea, 32,33 the occupancy of the hydroxyl group within the pristine g-C 3 N 4 structure is relatively limited. Up to now, several methods aimed at introducing hydroxyl groups to the g-C 3 N 4 surface, but it is difficult to ensure their stability in photocatalytic systems.…”

“…18,19,21,22 During photocatalysis, the unsaturated carbon is usually slightly attached to the methyl hydroxyl group (C–OH) in solution to gain activity. 32–34 Inspired by the combination of melamine and formaldehyde, 35 it is expected that the unsaturated carbon on g-C 3 N 4 could be integrated with the methyl–hydroxyl group (C–OH) in formaldehyde solutions.…”