Moving Graphitic Carbon Nitride from Electrocatalysis and Photocatalysis to a Potential Electrode Material for Photoelectric Devices

Photocatalytic hydrogen evolution based on carbon nitride and organic semiconductors

Photocatalytic hydrogen evolution (PHE) presents a promising way to solve the global energy crisis. Metal-free carbon nitride (CN) and organic semiconductors photocatalysts have drawn intense interests due to their fascinating properties such as tunable molecular structure, electronic states, strong visible-light absorption, low-cost etc. In this paper, the recent progresses of photocatalytic hydrogen production based on organic photocatalysts, including CN, linear polymers, conjugated porous polymers and small molecules, are reviewed, with emphasis on the various strategies to improve PHE efficiency. Finally, the possible future research trends in the organic photocatalysts are prospected.

Sustainable photoanode for water oxidation reactions: from metal-based to metal-free materials

Sunlight affords an inexhaustible and primary energy for Earth. A photoelectrochemical system can efficiently harvest solar energy and convert it into chemicals. However, sophisticated processes and expensive raw materials are...

The Functional Chameleon of Materials Chemistry-Combining Carbon Structures into All-Carbon Hybrid Nanomaterials with Intrinsic Porosity to Overcome the "Functionality-Conductivity-Dilemma" in Electrochemical Energy Storage and Electrocatalysis

Nanoporous carbon materials can cover a remarkably wide range of physicochemical properties. They are widely applied in electrochemical energy storage and electrocatalysis. As a matter of fact, all these applications combine a chemical process at the electrode-electrolyte interface with the transport (and possibly the transfer) of electrons. This leads to multiple requirements which can hardly be fulfilled by one and the same material. This "functionality-conductivity-dilemma" can be minimized when multiple carbon-based compounds are combined into porous all-carbon hybrid nanomaterials. This article is giving a broad and general perspective on this approach from the viewpoint of materials chemists. The problem and existing solutions are first summarized. This is followed by an overview of the most important design principles for such porous materials, a chapter discussing recent examples from different fields where the formation of comparable structures has already been successfully applied, and an outlook over the future development of this field that is foreseen.

Construction of few-layered black phosphorus/graphite-like carbon nitride binary hybrid nanostructure for reducing the fire hazards of epoxy resin

Black phosphorus (BP) and graphite-like carbon nitride (g-C₃N₄) were combined to prepare BP-CN hybrid nanostructure through a simple self-assembly method assisted by ultra-sonication, and as-obtained materials were further used as fire retardants introduced into epoxy resin to fabricate EP/BP-CNx nanocomposites. It was found that the introduction of 2 wt% BP-CNx into EP contributed to considerable decrements in peak heat release rate (up to 47.72%) and total heat release (utmost to 49.60%) of composites, and LOI value increased from 25% to 31%. SSTF results revealed that the introducing of BP-CN can distinctly reduce the production of smoke. TG-IR results demonstrated that the addition of BP-CN0.5 and BP-CN2.0 into EP matrix exert different influences on the decomposition of resin. Analyses of residual chars further validated through adjusting the proportion of BP and CN can achieve different fire performances of matrix. This work illustrates that BP can reduce the fire hazards of EP, and the hybridization of CN can achieve better flame retarded efficiency, which provides a new strategy for black phosphorus to be used as a flame retardant.

Tailoring carbon nitride properties and photoactivity by interfacial engineering of hydrogen-bonded frameworks

The rational synthesis of carbon nitride materials, ranging from polymeric carbon nitride to nitrogen-doped carbon, by supramolecular preorganization of their monomers is a powerful tool for the design of their morphology and photophysical and catalytic activities. Here we show a new facile and scalable approach for the synthesis of ordered CN materials with excellent photoactivity, which consists of supramolecular interfacial preorganization of CN monomers at the interface of two non-miscible solvents. Molecular dynamic simulations supported by experimental results reveal that an appropriate choice of monomers and solvents leads to the formation of a supramolecular assembly solely at the interface of the solvents. As a proof of concept, we show that the properties of the CN materials after thermal condensation can be tuned by adding an additional monomer to one solvent only. The advantages of the new method are demonstrated here through the tunable morphologies and surface area, the formation of new electronic junctions and high activity as a photocatalyst for hydrogen evolution and pollutant degradation of the CN materials.

Physical vapor deposition (PVD): a method to fabricate modified g-C3N4 sheets

We develop a method of physical vapor deposition (PVD) to fabricate modified g-C₃N₄ sheets with abundant defects.

Visible-Light-Driven Chemoselective Hydrogenation of Nitroarenes to Anilines in Water through Graphitic Carbon Nitride Metal-Free Photocatalysis

Green and efficient procedures are essential for the chemoselective hydrogenation of functionalized nitroarenes to form industrially important anilines. Herein, it is shown that visible-light-driven, chemoselective hydrogenation of functionalized nitroarenes with groups sensitive to forming anilines can be achieved in good to excellent yields (82-100 %) in water under relatively mild conditions and catalyzed by low-cost and recyclable graphitic carbon nitride. The process is also applicable to gram-scale reaction, with a yield of aniline of 86 %. A study of the mechanism reveals that visible-light-induced electrons are responsible for the hydrogenation reactions, and thermal energy can also promote the photocatalytic activity. A study of the kinetics shows that this reaction possibly occurs through one-step hydrogenation or stepwise condensation routes. A wide range of applications can be expected for this green, efficient, and highly selective photocatalysis system in reduction reactions for the synthesis of fine chemicals.

Ultrastable g-C3N4 assemblies with high quantum yield and reversible photoluminescence

Ultrastable g-C₃N₄ assemblies consisting of amorphous/crystalline nanosheets with high quantum yields up to 78% were prepared for the first time. A reversible photoluminescence was observed from green to blue once the pH was adjusted. These assemblies exhibit high stability in PL devices.

Molecular engineering of polymeric carbon nitride: advancing applications from photocatalysis to biosensing and more

Different designs and constructions of molecular structures of carbon nitride for emerging applications, such as biosensing, are discussed.

One-Pot Synthesis of Nickel-Modified Carbon Nitride Layers Toward Efficient Photoelectrochemical Cells

A new method to significantly enhance the photoelectrochemical properties of phenyl-modified carbon nitride layers via the insertion of nickel ions into carbon nitride layers is reported. The nickel ions are embedded within the carbon nitride layers by manipulating the interaction of Ni ions and molten organic molecules at elevated temperature prior to their condensation. A detailed analysis of the chemical and photophysical properties suggests that the nickel ions dissolve in the molten molecules, leading to the homogeneous distribution of nickel atoms within the carbon nitride layers. We found that the nickel atoms can alter the growth mechanism of carbon nitride layers, resulting in extended light absorption, charge transfer properties, and the total photoelectrochemical performance. For the most photoactive electrode, the Ni ions have an oxidation state of 2.8, as confirmed by soft X-ray absorption spectroscopy. Furthermore, important parameters such as absorption coefficient, exciton lifetime, and diffusion length were studied in depth, providing substantial progress in our understanding of the photoelectrochemical properties of carbon nitride films. This work opens new opportunities for the growth of carbon nitride layers and similar materials on different surfaces and provides important progress in our understanding of the photophysical and photoelectrochemical properties of carbon nitride layers toward their implantation in photoelectronic and other devices.