Melamine Polymerization Promotes Compact Phosphorus/Carbon Composite for High-Performance and Safe Lithium Storage.

Phosphorus is regarded as a promising material for high-performance lithium-ion batteries (LIBs) due to its high theoretical capacity, appropriate lithiation potential, and low lithium-ion diffusion barrier. Phosphorus/carbon composites (PC) are engineered to serve as high-capacity high-rate anodes; the interaction between phosphorus and carbon, long-term capacity retention, and safety problems are important issues that must be well addressed simultaneously. Herein, an in situ polymerization approach to fabricate a poly-melamine-hybridized (pMA) phosphorus/carbon composite (pMA-PC) is employed. The pMA hybridization enhances the density and electrical conductivity of the PC, improves the structural integrity, and facilitates stable electron transfer within the pMA-PC composite. Moreover, the pMA-PC composite exhibits efficient adsorption of lithium polysulfides, enabling stable transport of Li+ ions. Therefore, the pMA-PC anode demonstrates a high specific charging capacity of 1,381 mAh g-1 at 10 A g-1, and a great capacity retention of 86.7% at 1 A g-1 over 500 cycles. The synergistic effect of phosphorus and nitrogen further confers excellent flame retardant properties to the pMA-PC anode, including self-extinguishing in 2.5 s, and a much lower combustion temperature than PC. The enhanced capacity and safety performance of pMA-PC show potential in future high-capacity and high-rate LIBs.

Enhanced Catalytic Activity of Crystalline Phosphorus Nanosheets Fabricated via Solvothermal Phase Transformation.

The newly reported crystalline phosphorus nanosheets (cryst-P NSs) exhibit promising features for industrial applications, including outstanding air-water stability and facile large-scale production. However, their complex crystallization impedes a priori tailoring. Herein, the temporal evolution of cryst-P NSs was investigated with the optimized synthesis parameters. The occurrence of self-assembly and solid-state rearrangement unveiled the existence of an intermediate phase as the bulk crystalline precursor and the predominance of nonclassical crystallization pathway(s). With the upgraded synthesis protocol simultaneously strengthening the merits of cryst-P NSs, their catalytic performances were evaluated in various electro- and/or photocatalytic reactions spanning hydrogen and oxygen evolution, full water splitting, CO2 reduction, and organic pollutant decomposition. Superior catalytic activities and orders of magnitude longer lifetimes were consistently discerned compared with the widely employed black phosphorus nanosheets with similar size and thickness. The exciting discoveries in both fundamental crystallization and catalytic applications drastically thrust the comprehension of elemental phosphorus, shedding light on the encouraging capabilities of solvothermal synthesis strategies in the design and systematic tailoring of phosphorus materials.

Renaissance of elemental phosphorus materials: properties, synthesis, and applications in sustainable energy and environment.

The polymorphism of phosphorus-based materials has garnered much research interest, and the variable chemical bonding structures give rise to a variety of micro and nanostructures. Among the different types of materials containing phosphorus, elemental phosphorus materials (EPMs) constitute the foundation for the synthesis of related compounds. EPMs are experiencing a renaissance in the post-graphene era, thanks to recent advancements in the scaling-down of black phosphorus, amorphous red phosphorus, violet phosphorus, and fibrous phosphorus and consequently, diverse classes of low-dimensional sheets, ribbons, and dots of EPMs with intriguing properties have been produced. The nanostructured EPMs featuring tunable bandgaps, moderate carrier mobility, and excellent optical absorption have shown great potential in energy conversion, energy storage, and environmental remediation. It is thus important to have a good understanding of the differences and interrelationships among diverse EPMs, their intrinsic physical and chemical properties, the synthesis of specific structures, and the selection of suitable nanostructures of EPMs for particular applications. In this comprehensive review, we aim to provide an in-depth analysis and discussion of the fundamental physicochemical properties, synthesis, and applications of EPMs in the areas of energy conversion, energy storage, and environmental remediation. Our evaluations are based on recent literature on well-established phosphorus allotropes and theoretical predictions of new EPMs. The objective of this review is to enhance our comprehension of the characteristics of EPMs, keep abreast of recent advances, and provide guidance for future research of EPMs in the fields of chemistry and materials science.

Black Phosphorus/Carbon Nanoframes for Efficient Flexible All-Solid-State Supercapacitor.

A flexible all-solid-state supercapacitor with fast charging speed and high power density is a promising high-performance energy storage and sensor device in photovoltaic systems. Two-dimensional black phosphorus (BP) is a prospective electrode nanomaterial, but it struggles to fully exert its properties limited by its self-stacking. Herein, by embedding carbon nanoparticles into the interlayer of BP microplates, the designed BP/carbon nanoframe (BP/C NF) forms a certain nano-gap on the substrate for promoting the orderly transport of charges. The corresponding supercapacitor BP/C SC has a capacity of 372 F g-1, which is higher than that constructed from BP microplates (32.6 F g-1). Moreover, the BP/C SC exhibits good stability with a ca. 90% of capacitance retentions after 10,000 repeated bending and long-term cycles. Thus, the proposed strategy of using BP/carbon nanoframes is feasible to develop exceptional flexible energy devices, and it can guide the design of relevant two-dimensional nanocomposites.

Size-dependent flame retardancy of black phosphorus nanosheets.

Two-dimensional black phosphorus (BP) nanosheets are potential flame-retardant nano-additives. Herein, the effects of the size of BP nanosheets embedded in epoxy resin (EP) on flame retardancy are studied. BP nanosheets with four different sizes are synthesized from bulk BP by different exfoliation methods including solid ball milling, liquid ball milling, ultrasonic liquid exfoliation, and electrochemical exfoliation (samples are designated as sb-BP, lb-BP, us-BP, and ec-BP, respectively). lb-BP exhibits the best dispersion in the EP matrix, and the lb-BP/EP composite shows the best flame-retardancy properties among the four BP/EP composites. Compared to bare EP, lb-BP/EP shows obvious improvements including the reduction in the heat release peak rate by 34.4%, total heat release by 27.0%, peak of smoke production rate by 69.2%, and total production of carbon monoxide by 50.8%. The mechanistic study reveals that lb-BP serves as a barrier and carbonization catalyst to delay combustion. These results confirm the size dependence of flame-retardancy properties of BP nanosheets and the new knowledge provides insights into the size dependent effects of other two-dimensional materials.

Copper(II)-ß-cyclodextrin and CuO functionalized graphene oxide composite for fast removal of thiophenic sulfides with high efficiency.

A novel copper(II)-ß-cyclodextrin and CuO functionalized graphene oxide composite (CD-CuO/NH2-GO) was successfully synthesized by reacting mono-6-O-toluenesulfonyl-copper(II)-ß-cyclodextrin with amino and CuO functionalized graphene oxide. The characterization results showed that the CD-CuO/NH2-GO was well-characterized and has a BET surface area of 746.5 m2 g-1 and good thermal stability, and CD and CuO were uniformly dispersed. The unique structure of CD-CuO/NH2-GO is conducive to the synergistic effect of the different components, especially for the inclusion ability of CD. Benefiting from that, CD-CuO/NH2-GO could quickly and efficiently remove the thiophenic sulfides, which are difficult to be economically removed by hydrodesulfurization. The removal efficiency for the three sulfides was in the order of benzothiophene > dibenzothiophene > thiophene. The desulfurization process of benzothiophene has the fastest desulfurization rate (0.121 g mg-1 min-1) and maximum sulfur capacity (12.75 mg S g-1). The different molecular inclusion ability of CD for the thiophenic sulfides demonstrates the difference in the desulfurization of CD-CuO/NH2-GO. The work highlights the synthesis and the potential application in fuel desulfurization of supramolecular GO composite nanomaterials.