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A primary method for the production of 2D nanosheets is liquid-phase delamination from their 3D layered bulk analogues. Most strategies currently achieve this objective by significant mechanical energy input or chemical modification but these processes are detrimental to the structure and properties of the resulting 2D nanomaterials. Bulk poly(triazine imide) (PTI)-based carbon nitrides are layered materials with a high degree of crystalline order. Here, we demonstrate that these semiconductors are spontaneously soluble in select polar aprotic solvents, that is, without any chemical or physical intervention. In contrast to more aggressive exfoliation strategies, this thermodynamically driven dissolution process perfectly maintains the crystallographic form of the starting material, yielding solutions of defect-free, hexagonal 2D nanosheets with a well-defined size distribution. This pristine nanosheet structure results in narrow, excitation-wavelength-independent photoluminescence emission spectra. Furthermore, by controlling the aggregation state of the nanosheets, we demonstrate that the emission wavelengths can be tuned from narrow UV to broad-band white. This has potential applicability to a range of optoelectronic devices.

Polymer electrolyte fuel cells (PEFCs) are a promising replacement for the fossil fuel–dependent automotive and energy sectors. They have become increasingly commercialized in the last decade; however, significant limitations on durability and performance limit their commercial uptake. Catalyst layer (CL) design is commonly reported to impact device power density and durability; although, a consensus is rarely reached due to differences in testing conditions, experimental design, and types of data reported. This is further exacerbated by aspects of CL design such as catalyst support, proton conduction, catalyst, fabrication, and morphology, being significantly interdependent; hence, a wider appreciation is required in order to optimize performance, improve durability, and reduce costs. Here, the cutting‐edge research within the field of PEFCs is reviewed, investigating the effect of different manufacturing techniques, electrolyte distribution, support materials, surface chemistries, and total porosity on power density and durability. These are critically appraised from an applied perspective to inform the most relevant and promising pathways to make and test commercially viable cells. This holistic view of the competing aspects of CL design and preparation will facilitate the development of optimized CLs, especially the incorporation of novel catalyst support materials.

Crystalline layered carbon nitrides can be inter-converted by simple ion exchange process allowing their properties to be tuned.

Dark-colored shiny flakes of graphitic carbon nitride materials produced by reacting dicyandiamide C2N4H4 in a KBr/LiBr molten salt medium were determined to have a C/N ratio near 1.2:1. The compounds also contained 2.3–2.5 wt % H incorporated within N–H species identified by Fourier transform infrared spectroscopy. One recent study revealed analogous results for thin films produced by an similar synthesis method, while a previous investigation instead reported formation of crystalline gC3N4 flakes with a triazine-based graphitic carbon nitride (TGCN) structure. The structures of the materials produced here were studied using a combination of high resolution transmission electron microscopy, X-ray diffraction, IR and Raman and X-ray photoelectron spectroscopy, along with series of density functional theory (DFT) calculations carried out for a range of model layered structures. The results indicate the graphitic layered gC x N y materials contain a mixture of sp2-hybridized C–N and C–C bonded structures, with TGCN to graphene-like domains existing within the layers. Paramagnetic centers localized on the C3N3 rings revealed by electron paramagnetic resonance spectroscopy correspond to potential defect structures within the graphitic layers predicted by DFT calculations. Our results combined with those of previous researchers indicate that a range of graphitic carbon nitride materials could exist with different C/N/H ratios leading to tunable electronic properties for catalysis, semiconducting, spintronics and energy applications, that could be targeted by controlling the synthesis and thin film deposition procedures.

Designing next-generation fuel cell and filtration devices requires the development of nanoporous materials that allow rapid and reversible uptake and directed transport of water molecules. Here, we combine neutron spectroscopy and first-principles calculations to demonstrate rapid transport of molecular H2O through nanometer-sized voids ordered within the layers of crystalline carbon nitride with a polytriazine imide structure. The transport mechanism involves a sequence of molecular orientation reversals directed by hydrogen-bonding interactions as the neutral molecules traverse the interlayer gap and pass through the intralayer voids that show similarities with the transport of water through transmembrane aquaporin channels in biological systems. The results suggest that nanoporous layered carbon nitrides can be useful for developing high-performance membranes.

Two-dimensional (2D) layered graphitic carbon nitride (gCN) nanosheets offer intriguing electronic and chemical properties.H owever,t he exfoliation and functionalisation of gCN for specific applications remain challenging.We report as calable one-pot reductive method to produce solutions of single-and few-layer 2D gCN nanosheets with excellent stability in ahigh mass yield (35 %) from polytriazine imide.High-resolution imaging confirmed the intact crystalline structure and identified an AB stacking for gCN layers.T he charge allows deliberate organic functionalisation of dissolved gCN,providing ag eneral route to adjust their properties.Graphitic carbon nitride (gCN) has triggered tremendous interest owing to its two-dimensional structure,w hich is analogous to that of graphene,b ut displays complementary characteristics. [1] In particular,ito ffers inherent semiconductivity with tuneable band gap and optical absorption, [2] whilst the different chemical valences of Nand Ccreate empty sites within the layers. [3] Monolayer/few-layer carbon nitride nanosheets (FL-CNs) have been isolated as an ew family of 2D layered materials,m otivated by their unique photocatalytic activity. [4] Several methods have been adopted to synthesize FL-CNs of various thicknesses/sizes. [5] Unfortunately,many of these processes damage the structure,altering the properties of interest;t hey are also time-consuming,p rovide low yields and dilute suspensions,a nd rely mostly on disordered heptazine-based gCNs.P olytriazine imide (PTI) has been previously synthesized and characterized by an umber of bottom-up approaches. [6] PTI is more crystalline than its heptazine-based counterpart, containing genuine planar layers of imide-bridged triazine units, [7] and its exfoliation into high-quality 2D FL-CN crystals is,t herefore,a ttractive. Achieving an on-damaging preparation of 2D few-layered PTI (FL-PTI) in high yield is still in its infancy, although slow dissolution has recently been reported as av iable method. [8] Moreover,w hile covalent functionalisation is av ital tool in tailoring the properties of nanomaterials, [9] to date,there has been little direct covalent functionalisation of PTI.Herein, we describe the simple,o ne-pot exfoliation, dissolution, and optional functionalisation of FL-PTI by reduction. Av ariety of routes have been developed for reductive charging of 2D nanomaterials in solution, including the use of Birch reductions,m etal amalgam, and organic single electron charge transfer agents (CTAs). [10] Theu se of sodium naphthalide (NaNp) dissolved in N,N-dimethylacetamide (DMAc) was recently found to be especially effective for the dissolution and functionalisation of single-wall nanotubes in as ingle step. [11] Here,t his method was adapted to gCNs,specifically PTIs.Successful exfoliation of PTI was achieved by aframework charging process (Figure 1). Sodium was used as the electron source to form naphthalide ions,w hich act as the CTA. DMAc is an excellent room-temperature solvent for naphthalene/naphthalide and anioni...

The spontaneous dissolution of 2D carbon nitrides with polytriazine imide (PTI) diverges dramatically from the inherent insolubility of other 2D materials such as graphene. The dissolution may be controlled to give tuneable photoluminescence.