The Collision between g‐C₃N₄ and QDs in the Fields of Energy and Environment: Synergistic Effects for Efficient Photocatalysis

Abstract

Among all possible options, semiconductor photocatalytic technology is considered as an environmentally friendly and ideal strategy among all possible options and has been rapidly developed around the world. [5][6][7][8][9] Since the first report of artificial photocatalysis in 1972 by Fujishima et al., traditional TiO 2 has been widely used because of its intrinsic photocatalytic performance, low toxicity, and thermodynamic stability. [10][11][12] However, TiO 2 can be only photogenerated under ultraviolet light (UV-light), limiting its utilization efficiency of solar energy. [13,14] Accordingly, researchers are actively searching for photocatalysts with excellent visible light response and satisfactory photocatalytic performance. [15][16][17] Graphitic carbon nitride (g-C 3 N 4 ) is a metal-free nanomaterial composing of C and N with a defect-N bridges of s-triazine or tri-s-triazine (Figure 1A,B). [19,20] The history of C 3 N 4 could be traced back to 1834, but g-C 3 N 4 was not formally proposed until 1996 by Teter and Hemley, probably due to its high stability and mysterious structure. [21] Subsequently, g-C 3 N 4 has emerged as an encouraging candidate for photocatalysts based on its moderate bandgap, suitable energy band structure (Figure 1C), visible light absorption and high stability, as well as been widely concerned by countries all over the world. [18,[22][23][24] Since the photocatalytic H 2 evolution of g-C 3 N 4 was first reported in 2009, the research on improving the photocatalytic performance of g-C 3 N 4 -based photocatalysts has gradually become a popular research direction (Figure 2). [18,25,26] Pristine g-C 3 N 4 can be prepared by using the heat treatment of some low-cost nitrogen-rich organic precursors, such as urea, melamine, dicyandiamide, and so on. [27] However, their practical applications have been limited by several shortcomings of pristine g-C 3 N 4 , including low specific surface area, insufficient utilization of visible light (< 460 nm), and rapid recombination of photogenerated electron-hole (e − -h + ) pairs. [28,29] For the sake of overcoming these challenges, many methods have been employed to modify g-C 3 N 4 to improve the photocatalytic activity, such as element/heteroatomic doping, [30] structural design, [31,32] and heterojunction construction. [33][34][35] Among the recent progresses of modifying g-C 3 N 4 , heterojunctions formed Recently, graphitic carbon nitride (g-C 3 N 4 ) has attracted increasing interest due to its visible light absorption, suitable energy band structure, and excellent stability. However, low specific surface area, finite visible light response range (<460 nm), and rapid photogenerated electron-hole (e − -h + ) pairs recombination of the pristine g-C 3 N 4 limit its practical applications. The small size of quantum dots (QDs) endows the properties of abundant active sites, wide absorption spectrum, and adjustable bandgap, but inevitable aggregation. Studies have confirmed that the integration of g-C 3 N 4 and QDs not only overcomes these limita...

Transition Metal Chalcogenides Quantum Dots: Emerging Building Blocks toward Solar-to-Hydrogen Conversion

“…In the quantum world, however, quantum tunneling is a possible route to realize the electron transport between QDs and other semiconductors. (5) QDs own the shorter distance for the photogenerated e − and h + to quickly migrate to the surface active sites as compared to those with bigger particles, 46 thus lowering the recombination probability before water splitting. 47 Although charge separation is a problem when the charges are confined to a particle that has nm 3 volume, charge separation modulation actually represents a very pivotal sector for boosting the photoactivities of TMCs-based photocatalytic system since electrons and holes can thus participate in the photoreduction and photo-oxidation reactions, respectively.…”

Degradation of organic contaminants by peroxymonosulfate activated with zeolitic imidazolate framework-based catalysts: performances, mechanisms and stability

“…Various technologies have been developed to solve the problems of water pollution, including adsorption, 5 photocatalytic degradation, [6][7][8][9][10] biological treatment, 11 enzymatic degradation 12,13 and advanced oxidation processes (AOPs). [14][15][16][17][18][19] Among them, AOPs are effective means to oxidize macromolecular organic contaminants into harmless or lowtoxicity mineralized products by generating highly reactive oxygen species (ROS), such as sulfate (SO 4 ˙−) and hydroxyl (˙OH) radicals.…”

Construction of a heterojunction with fast charge transport channels for photocatalytic hydrogen evolutionviaa synergistic strategy of Co-doping and crystal plane modulation

“…In recent years, graphite phase carbon nitride (g-C 3 N 4 ), as a green solar energy conversion catalyst, has received continuous attention in the fields of carbon monoxide oxidation, N 2 photofixation in the near-infrared region and bacterial photocatalytic inactivation. [1][2][3] g-C 3 N 4 has unquestionable advantages such as non-toxicity, low cost, high stability, easy availability, and excellent electronic properties. However, effective charge separation and transfer remain decisive factors for photocatalytic hydrogen evolution activity.…”