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abstract: As a fascinating conjugated polymer, graphitic carbon nitride (g C3N4) has become a new research hotspot and drawn broad interdisciplinary attention as a metal free and visible light responsive photocatalyst in the arena of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability, and "earth abundant" nature. This critical review summarizes a panorama of the latest progress related to the design and construction of pristine g C3N4 and g C3N4 based nanocomposites, including (1) nanoarchitecture design of bare g C3N4, such as hard and soft templating approaches, supramolecular preorganization assembly, exfoliation, and template free synthesis routes, (2) functionalization of g C3N4 at an atomic level (elemental doping) and molecular level (copolymerization) and (3) modification of g C3N4 with well matched energy levels of another semiconductor or a metal as a cocatalyst to form heterojunction nanostructures. The construction and characteristics of each classification of the heterojunction system will be critically reviewed, namely metal g C3N4, semiconductor g C3N4, isotype g C3N4/g C3N4, graphitic carbon g C3N4, conducting polymer g C3N4, sensitizer g C3N4, and multicomponent heterojunctions. The band structures, electronic properties, optical absorption, and interfacial charge transfer of g C3N4 based heterostructured nanohybrids will also be theoretically discussed based on the first principles density functional theory (DFT) calculations to provide insightful outlooks on the charge carrier dynamics. Apart from that, the advancement of the versatile photoredox applications toward artificial photosynthesis (water splitting and photofixation of CO2) environmental decontamination, and bacteria disinfection will be presented in detail. Last but not least, this comprehensive review will conclude with a summary and some invigorating perspectives on the challenges and future directions at the forefront of this research platform. It is anticipated that this review can stimulate a new research doorway to facilitate the next generation of g C3N4 based photocatalysts with ameliorated performances by harnessing the outstanding structural, electronic, and optical properties for the development of a sustainable future without environmental detriment.
author_names: Wee-Jun Ong

Lling-Lling Tan

Yun Hau Ng

Siek-Ting Yong

Siang-Piao Chai
title: Graphitic Carbon Nitride (g C3N4) Based Photocatalysts for Artificial Photosynthesis and Environmental Remediation: Are We a Step Closer To Achieving Sustainability?
venue: Chemical reviews
year: 2016

abstract: Abstract Herein, two dimensional (2D) TiO2 mesoporous nanosheets with three to four C3N4 layers grown in situ are employed to design a core shell 2D/2D van der Waals heterojunction (TiO2/C3N4) Edge terminated zero dimensional (0D) Ti3C2 MXene quantum dots (TCQD) are subsequently integrated in the C3N4 surface via electrostatic interactions. The constructed 2D/2D/0D TiO2/C3N4/Ti3C2 composite heterojunction photocatalyst exhibits enhanced CO2 reduction activity compared to TiO2, C3N4, TiO2/C3N4, C3N4/Ti3C2 for CO and CH4 production. A step scheme (S scheme) charge transfer mechanism operates for the prepared samples during CO2 reduction, as authenticated by in situ X ray photoelectron spectroscopy and electron paramagnetic resonance analysis. This study provides a paradigm of a rational structural design for regulating the number and type of heterointerfaces and further insights into the mechanism of multijunction photocatalysts.
author_names: Fei-Feng He

Bicheng Zhu

Bei Cheng

Jiaguo Yu

Wingkei Ho

Wojciech Macyk
title: 2D/2D/0D TiO2/C3N4/Ti3C2 MXene composite S scheme photocatalyst with enhanced CO2 reduction activity
year: 2020

abstract: Abstract Designing carbonaceous materials modified g C3N4 based photocatalytic system with broadband solar absorption from the visible to near infrared (NIR) region for photocatalytic H2 evolution (PHE) remains a big challenge. Herein, urea formaldehyde resin carbonized nitrogen doped carbon (UFR NC) ribbons modified g C3N4 nanosheets were prepared by a facile thermal treatment method. Experimental results imply that g C3N4/UFR NC composites not only show larger specific surface area (SSA) better crystallinity and outstanding stability but also exhibit faster separation of charge carriers, in which the UFR NC ribbons are more apt to accept electrons. Additionally, g C3N4/UFR NC composites possess superior optical adsorption from visible to NIR light and the band gap can be easily adjusted by changing the content of UFR NC ribbons. Surprisingly, g C3N4/UFR NC0.02 exhibits the highest PHE activity (84.32 umol h 1) which is over 54.75 and 6.51 times higher than that of the g C3N4 obtained by direct calcination of melamine (g C3N4 M) and direct calcination of urea (g C3N4 U) under visible light, and the apparent quantum efficiency (AQE) reaches 6.2% at 420 nm. In addition, the g C3N4/UFR NC0.02 displays an enhanced PHE activity of 26.59 umol h 1 and 0.45 umol h 1 under the blue visible (l 475 nm) and NIR light irradiation (l 800 nm) And the PHE activity of g C3N4/UFR NC0.02 has no obvious change after fourteen runs within 70 h. Our results suggest that constructing carbonaceous materials modified g C3N4 based photocatalytic system will be a promising strategy to PHE.
author_names: Huinan Che

Guangbo Che

Pengjie Zhou

Chunbo Liu

Hongjun Dong

Chunxue Li

Ning Song

Chunmei Li
title: Nitrogen doped carbon ribbons modified g C3N4 for markedly enhanced photocatalytic H2 production in visible to near infrared region
year: 2020

abstract: Abstract To efficiently facilitate the charge transfer by constructing heterojunction photocatalysts is a promising strategy for improving solar driven hydrogen generation. Herein, a novel 2D/2D nanojunction architecture of Ba5Nb4O15/g C3N4 photocatalysts with powerful interfacial charge transfer are rationally designed. Advanced electron microscopy analysis elucidates the layered hexagonal nanosheets were coupled on the surface of ultrathin g C3N4 forming a 2D/2D nanojunction. More importantly, such characterizations and theoretical calculations together illustrate that a strong interfacial charge transfer existed between the g C3N4 layer and Ba O layer of the Ba5Nb4O15 nanosheets, which fostered the efficient transfer and provided more massive reactive centers for photocatalytic hydrogen evolution. The unique 2D/2D structure in Ba5Nb4O15/g C3N4 heterojunction leads to generate numerous charge transfer nanochannels, and which could accelerate the interfacial charge separation efficiency to a great extent. Ba5Nb4O15/g C3N4 (1:20) sample displayed a remarkable photocatalytic H2 evolution rate (2.67 mmol h 1 g 1) in oxalic acid solution, nearly 2.35 times higher than that of single g C3N4 under visible light and exhibits an outstanding photostability even after four cycles. This work would provide a new insight for the design of 2D/2D heterojunction photocatalyst with efficient interfacial charge transfer and separation for solar to H2 conversion.
author_names: Kai Wang

Yuan Li

Jun Li

Gaoke Zhang
title: Boosting interfacial charge separation of Ba5Nb4O15/g C3N4 photocatalysts by 2D/2D nanojunction towards efficient visible light driven H2 generation
year: 2020

abstract: Abstract By heating g C3N4 powder in the hydrogen atmosphere, nitrogen defects were introduced into the framework of g C3N4 where the nitrogen atoms in g C3N4 were reacted and partially removed with hydrogen. The effects of nitrogen defects on the electronic structure, optical properties, generation of reactive oxygen species and photocatalytic NO oxidation of g C3N4 were investigated by combining experimental characterization and DFT theoretical calculations. The N defect is located at N2C sites and can be tuned by the H2 treating temperature. The obtained N defective g C3N4 products possessed narrower bandgap adjusted by surface N defects and were able to promote the separation of photoexcited charge carries and produce reactive oxygen species more efficiently than pristine g C3N4. The NO+ reaction intermediate was formed on the N defects sites and enabled an accelerated photocatalytic reaction that contributed to enhanced photocatalytic NO removal. The NO removal ratio on N defects g C3N4 obtained at 600 degC (CH H 600) was 2.6 times that of pristine g C3N4 under visible light irradiation. The present work could provide new insights into the understanding of the role of N defects in g C3N4 and application of photocatalytic technology for efficient air purification.
author_names: Jiazhen Liao

Wenquan Cui

Jieyuan Li

Jianping Sheng

Hong Wang

Xing'an Dong

Peng Chen

Guangming Jiang

Zhiming M Wang

Fan Dong
title: Nitrogen defect structure and NO+ intermediate promoted photocatalytic NO removal on H2 treated g C3N4
year: 2020

abstract: A graphite carbon nitride (g C3N4) modified Bi4O5I2 composite was successfully prepared in situ via the thermal treatment of a g C3N4/BiOI precursor at 400degC for 3 hr. The as prepared g C3N4/Bi4O5I2 showed high photocatalytic performance in Methyl Orange (MO) degradation under visible light. The best sample presented a degradation rate of 0.164 min 1, which is 3.2 and 82 times as high as that of Bi4O5I2 and g C3N4, respectively. The g C3N4/Bi4O5I2 was characterized by X ray powder diffractometer (XRD) scanning electron microscopy (SEM) transmission electron microscopy (TEM) Raman, X ray photoelectron spectroscopy (XPS) ultraviolet visible diffuse reflectance spectra (DRS) electrochemical impedance spectroscopy (EIS) and transient photocurrent response in order to explain the enhanced photoactivity. Results indicated that the decoration with a small amount of g C3N4 influenced the specific surface area only slightly. Nevertheless, the capability for absorbing visible light was improved measurably, which was beneficial to the MO degradation. On top of that, a strong interaction between g C3N4 and Bi4O5I2 was detected. This interplay promoted the formation of a favorable heterojunction structure and thereby enhanced the charge separation. Thus, the g C3N4/Bi4O5I2 composite presented greater charge separation efficiency and much better photocatalytic performance than Bi4O5I2. Additionally, g C3N4/Bi4O5I2 also presented high stability. *O2 and holes were verified to be the main reactive species.
author_names: Zhe-sheng Feng

Lin Zeng

Qingle Zhang

Shifeng Ge

Xinyue Zhao

Hongjun Lin

Yiming He
title: In situ preparation of g C3N4/Bi4O5I2 complex and its elevated photoactivity in Methyl Orange degradation under visible light.
venue: Journal of environmental sciences
year: 2020

abstract: Abstract Z scheme type photocatalysts with two photochemical systems of graphic C3N4 (g C3N4) and anatase TiO2 (A TiO2) nanocrystals combined with Au nanoparticles (NPs) (Au/A TiO2)@g C3N4] were successfully fabricated. The surface heterojunction between coexposed {001} and {101} facets in A TiO2 nanocrystals improves separation efficiency of photoelectrons and holes. Supported Au NPs gather and transfer the stimulated electrons originated from A TiO2 to g C3N4. Wrapped g C3N4 nanosheets can not only trap the photoelectrons, but also its surface p bond can improve adsorption capabilities for CO2. (Au/A TiO2)@g C3N4 catalysts with enriched surface photoelectrons and CO2 exhibit high photocatalytic activity for visible light driven conversion of CO2, i.e. the formation rates of CH4 and CO over (Au/A TiO2)@C3N4 5 catalyst are 37.4 and 21.7 mmol g 1 h 1, respectively. The selectivity for CO2 reduction is higher than 99% and the selectivity of CH4 product increases from 1.4% to 63.3% The innovation of Z scheme type photocatalysts is expected to provide new inspiration for artificial simulation photosynthesis.
author_names: Chujun Wang

Yilong Zhao

Hui Xu

Yifei Li

Yuechang Wei

Jian Liu

Zhen Zhao
title: Efficient Z scheme photocatalysts of ultrathin g C3N4 wrapped Au/TiO2 nanocrystals for enhanced visible light driven conversion of CO2 with H2O
year: 2020

abstract: With the fast development of industrial and human activity, large amounts of persistent organic pollutants, heavy metal ions and radionuclides are released into the natural environment, which results in environmental pollution. The efficient elimination of the natural environment is crucial for the protection of environment to against the pollutants' toxicity to human beings and living organisms. Graphitic carbon nitride (g C3N4) has drawn multidisciplinary attention especially in environmental pollutants' cleanup due to its special physicochemical properties. In this review, we summarized the recent works about the synthesis of g C3N4, element doping, structure modification of g C3N4 and g C3N4 based materials, and their application in the sorption, photocatalytic degradation and reduction solidification of persistent organic pollutants and heavy metal ions. The interaction mechanisms were discussed from advanced spectroscopic analysis and computational approaches at molecular level. The challenges and future perspectives of g C3N4 based materials' application in environmental pollution management are presented in the end. This review highlights the real applications of g C3N4 based materials as adsorbents or photocatalysts in the adsorption reduction solidification of metal ions or photocatalytic degradation of organic pollutants. The contents are helpful for the undergraduate students to understand the recent works in the elimination of organic/inorganic pollutants in their pollution management.
author_names: Zhongshan Chen

Sai Zhang

Yang Liu

Njud Saleh Alharbi

Samar Omar Rabah

Suhua Wang

Xiangxue Wang
title: Synthesis and fabrication of g C3N4 based materials and their application in elimination of pollutants.
venue: The Science of the total environment
year: 2020

abstract: Abstract In this paper, an ultrathin 2D/2D Ti3C2/g C3N4 heterojunction was synthesized by direct calcination the mixture of bulk Ti3C2 and urea, where urea not only acts as the gas template to exfoliate Ti3C2 into nanosheets, but also as the precursor of g C3N4 to craft Ti3C2/g C3N4 heterojunction. CO2 photoreduction activity tests reveal that pure g C3N4 (UCN) exhibits very weak photoactivity. However, when Ti3C2 was coupled with g C3N4, the photocatalytic performance is soaringly enhanced. The optimal sample (10TC) shows the yields of 5.19 and 0.044 mmol h 1 g 1 for CO and CH4, respectively, and the total CO2 conversion is 8.1 times higher than that of UCN. The enhanced CO2 photoreduction activity is mainly attributed to the combined effects of (1) improved CO2 adsorption and activation, and (2) the construction of ultrathin 2D/2D Ti3C2/g C3N4 heterojunction, where the intimate contact stimulates an efficient spatial separation of photo excited charge carriers.
author_names: Chao Yang

Qiuyang Tan

Qin Li

Jie Zhou

Jiajie Fan

Bo Li

Jie Sun

Kangle Lv
title: 2D/2D Ti3C2 MXene/g C3N4 nanosheets heterojunction for high efficient CO2 reduction photocatalyst: Dual effects of urea
year: 2020

abstract: Abstract The photocatalytic overall water splitting is an ideal pathway to generate hydrogen gas for sustainable energy production. Herein, the 2D/2D Co3(PO4)2/g C3N4 heterojunctions were successfully synthesized for overall water splitting from pure water by a simple direct precipitation route under the effect of coulomb electrostatic interaction. The introduction of Co3(PO4)2 nanosheets broadens the light absorption range of Co3(PO4)2/g C3N4 heterojunction, and in addition, the unusual 2D/2D heterostructure can provide more contact areas to promote the interfacial charge transfer between g C3N4 nanosheets and Co3(PO4)2 nanosheets, which considerably enhances the photogenerated charge separation. Among the Co3(PO4)2/g C3N4 heterojunctions, 35% Co3(PO4)2/g C3N4 exhibits the optimal H2 and O2 evolution rates which are 375.6 and 177.4 mmol g 1 h 1, respectively. Moreover, the apparent quantum efficiency of the 35% Co3(PO4)2/g C3N4 reaches up to 1.32% at 420 nm. Furthermore, the 2D/2D Co3(PO4)2/g C3N4 composite possesses the prominent stability and recyclability, testifying a potential application for the conversion of the sustainable energy.
author_names: Weilong Shi

Mingyang Li

Xiliu Huang

Hongji Ren

Chao Yan

Feng Guo
title: Facile synthesis of 2D/2D Co3(PO4)2/g C3N4 heterojunction for highly photocatalytic overall water splitting under visible light
year: 2020