Engineering Surface N‐Vacancy Defects of Ultrathin Mesoporous Carbon Nitride Nanosheets as Efficient Visible‐Light‐Driven Photocatalysts

Abstract

Graphitic carbon nitride (GCN) has become an attractive photocatalyst for solar energy conversion, but the photocatalytic activity of GCN is still limited by the extremely fast electron–hole recombination. Herein, a defective ultrathin mesoporous graphitic carbon nitride (DUMCN) photocatalyst with high specific surface area and mesoporous structure is fabricated through a facile three‐step heat‐treatment strategy, which reduces the distance of bulk photogenerated carriers to the surface, resulting in efficient adsorption and diffusion of reactants and products, and exposing adequate surface active sites. Moreover, suitable N‐vacancy defects are formed via high‐temperature surface hydrogenation, which can extend light absorption and produce ultra‐high intrinsic carrier mobility, and further increase the active sites. The photocatalytic hydrogen production rate is up to 13.63 mmol h−1 g−1 under visible light in the triethanolamine solution and 33.5 μmol h−1 g−1 for overall water splitting, which is much higher than that of bulk graphitic carbon nitride (BCN) structures. Density functional theory (DFT) calculations further reveal the effect of surface defects on the band structure for promoting the spatial charge separation. This facile strategy may offer new insights into designing other ultrathin mesoporous semiconductor photocatalysts with high performance.

S‐Scheme Photocatalytic Systems

“…[21,22] Moreover, H 2 O adsorption and activation on surface active sites of photocatalysts are also important for STH process. [23][24][25][26][27] In S-scheme photocatalytic system, Fermi energy level difference ensures that the so-generated built-in electric field promotes the efficient separation and migration of photogenerated electrons and holes through the curved and matched energy bands. The spontaneous electron migration induced by Fermi energy difference can activate the surface of photocatalytic materials, provide the adsorption and activation of H 2 O molecules, and decrease the reduction overpotential of H 2 O.…”

Heteroatom-induced domain electrostatic potential difference in ZnIn2S4nanosheets for efficient charge separation and boosted photocatalytic overall water splitting

“…3f exhibits the N 2 adsorption–desorption isotherms of the ZIS and Al-ZIS nanosheets, and both samples show typical type-IV isotherms according to the IUPAC classification and a hysteresis loop at a relative pressure ( p / p 0 ) from 0.4 to 1.0, indicating that there are numerous mesoporous structures in the ZIS and Al-ZIS nanosheets. 33–35 Based on isotherms, Brunauer–Emmett–Teller (BET) surface areas and pore volumes were further obtained. As shown in Fig.…”

In situ synthesis of holey g-C3N4 nanosheets decorated by hydroxyapatite nanospheres as efficient visible light photocatalyst

“…It can be seen that HAp/g-C 3 N 4 illustrated a higher amount of OHc radical in comparison with HAp and g-C 3 N 4 . 25,26 ESR analysis also conrmed the production of more OHc radicals by HAp/g-C 3 N 4 . Other works have also shown that the g-C 3 N 4 nanocomposite produced more oxygen radicals under light irradiation in comparison to single g-C 3 N 4 .…”

“…23 An effective photocatalyst of oxygen edged holey g-C 3 N 4 nanosheets was constructed under photo-Fenton-reaction and UV irradiation with remarkable pollutant degradation. 24,25 Moreover, porous holey nanosheets were synthesized via the pre-polymerization method showing high photocatalytic H 2 evolution under ammonia gas pressure. 26 Also, similar works for the preparation of the mentioned morphologies suffer from complex processes and are timeconsuming.…”