Polymeric Carbon Nitride‐Derived Photocatalysts for Water Splitting and Nitrogen Fixation

Abstract

Photocatalysis is a promising energy conversion and environmental restoration technology. The main focus of photocatalysis is the development and manufacture of highly efficient photocatalysts. Semiconductor‐based photocatalysis technology based on harnessing solar energy is considered as an attractive approach to solve the problems of global energy shortage and environmental pollution. Since 2009 pioneering work has been carried out on polymeric carbon nitride (PCN) for visible photocatalytic water splitting, thus PCN‐based photocatalysis has become a hot research topic, demanding significant research attention. This article reviews the physical and chemical properties, synthesis methods, and the methods to control the morphology, heteroatom doping, and construction of heterojunctions to improve the performance of PCN‐based photocatalysts in water splitting and nitrogen fixation. Through different design strategies, the photo‐generated electron‐hole pair separation efficiency of PCN materials can be effectively improved, thereby improving their photocatalytic performance. Finally, the challenges of PCN‐based photocatalysts in water splitting and nitrogen fixation applications are discussed herein. It is strongly believed that through different design strategies, efficient PCN‐based photocatalysts can be constructed for both water splitting and nitrogen reduction. These excellent modification strategies can be used as a guiding theory for photocatalytic reactions of other promising catalysts and further promote the development of photocatalysis.

Coupling photocatalytic water oxidation with organic reduction: strategy for using water to reduce organic molecules

“…In conclusion, we report, for the first time, that water is used as the electron donor to enable the reductive transformations of organic substances by coupling the light-induced water oxidation half-reaction with the reduction of organic compounds in the presence of Pd/g-C 3 N 4 * photocatalyst, which is different from previous literatures [44][45][46][57][58][59][60][61][62][63][64][65] related to light--driven water splitting where the proton reduction half-reaction is desired to occur, while this half-reaction would inhibit our reactions. The used photocatalyst was synthetized by a novel method where previous Pd/g-C 3 N 4 was irradiated by the light in the presence of Na 2 CO 3 and H 2 O.…”

“…In addition, the reductive coupling of aryl or alkyl halides is of great significance in modern organic synthesis [47][48][49][50][51][52][53][54][55][56] , which has prompted us to select this kind of reaction as the model reaction to make our idea come true. Encouraged by prior success in applying carbon nitride-supported transition metal (M/g-C 3 N 4 ) into photocatalytic water splitting, [57][58][59][60][61][62][63][64][65] we selected this kind of semiconductor to achieve our goals. It is worth noting that the proton reduction is desired in previous literatures related to M/g-C 3 N 4 -catalyzed water splitting, while this half-reaction would inhibit our reaction [44][45][46][57][58][59][60][61][62][63][64][65] .…”

“…Encouraged by prior success in applying carbon nitride-supported transition metal (M/g-C 3 N 4 ) into photocatalytic water splitting, [57][58][59][60][61][62][63][64][65] we selected this kind of semiconductor to achieve our goals. It is worth noting that the proton reduction is desired in previous literatures related to M/g-C 3 N 4 -catalyzed water splitting, while this half-reaction would inhibit our reaction [44][45][46][57][58][59][60][61][62][63][64][65] . Therefore, the M/g-C 3 N 4 and reaction conditions had to be modified to accelerate the water oxidation and inhibit the proton reduction via a new method, and the results are herein reported.…”

Structure/Property Control in Photocatalytic Organic Semiconductor Nanocrystals

“…Polymeric g‐C 3 N 4 are n‐type semiconductors and show great capabilities in water splitting due to their fairly narrow bandgap and suitable energy levels ( E gap : 2.7 eV, E HOMO : +1.6 V, and E LUMO : −1.1 V). [ 27 ] Other conjugated polymers like PPYs, PTHs or PPyDs possess high excellent conductivity, stability and better control of properties via finer molecular‐level tuning. [ 28 ] MOFs (e.g., porphyrin based MOF) and COFs are appealing for their crystalline porous structures which impart high specific surface area (SSA), ideal channels for high electron and reactant transfer efficiency, as well as their semiconductor‐like role as light‐harvesting antennae.…”

Photocatalytic degradation of tetracycline by Phosphorus-doped carbon nitride tube combined with peroxydisulfate under visible light irradiation

“…However, the application and development of g-CN prepared by the traditional thermal polymerization are strongly restricted by its low specific surface area and the high rate of electronhole recombination (Duan et al 2019). Interestingly, g-CN as an inorganic material, these limitations can be overcome by elemental doping, morphology control, heterojunction, and combination with other AOP methods (Jiang et al 2017;Gao et al 2020;Shen et al 2021;Zhang et al 2021). In the numerous modification methods, morphology control and elemental doping are considered as a fruitful and promising strategies to avoid its disadvantages.…”