Supercritical CO₂‐Tailored 2D Oxygen‐doped Amorphous Carbon Nitride for Enhanced Photocatalytic Activity

Abstract

Photocatalysis is considered as one of the most attractive strategies to make full use of sustainable solar light for chemical energy production and pollutant degradation. [1] Abundant active sites, sufficient light absorption ability, and rapid charge separation are the prerequisites for highly efficient photocatalysts. [2][3][4][5][6] Graphitic carbon nitride (g-C 3 N 4 ), as the analogue of graphene, has drawn broad attention on account of its unique optical and electronic properties, good chemical, and thermal stability. However, the over-stacking structure of the bulk g-C 3 N 4 leads to limited active sites and high charge recombination, as well as the insufficient visible-light absorption (bandgap %2.7 eV) severely restrict the photocatalytic performance of the bulk g-C 3 N 4 . [7,8] Two-dimensional (2D) amorphous nanosheets possess exceptional chemical, physical, and electronic properties because they integrate the benefits of both amorphous structure and 2D nature, such as large surface areas, abundant reactive sites, active electronic state, and additional ions/electrons transport paths. [9][10][11][12] 2D ultrathin or amorphous g-C 3 N 4 has been reported to possess superior catalytic activity than the bulk or crystalline counterparts. [13][14][15] However, the long-range disorder in the 2D amorphous nanosheets might suffer from inefficient charge transfer. [16] Heteroatom doping into the g-C 3 N 4 can change the carrier density and provide new electron transport pathways to promote charge separation and transport. [17][18][19][20][21] As one electron-rich atom with similar atom radius to that of nitrogen (N) atom, oxygen (O) atom is considered as an efficient dopant to be able to improve carrier separation and enlarge optical absorption ability. [20][21][22] To date, nevertheless, very few work have concentrated on studying the synergistic effect of the 2D amorphous structure and O-doping on the properties of the g-C 3 N 4 . [23] Therefore, the exploration of a facile and efficient approach to simultaneously achieve the O-doping on 2D amorphous g-C 3 N 4 , and precisely tailor the surface, crystallographic and electronic structure of the g-C 3 N 4 is desirable yet challenging.Supercritical CO 2 (SC CO 2 ), possessing both gas and liquid properties, that is low viscosity, high diffusion, low surface tension, and adjustable solvent characteristics, displays promising talent in 2D nanomaterials design and manufacture. [24,25] In our previous work, SC CO 2 can not only successfully exfoliate various layered materials into 2D nanosheets, [26,27] also achieve phase transformation, [28] heteroatom doping, [29] lateral and vertical heterostructure construction, [30][31][32][33] as well as 2D amorphous materials fabrication. [34][35][36] In this context, 2D O-doped amorphous g-C 3 N 4 nanosheets tailored by SC CO 2 have been first achieved in this work. Impressively, the introduction of SC CO 2 not only led to 2D amorphous structure but also created heteroatom O-doping in the C 3 N 4 skeleton, which caused intr...

Recycling Spent LiCoO2 Battery as a High‐efficient Lithium‐doped Graphitic Carbon Nitride/Co3O4 Composite Photocatalyst and Its Synergistic Photocatalytic Mechanism

“…It has been attracted much attention for pollutant degradation and H 2 production. [20][21][22] Unfortunately, the practical applications of g-C 3 N 4 face a challenge because of its low specific surface area, poor solar light utilization efficiency, and high recombination rate of photo-generated electron and hole. It is still needed to further improve the photocatalytic activity.…”

Recent advances in the fabrication of 2D metal oxides

“…This strain contributed to the formation of many atomic defects in the 3D V-O bonding network, and the unstable defective network then collapsed to 2D nanosheets. Additionally, 2D oxygen-doped amorphous carbon nitride materials were prepared with the assistance of SC-CO 2 , showing excellent photocatalytic activity due to increased surface area and abundant activity ( Du et al., 2021 ). The SC-CO 2 -assisted method provides a reference for the preparation of 2D amorphous MOXs, especially non-layered materials, from a limited source of precursors.…”

Tailor‐Engineered 2D Cocatalysts: Harnessing Electron–Hole Redox Center of 2D g‐C3N4 Photocatalysts toward Solar‐to‐Chemical Conversion and Environmental Purification

“…The resultant hybrid exhibited fast electron transfer rate due to minimized Schottky barrier and intimate contact of 2D/2D interfaces. [ 242 ] Besides that, this study also mentioned that oxygenated g‐C 3 N 4 possessed a suitable band structure for visible light absorption as well as exhibited large specific area, [ 245 ] which allowed the robust anchoring of 2D cocatalyst on its surface.…”