Nanostructure Engineering and Doping of Conjugated Carbon Nitride Semiconductors for Hydrogen Photosynthesis

Post-annealing reinforced hollow carbon nitride nanospheres for hydrogen photosynthesis

Hollow-structured g-C3N4 polymers with a high thermal stability up to 550 °C and an enhanced photocatalytic activity have been developed by post-annealing treatment, which effectively modifies the textural, crystal, and electronic properties of the g-C3N4 semiconductors without extra chemical assistance. This is a unique example of thermally and chemically stable conjugated polymers with hollow nanostructures and optoelectronic properties, promising the development of functional hollow g-C3N4 nanocomposites by chemical modifications like doping, surface grafting, and coupling with other inorganic/polymeric semiconductors with the aid of thermal treatment at high temperatures.

Nanoporous photocatalysts developed through heat-driven stacking of graphitic carbon nitride nanosheets

Nanostructured g-C₃N₄ with high surface area from heat treatment of guanidinium cyanurate exhibits better optical properties and enhanced photocatalytic activity.

In situ production of silver nanoparticles on an aldehyde-equipped conjugated porous polymer and subsequent heterogeneous reduction of aromatic nitro groups at room temperature

Silver lining on porous polymer – all from heating Tollen's reagent and a polymer host deriving its versatile functions from pendant aldehyde groups and rigid thioether joints.

Shell-engineering of hollow g-C3N4 nanospheres via copolymerization for photocatalytic hydrogen evolution

Aromatic monomers have been grafted onto photocatalytic hollow carbon nitride nanospheres via copolymerization to strengthen their optical and electronic properties.

Exfoliated carbon nitride nanosheets decorated with NiS as an efficient noble-metal-free visible-light-driven photocatalyst for hydrogen evolution

Exfoliated ultrathin C₃N₄ nanosheets decorated with NiS as a highly efficient visible-light-driven photocatalyst for photoinduced hydrogen evolution.

Recent progress in g-C3N4 based low cost photocatalytic system: activity enhancement and emerging applications

Noble metal free g-C₃N₄ based photocatalysts find promising applications in the fields of photocatalytic H₂ production, overall water splitting and CO₂ reduction. Their photocatalytic can be enhanced by depositing non-noble metal co-catalysts and exfoliation to nanosheets.

Increasing the visible light absorption of graphitic carbon nitride (melon) photocatalysts by homogeneous self-modification with nitrogen vacancies

A novel reduced melon photocatalyst with a bandgap of 2.03 eV developed here has a widened visible light absorption range and suppressed radiative recombination of photo-excited charge carriers due to the homogeneous self-modification with nitrogen vacancies. As a consequence, the reduced melon shows a much superior photocatalytic activity compared to the pristine melon in generating •OH radicals and degrading the organic pollutant Rhodamine B.

Synthesis of potassium-modified graphitic carbon nitride with high photocatalytic activity for hydrogen evolution

Potassium-modified graphitic carbon nitride (K-g-C3N4) nanosheets are synthesized by a facile KCl-template method that holds the advantage of easy removal of residual template. A combination of XRD, X-ray photoelectron spectroscopy, and inductively coupled plasma analyses are utilized to characterize the obtained resultant K-g-C3N4 architectures, which are composed of nanosheets of variable thickness (<10 nm). Photocatalytic hydrogen evolution experiments under visible light irradiation showed that K-g-C3N4 nanosheets have high photocatalytic activities (up to about thirteen times higher than that of pure g-C3 N4 ) as well as good stability (no reduction in activity within 16 h); both features emanate from their unique structural characteristics. These results illustrate the viability of this methodology for the facile synthesis of efficient heterogeneous photocatalysts for potential commercial applications.

Pt-decorated 3D architectures built from graphene and graphitic carbon nitride nanosheets as efficient methanol oxidation catalysts

Homogeneous dispersion of ultrafine Pt nanoparticles on 3D architectures constructed of graphene and exfoliated graphitic carbon nitride results in hybrids with 3D porous structures, large surface area, high nitrogen content, and good electrical conductivity. This leads to excellent electrocatalytic activity, unusually high poison tolerance, and reliable stability for methanol oxidation, making them of interest as catalysts in direct methanol fuel cells.

High efficiency photocatalysis for pollutant degradation with MoS2/C3N4 heterostructures

Porous graphitic carbon nitride was synthesized by controllable thermal polymerization of urea in air. Their textural, electrical, and optical properties were tuned by varying the heating rate. The presence of proper residual oxygen in carbon nitride matrix had enhanced light absorption and inhibited the recombination of charge carriers. Furthermore, the MoS2 nanosheets were coupled into the carbon nitride to form MoS2/C3N4 heterostructures via a facile ultrasonic chemical method. The optimized MoS2/C3N4 heterostructure with 0.05 wt % MoS2 showed a reaction rate constant as high as 0.301 min(-1), which was 3.6 times that of bare carbon nitride. As analyzed by SEM, TEM, UV-vis absorption, PL and photoelectrochemical measurements, intimate contact interface, extended light response range, enhanced separation speed of charge carriers, and high photocurrent density upon MoS2 coupling led to the photocatalytic promotion of the MoS2/C3N4 heterostructures. In this architecture, MoS2 served as electron trapper to extend the lifetime of separated electron-hole pairs. Meanwhile, the accumulated holes on the surface of carbon nitride oxidized the organic dye directly, which was a predominant process in the photodegradation of organic pollutants in water treatment. The promotional mechanisms and principles reported here would have great significance in heterogeneous photocatalysis.

Iodine modified carbon nitride semiconductors as visible light photocatalysts for hydrogen evolution

An optimized and general synthetic strategy based on in-situ iodine modifying of polymeric graphitic carbon nitride is discussed. The as-prepared iodine functionalized g-CN shows enhanced electronic and optical properties, as well as increased photocatalytic activities in an assay of hydrogen evolution.

Influence of g-C3N4 nanosheets on thermal stability and mechanical properties of biopolymer electrolyte nanocomposite films: a novel investigation

A series of sodium alginate (SA) nanocomposite films with different loading levels of graphitic-like carbon nitride (g-C3N4) were fabricated via the casting technique. The structure and morphology of nanocomposite films were investigated by X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. Thermogravimetric analysis results suggested that thermal stability of all the nanocomposite films was enhanced significantly, including initial thermal degradation temperature increased by 29.1 °C and half thermal degradation temperature improved by 118.2 °C. Mechanical properties characterized by tensile testing and dynamic mechanical analysis measurements were also reinforced remarkably. With addition of 6.0 wt % g-C3N4, the tensile strength of SA nanocomposite films was dramatically enhanced by 103%, while the Young's modulus remarkably increased from 60 to 3540 MPa. Moreover, the storage modulus significantly improved by 34.5% was observed at loadings as low as 2.0 wt %. These enhancements were further investigated by means of differential scanning calorimetry and real time Fourier transform infrared spectra. A new perspective of balance was proposed to explain the improvement of those properties for the first time. At lower than 1.0 wt % loading, most of the g-C3N4 nanosheets were discrete in the SA matrix, resulting in improved thermal stability and mechanical properties; above 1.0 wt % and below 6.0 wt % content, the aggregation was present in SA host coupled with insufficient hydrogen bondings limiting the barrier for heat and leading to the earlier degradation and poor dispersion; at 6.0 wt % addition, the favorable balance was established with enhanced thermal and mechanical performances. However, the balance point of 2.0 wt % from dynamic mechanical analysis was due to combination of temperature and agglomeration. The work may contribute to a potential research approach for other nanocomposites.

Facile synthesis of few-layer-thick carbon nitride nanosheets by liquid ammonia-assisted lithiation method and their photocatalytic redox properties

High-quality few-layer-thick graphitic carbon nitride (g-C₃N₄) nanosheets (NSs) were fabricated by a simple, highly efficient, and rapid method namely, liquid ammonia (LA)-assisted lithiation.

Nanosheets of graphitic carbon nitride as metal-free environmental photocatalysts

Nanosheets of g-C₃N₄ with a surface area of 109.9 m² g⁻¹ exhibit better optical properties and enhanced photocatalytic activity.

Synthesis and characterization of the ZnO/mpg-C3N4 heterojunction photocatalyst with enhanced visible light photoactivity

The photocatalytic activity enhancement of the ZnO/mpg-C₃N₄ is due to the high separation and easy transfer of photogenerated electron–hole pairs.

Synthesis of graphene-like g-C3N4/Fe3O4 nanocomposites with high photocatalytic activity and applications in drug delivery

Graphene-like g-C₃N₄ nanosheet/Fe₃O₄ nanocomposites with high photocatalytic activity and applications for magnetically targeted drug delivery.

Two-dimensional g-C3N4: an ideal platform for examining facet selectivity of metal co-catalysts in photocatalysis

Two-dimensional g-C₃N₄ nanosheets with few-layer thickness, ensuring equivalent charge migrations to various Pd facets, provide an ideal model system for examining the facet selectivity of Pd co-catalysts.

Novel visible light-induced g-C3N4 quantum dot/BiPO4 nanocrystal composite photocatalysts for efficient degradation of methyl orange

Novel g-C₃N₄ quantum dot/BiPO₄ nanocrystal heterostructured photocatalysts have been synthesized; the photocatalytic activity for degradation of methyl orange as been significantly improved under visible light (λ > 420 nm) irradiation.

In situ construction of g-C3N4/g-C3N4 metal-free heterojunction for enhanced visible-light photocatalysis

The photocatalytic performance of the star photocatalyst g-C3N4 was restricted by the low efficiency because of the fast charge recombination. The present work developed a facile in situ method to construct g-C3N4/g-C3N4 metal-free isotype heterojunction with molecular composite precursors with the aim to greatly promote the charge separation. Considering the fact that g-C3N4 samples prepared from urea and thiourea separately have different band structure, the molecular composite precursors of urea and thiourea were treated simultaneously under the same thermal conditions, in situ creating a novel layered g-C3N4/g-C3N4 metal-free heterojunction (g-g CN heterojunction). This synthesis method is facile, economic, and environmentally benign using easily available earth-abundant green precursors. The confirmation of isotype g-g CN heterojunction was based on XRD, HRTEM, valence band XPS, ns-level PL, photocurrent, and EIS measurement. Upon visible-light irradiation, the photogenerated electrons transfer from g-C3N4 (thiourea) to g-C3N4 (urea) driven by the conduction band offset of 0.10 eV, whereas the photogenerated holes transfer from g-C3N4 (urea) to g-C3N4 (thiourea) driven by the valence band offset of 0.40 eV. The potential difference between the two g-C3N4 components in the heterojunction is the main driving force for efficient charge separation and transfer. For the removal of NO in air, the g-g CN heterojunction exhibited significantly enhanced visible light photocatalytic activity over g-C3N4 alone and physical mixture of g-C3N4 samples. The enhanced photocatalytic performance of g-g CN isotype heterojunction can be directly ascribed to efficient charge separation and transfer across the heterojunction interface as well as prolonged lifetime of charge carriers. This work demonstrated that rational design and construction of isotype heterojunction could open up a new avenue for the development of new efficient visible-light photocatalysts.

Nanoporous graphitic carbon nitride with enhanced photocatalytic performance

Nanoporous g-C3N4 (npg-C3N4) with high surface area was prepared by a bubble-templating method. A higher calcination heating rate and proportion of thiourea can result in a larger surface area and better adsorption and photodegradation activities of npg-C3N4. Compared with the bulk g-C3N4, the adsorption capacity for the target pollutants and photocatalytic degradation and photocurrent performances under visible light irradiation of npg-C3N4 were greatly improved. The optimal photodegradation activity of npg-C3N4 was 3.4 times as high as that of the bulk g-C3N4. The enhanced activities of npg-C3N4 can be attributed to the larger number of surface active sites, improved separation of photogenerated electron-hole pairs, and higher efficiency of charge immigration.