Enhancement of the Photocatalytic Activity of Carbon Nitrides by Complex Templating

The graphitic carbon nitride (g-C3N4) materials have been synthesized from nitrogen rich precursors such as urea and thiourea by directly heating at 520 °C for 2 h. The as-synthesized carbon nitride samples were characterized by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible (UV-vis) absorption spectroscopy, photoluminescence (PL) and particle size analysis. The photoelectrochemical measurements were performed using several on-off cycles under visible-light irradiation. The x-ray diffraction peak is broader which indicates the fine powder nature of the synthesized materials. The estimated crystallite size of carbon nitrides synthesized from urea (U-CN) and thiourea (T-CN) are 4.0 and 4.4 nm respectively. The particle size of U-CN and T-CN were analysed by particle size analyser and were found to be 57.3 and 273.3 nm respectively. The photocatalytic activity for the degradation of the textile dye namely, direct red-81 (DR81) using these carbon nitrides were carried out under visible light irradiation. In the present investigation, a comparison study on the carbon nitrides synthesized from cheap precursors such as urea and thiourea for the degradation of DR81 has been carried out. The results inferred that U-CN exhibited higher photocatalytic activity than T-CN. The photoelectrochemical studies confirmed that the (e--h+) charge carrier separation is more efficient in U-CN than that of T-CN and therefore showed high photocatalytic degradation. Further, the smaller particle size of U-CN is also responsible for the observed degradation trend.

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Conductivity mechanism in ionic 2D carbon nitrides: from hydrated ion motion to enhanced photocatalysis

10.33774/chemrxiv-2021-zb25v ◽

2021 ◽

Author(s):

Julia Kröger ◽

Filip Podjaski ◽

Gökçen Savaşçı ◽

Igor Moudrakovski ◽

Alberto Jimenez-Solano ◽

...

Keyword(s):

Photocatalytic Activity ◽

Ionic Conductivity ◽

Charge Carrier ◽

Pore Channel ◽

Ion Motion ◽

Carrier Lifetimes ◽

Carbon Nitrides ◽

Efficient Charge ◽

Mobile Ions ◽

Hydrated Ion

Carbon nitrides are among the most studied materials for photocatalysis, however, limitations arise from inefficient charge separation and transport within the material. Here, this aspect is addressed in the 2D carbon nitride poly(heptazine imide) (PHI) by investigating the influence of various counterions, such as M = Li+, Na+, K+, Cs+, Ba2+, NH4+ and tetramethyl ammonium, on the material’s conductivity and photocatalytic activity. These ions in the PHI pores affect the stacking of the 2D layers, which further influences the predominantly ionic conductivity in M-PHI. Na-containing PHI outperforms the other M-PHI in various relative humidity (RH) environments (0-42 %RH) in terms of conductivity, likely due to pore channel geometry and size of the (hydrated) ion. With increasing RH, the ionic conductivity increases by 4-5 orders of magnitude (for Na-PHI up to 10-5 S cm-1 at 42 %RH). At the same time, the highest photocatalytic hydrogen evolution rate is observed for Na-PHI, which is mirrored by increased photo-generated charge carrier lifetimes, pointing to efficient charge carrier stabilization by mobile ions. These results indicate that ionic conductivity is an important parameter that can influence the photocatalytic activity. Besides, RH-dependent ionic conductivity is of high interest for separators, membranes, or sensors.

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Carbon nitrides modified with suitable electron withdrawing groups enhancing the visible-light-driven photocatalytic activity for degradation of the Rhodamine B

Materials Research Bulletin ◽

10.1016/j.materresbull.2018.06.008 ◽

2018 ◽

Vol 106 ◽

pp. 204-212 ◽

Cited By ~ 1

Author(s):

Jinpeng Yang ◽

Yijun Yin ◽

Huimin Heng ◽

Pengcheng Meng ◽

Yanhong Sun ◽

...

Keyword(s):

Photocatalytic Activity ◽

Visible Light ◽

Rhodamine B ◽

Carbon Nitrides ◽

Visible Light Driven

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Mesoporous Metal-Containing Carbon Nitrides for Improved Photocatalytic Activities

Journal of Chemistry ◽

10.1155/2013/945348 ◽

2013 ◽

Vol 2013 ◽

pp. 1-6 ◽

Cited By ~ 9

Author(s):

Jie Luo ◽

Zhao-Jie Cui ◽

Guo-Long Zang

Keyword(s):

Photocatalytic Activity ◽

Mesoporous Structure ◽

Hard Template ◽

Visible Absorption ◽

Contaminant Degradation ◽

Photocatalytic Activities ◽

Carbon Nitrides ◽

Uv Visible ◽

Mesoporous Metal ◽

Positive Effect

Graphitic carbon nitrides (g-C3N4) have attracted increasing interest due to their unusual properties and promising applications in water splitting, heterogeneous catalysis, and organic contaminant degradation. In this study, a new method was developed for the synthesis of mesoporous Fe contained g-C3N4(m-Fe-C3N4) photocatalyst by using SiO2nanoparticles as hard template and dicyandiamide as precursor. The physicochemical properties of m-Fe-C3N4were thoroughly investigated. The XRD and XPS results indicated that Fe was strongly coordinated with the g-C3N4matrix and that the doping and mesoporous structure partially deteriorated its crystalline structure. The UV-visible absorption spectra revealed that m-Fe-C3N4with a unique electronic structure displays an increased band gap in combination with a slightly reduced absorbance, implying that mesoporous structure modified the electronic properties of g-Fe-C3N4. The photocatalytic activity of m-Fe-C3N4for photodegradation of Rhodamine B (RhB) was much higher than that of g-Fe-C3N4, clearly demonstrating porous structure positive effect.

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Design of melem-based supramolecular assemblies for the synthesis of polymeric carbon nitrides with enhanced photocatalytic activity

Journal of Materials Chemistry A ◽

10.1039/d1ta05450c ◽

2021 ◽

Author(s):

Jiawei Xia ◽

Neeta Karjule ◽

Biswajit Mondal ◽

Jiani Qin ◽

Michael Volokh ◽

...

Keyword(s):

Photocatalytic Activity ◽

Carbon Nitride ◽

Supramolecular Assembly ◽

Supramolecular Assemblies ◽

Carbon Nitrides ◽

Polymeric Carbon

We design a new supramolecular assembly family as reactants to synthesize highly-photoactive porous polymeric carbon nitride (CN), based on a melem-constructed honeycomb, coupled with the insertion of small triazine analogs....

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Morphology Control in 2D Carbon Nitrides: Impact of Particle Size on Optoelectronic Properties and Photocatalysis

10.26434/chemrxiv.14346194.v1 ◽

2021 ◽

Author(s):

Julia Kröger ◽

Alberto Jiménez-Solano ◽

Gökcen Savasci ◽

Vincent Wing-hei Lau ◽

Viola Duppel ◽

...

Keyword(s):

Particle Size ◽

Photocatalytic Activity ◽

Hydrogen Evolution ◽

Carbon Nitride ◽

Colloidal Stability ◽

Photophysical Properties ◽

Trap States ◽

Time Resolved ◽

Transport Studies ◽

Carbon Nitrides

The carbon nitride poly(heptazine imide), PHI, has recently emerged as a powerful 2D carbon nitride photocatalyst with intriguing charge storing ability. Yet, insights into how morphology, particle size and defects influence its photophysical properties are virtually absent. Here, ultrasonication is used to systematically tune the particle size as well as concentration of surface functional groups and study their impact. Enhanced photocatalytic activity correlates with an optimal amount of those defects that create shallow trap states in the optical band gap, promoting charge percolation, as evidenced by time-resolved photoluminescence spectroscopy, charge transport studies, and quantum-chemical calculations. Excessive amounts of terminal defects can act as recombination centers and hence, decrease the photocatalytic activity for hydrogen evolution. Re-agglomeration of small particles can, however, partially restore the photocatalytic activity. The type and amount of trap states at the surface can also influence the deposition of the co-catalyst Pt, which is used in hydrogen evolution experiments. Optimized conditions entail improved Pt distribution, as well as an enhanced wettability and colloidal stability. A description of the interplay between these effects is provided to obtain a holistic picture of the size–property–activity relationship in nanoparticulate PHI-type carbon nitrides that can likely be generalized to related photocatalytic systems.<br>

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Morphology Control in 2D Carbon Nitrides: Impact of Particle Size on Optoelectronic Properties and Photocatalysis

10.26434/chemrxiv.14346194 ◽

2021 ◽

Author(s):

Julia Kröger ◽

Alberto Jiménez-Solano ◽

Gökcen Savasci ◽

Vincent Wing-hei Lau ◽

Viola Duppel ◽

...

Keyword(s):

Particle Size ◽

Photocatalytic Activity ◽

Hydrogen Evolution ◽

Carbon Nitride ◽

Colloidal Stability ◽

Photophysical Properties ◽

Trap States ◽

Time Resolved ◽

Transport Studies ◽

Carbon Nitrides

The carbon nitride poly(heptazine imide), PHI, has recently emerged as a powerful 2D carbon nitride photocatalyst with intriguing charge storing ability. Yet, insights into how morphology, particle size and defects influence its photophysical properties are virtually absent. Here, ultrasonication is used to systematically tune the particle size as well as concentration of surface functional groups and study their impact. Enhanced photocatalytic activity correlates with an optimal amount of those defects that create shallow trap states in the optical band gap, promoting charge percolation, as evidenced by time-resolved photoluminescence spectroscopy, charge transport studies, and quantum-chemical calculations. Excessive amounts of terminal defects can act as recombination centers and hence, decrease the photocatalytic activity for hydrogen evolution. Re-agglomeration of small particles can, however, partially restore the photocatalytic activity. The type and amount of trap states at the surface can also influence the deposition of the co-catalyst Pt, which is used in hydrogen evolution experiments. Optimized conditions entail improved Pt distribution, as well as an enhanced wettability and colloidal stability. A description of the interplay between these effects is provided to obtain a holistic picture of the size–property–activity relationship in nanoparticulate PHI-type carbon nitrides that can likely be generalized to related photocatalytic systems.<br>

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