Search query: , , , , ,  and , J. Am. Chem. Soc., 2010, 132, 11642–11648

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abstract: Electronic structure intrinsically controls the light absorbance, redox potential, charge carrier mobility, and consequently, photoreactivity of semiconductor photocatalysts. The conventional approach of modifying the electronic structure of a semiconductor photocatalyst for a wider absorption range by anion doping operates at the cost of reduced redox potentials and/or charge carrier mobility, so that its photoreactivity is usually limited and some important reactions may not occur at all. Here, we report sulfur doped graphitic C(3)N(4) (C(3)N(4 x)S(x) with a unique electronic structure that displays an increased valence bandwidth in combination with an elevated conduction band minimum and a slightly reduced absorbance. The C(3)N(4 x)S(x) shows a photoreactivity of H(2) evolution 7.2 and 8.0 times higher than C(3)N(4) under lambda 300 and 420 nm, respectively. More strikingly, the complete oxidation process of phenol under lambda 400 nm can occur for sulfur doped C(3)N(4) which is impossible for C(3)N(4) even under lambda 300 nm. The homogeneous substitution of sulfur for lattice nitrogen and a concomitant quantum confinement effect are identified as the cause of this unique electronic structure and, consequently, the excellent photoreactivity of C(3)N(4 x)S(x) The results acquired may shed light on general doping strategies for designing potentially efficient photocatalysts.
author_names: Gang Liu

Ping Niu

Chenghua Sun

Sean C Smith

Zhigang Chen

Gao Q Lu

Hui-Ming Cheng
title: Unique electronic structure induced high photoreactivity of sulfur doped graphitic C3N4.
venue: Journal of the American Chemical Society
year: 2010

abstract: To develop a highly efficient visible light induced and conveniently recyclable photocatalyst, in this study, a ternary magnetic ZnO/Fe3O4/g C3N4 composite photocatalyst was synthesized for the photodegradation of Monas dye. The structure and optical performance of the composite photocatalyst were characterized using X ray diffraction (XRD) transmission electron microscopye (TEM) energy dispersive spectroscopy (EDS) photoluminescence (PL) spectra, ultraviolet visible diffuse reflection, and photo electrochemistry. The photocatalytic activities of the prepared ZnO/Fe3O4/g C3N4 nanocomposites were notably improved, and they were significantly higher than those of pure g C3N4 and ZnO. Given the presence of the heterojunction between the interfaces of g C3N4 and ZnO, the higher response to visible light and separation efficiency of the photo induced electrons and holes enhanced the photocatalytic activities of the ZnO/Fe3O4/g C3N4 nanocomposites. The stability experiment revealed that ZnO/Fe3O4/g C3N4 50% demonstrates a relatively higher photocatalytic activity after 5 recycles. The degradation efficiency of MO, AYR, and OG over ZnO/Fe3O4/g C3N4 50% were 97.87% 98.05% and 83.35% respectively, which was due to the number of dye molecules adsorbed on the photocatalyst and the structure of the azo dye molecule. Azo dyes could be effectively and rapidly photodegraded by the obtained photocatalyst. Therefore, the environment friendly photocatalyst could be widely applied to the treatment of dye contaminated wastewater.
author_names: Zhansheng Wu

Xiaoqin Chen

Xiaochen Liu

Xia Yang

Yan Yang
title: A Ternary Magnetic Recyclable ZnO/Fe3O4/g C3N4 Composite Photocatalyst for Efficient Photodegradation of Monoazo Dye
venue: Nanoscale Research Letters
year: 2019

abstract: Phosphorus doped hexagonal tubular carbon nitride (P TCN) with the layered stacking structure was obtained from a hexagonal rod like single crystal supramolecular precursor (monoclinic, C2/m) The production process of P TCN involves two steps: 1) the precursor was prepared by self assembly of melamine with cyanuric acid from in situ hydrolysis of melamine under phosphorous acid assisted hydrothermal conditions; 2) the pyrolysis was initiated at the center of precursor under heating, thus giving the hexagonal P TCN. The tubular structure favors the enhancement of light scattering and active sites. Meanwhile, the introduction of phosphorus leads to a narrow band gap and increased electric conductivity. Thus, the P TCN exhibited a high hydrogen evolution rate of 67 mmol h( 1) (0.1 g catalyst, l >420 nm) in the presence of sacrificial agents, and an apparent quantum efficiency of 5.68 at 420 nm, which is better than most of bulk g C3 N4 reported.
author_names: Shien Guo

Zhao-Peng Deng

Mingxia Li

Baojiang Jiang

Chungui Tian

Qingjiang Pan

Honggang Fu
title: Phosphorus Doped Carbon Nitride Tubes with a Layered Micro nanostructure for Enhanced Visible Light Photocatalytic Hydrogen Evolution.
venue: Angewandte Chemie
year: 2016

abstract: Photocatalytic degradation by semiconductors is an ideal way to solve the environmental problem. Here, the porous Mn doped g C3N4 photocatalyst was synthesized by the calcination refluxing method. The as prepared g C3N4 exhibits the high activity of photocatalytic degradation under visible light irradiation 400nm) in the mixed system of Cr(VI) and organic pollutants. Especially, the photocatalytic activity of Cr(VI) reduction was increased from 9.5% to 76.5% while that of Rhodamine B(RhB) degradation was enhanced from 15.3% to 88.9% after 60min irradiation. The porous Mn doped g C3N4 still keeps the high degradation efficiency of mixed pollutants in the 7th running. Based on the computational modeling, the Mn doping and carboxyl modification affect the atomic arrangement and molecular orbital distribution of the g C3N4 semiconductor, leading to the enhancement of photo induced carrier separation. Additionally, the active oxygen species and intermediates in the photoreaction process were discovered by ESR measurement and UV vis test. The RhB degradation in synergistic photocatalysis not only inhibits the reverse reaction of Cr(VI) reduction, but also validly supply the photogenerated electrons by the photosensitization effect. This work may be useful for rationally designing photocatalysts and providing illuminating insights into the photocatalytic mechanism.
author_names: Ji-Chao Wang

Cheng-Xing Cui

Yucheng Li

Lu Liu

Yu-Ping Zhang

Weina Shi
title: Porous Mn doped g C3N4 photocatalysts for enhanced synergetic degradation under visible light illumination.
venue: Journal of hazardous materials
year: 2017

abstract: The primary amine groups on the heptazine based polymer melon, also known as graphitic carbon nitride (g C3N4) can be replaced by urea groups using a two step postsynthetic functionalization. Under simulated sunlight and optimum Pt loading, this urea functionalized carbon nitride has one of the highest activities among organic and polymeric photocatalysts for hydrogen evolution with methanol as sacrificial donor, reaching an apparent quantum efficiency of 18% and nearly 30 times the hydrogen evolution rate compared to the nonfunctionalized counterpart. In the absence of Pt, the urea derivatized material evolves hydrogen at a rate over four times that of the nonfunctionalized one. Since "defects" are conventionally accepted to be the active sites in graphitic carbon nitride for photocatalysis, the work here is a demonstrated example of "defect engineering," where the catalytically relevant defect is inserted rationally for improving the intrinsic, rather than extrinsic, photocatalytic performance. Furthermore, the work provides a retrodictive explanation for the general observation that g C3N4 prepared from urea performs better than those prepared from dicyandiamide and melamine. In depth analyses of the spent photocatalysts and computational modeling suggest that inserting the urea group causes a metal support interaction with the Pt cocatalyst, thus facilitating interfacial charge transfer to the hydrogen evolving centers.
author_names: Vincent Wing-hei Lau

Victor Wen-zhe Yu

Florian Ehrat

Tiago Botari

Igor L Moudrakovski

Thomas Simon

Viola Duppel

Elise Medina

Jacek K Stolarczyk

Jochen Feldmann

Volker Blum

Bettina V Lotsch
title: Urea Modified Carbon Nitrides: Enhancing Photocatalytic Hydrogen Evolution by Rational Defect Engineering
year: 2017

abstract: The major challenge of photocatalytic water splitting, the prototypical reaction for the direct production of hydrogen by using solar energy, is to develop low cost yet highly efficient and stable semiconductor photocatalysts. Herein, an effective strategy for synthesizing extremely active graphitic carbon nitride (g C3N4) from a low cost precursor, urea, is reported. The g C3N4 exhibits an extraordinary hydrogen evolution rate (ca. 20 000 mmol h 1 g 1 under full arc) which leads to a high turnover number (TON) of over 641 after 6 h. The reaction proceeds for more than 30 h without activity loss and results in an internal quantum yield of 26.5 under visible light, which is nearly an order of magnitude higher than that observed for any other existing g C3N4 photocatalysts. Furthermore, it was found by experimental analysis and DFT calculations that as the degree of polymerization increases and the proton concentration decreases, the hydrogen evolution rate is significantly enhanced.
author_names: David James Martin

Kaipei Qiu

Stephen Andrew Shevlin

Albertus Denny Handoko

Xiaowei Chen

Zhengxiao Guo

Junwang Tang
title: Highly Efficient Photocatalytic H2 Evolution from Water using Visible Light and Structure Controlled Graphitic Carbon Nitride*
venue: Angewandte Chemie
year: 2014

abstract: A new type of boron doped graphitic carbon nitride (B g C3N4) nanosheets was prepared by a benign one pot thermal polycondensation process. Systematic studies revealed that a B doping amount of 1 at% into g C3N4 (1at%B g C3N4) showed the best photocatalytic H2 evolution activity of 1880 mmol h 1 g 1 under visible light irradiation >400 nm) which is more than 12 times that of the pristine g C3N4 bulk. Detailed characterizations revealed that the high photocatalytic performance could be attributed to the combination of band structure engineering and morphological control. B doping not only reduces the band gap to absorb more visible light but also exhibits a higher surface area of B g C3N4 (49.47 m2 g 1) as compared to that of g C3N4 bulk (8.24 m2 g 1) which subsequently improve the photocatalytic performance drastically. This work demonstrates a synergistic strategy to prepare efficient metal free B g C3N4 nanosheets as a promising photocatalyst for H2 evolution under visible light with good stability.
author_names: Supphasin Thaweesak

Songcan Wang

Miaoqiang Lyu

Mu Xiao

Piangjai Peerakiatkhajohn

Lianzhong Wang
title: Boron doped graphitic carbon nitride nanosheets for enhanced visible light photocatalytic water splitting.
venue: Dalton transactions
year: 2017

abstract: Graphitic carbon nitride (g C(3)N(4) as an intriguing earth abundant visible light photocatalyst, possesses a unique two dimensional structure, excellent chemical stability and tunable electronic structure. Pure g C(3)N(4) suffers from rapid recombination of photo generated electron hole pairs resulting in low photocatalytic activity. Because of the unique electronic structure, the g C(3)N(4) could act as an eminent candidate for coupling with various functional materials to enhance the performance. According to the discrepancies in the photocatalytic mechanism and process, six primary systems of g C(3)N(4) based nanocomposites can be classified and summarized: namely, the g C(3)N(4) based metal free heterojunction, the g C(3)N(4)/single metal oxide (metal sulfide) heterojunction, g C(3)N(4)/composite oxide, the g C(3)N(4)/halide heterojunction, g C(3)N(4)/noble metal heterostructures, and the g C(3)N(4) based complex system. Apart from the depiction of the fabrication methods, heterojunction structure and multifunctional application of the g C(3)N(4) based nanocomposites, we emphasize and elaborate on the underlying mechanisms in the photocatalytic activity enhancement of g C(3)N(4) based nanocomposites. The unique functions of the p n junction (semiconductor/semiconductor heterostructures) the Schottky junction (metal/semiconductor heterostructures) the surface plasmon resonance (SPR) effect, photosensitization, superconductivity, etc. are utilized in the photocatalytic processes. Furthermore, the enhanced performance of g C(3)N(4) based nanocomposites has been widely employed in environmental and energetic applications such as photocatalytic degradation of pollutants, photocatalytic hydrogen generation, carbon dioxide reduction, disinfection, and supercapacitors. This critical review ends with a summary and some perspectives on the challenges and new directions in exploring g C(3)N(4) based advanced nanomaterials.
author_names: Zaiwang Zhao

Yanjuan Sun

Fan Dong
title: Graphitic carbon nitride based nanocomposites: a review.
venue: Nanoscale
year: 2015

abstract: A heterogeneous WS2/g C3N4 composite photocatalyst was prepared by a facile ultrasound assisted hydrothermal method. The WS2/g C3N4 composite was used for photocatalytic regeneration of NAD+ to NADH, which were coupled with dehydrogenases for sustainable bioconversion of CO2 to methanol under visible light irradiation. Compared with pristine g C3N4 and the physical mixture of WS2 and g C3N4, the fabricated WS2/g C3N4 composite catalyst with 5 wt% of WS2 showed the highest activity for methanol synthesis. The methanol productivity reached 372.1 mmol h 1 gcat 1, which is approximately 7.5 times higher than that obtained using pure g C3N4. For further application demonstration, the activity of the WS2/g C3N4 composite catalyst toward photodegradation of Rhodamine B (RhB) was evaluated. RhB removal ratio approaching 100% was achieved in 1 hour by using the WS2/g C3N4 composite catalyst with 5 wt% of WS2, at an apparent degradation rate approximately 2.6 times higher than that of pure g C3N4. Based on detailed investigations on physiochemical properties of the photocatalysts, the significantly enhanced reaction efficiency of the WS2/g C3N4 composite was considered to be mainly benefiting from the formation of a heterojunction interface between WS2 and g C3N4. Upon visible light irradiation, the photo induced electrons can transfer from the conduction band of g C3N4 to WS2, thus recombination of electrons and holes was decreased and the photo harvesting efficiency was enhanced.
author_names: Peng Zeng

Xiaoyuan Ji

Zhi-guo Su

Songping Zhang
title: WS2/g C3N4 composite as an efficient heterojunction photocatalyst for biocatalyzed artificial photosynthesis
year: 2018

abstract: Novel photocatalysts CdSe quantum dots (QDs)/g C3N4 were successfully constructed. The structure, chemical composition, and optical properties of the prepared samples were investigated via a series of characterization techniques. The results indicated that CdSe QDs/g C3N4 photocatalysts exhibited remarkably enhanced photocatalytic activity for visible light induced H2 evolution compared to pristine g C3N4 and CdSe QDs and addition of 13.6 wt CdSe QDs into the composite photocatalyst generated the highest H2 production rate. The enhanced photocatalytic performance of CdSe QDs/g C3N4 can be attributed to the synergistic effects of excellent visible absorption and high charge separation efficiency from the heterostructure. This work could not only provide a facile method to fabricate semiconductor QDs modified g C3N4 photocatalysts but also contribute to the design for heterostructures.
author_names: Yunqian Zhong

Weiwei Chen

Shan Yu

Zhang-hui Xie

Shiqiang Wei

Ying Zhou
title: CdSe Quantum Dots/g C3N4 Heterostructure for Efficient H2 Production under Visible Light Irradiation
venue: ACS omega
year: 2018