Advances in poly(heptazine imide)/poly(triazine imide) photocatalyst

Polymeric carbon nitride(PCN)has garnered increasing attention as a metal-free photocatalyst with a suitable band gap.In efforts to enhance its photocatalytic performance,researchers have examined various PCN materials,including poly(heptazine imide)(PHI)and poly(triazine imide)(PTI),two isomers within the PCN family that exhibit distinct and superior photocatalytic activity compared to other forms.The challenge,however,lies in the common practice among researchers to categorize PHI and PTI along with other PCN types under the overarching term“g-C_(3)N_(4),”which significantly impedes optimization efforts.The objective of this review is to provide comprehensive insights into the structural features,photoelectrochemical properties,and effective characterization methods employed for distinguishing between PHI and PTI materials.The review also summarizes various optimization strategies,such as crystallinity adjustments,defect engineering,morphology control,constructing heterojunction,and atomic-level metal loading dispersion,to elevate the photocatalytic activity of PHI and PTI,in addition to summarizing the history of carbon nitride development.Furthermore,this review highlights the primary applications of PHI and PTI,encompassing nitrogen fixation,biomass conversion,organic synthesis,CO_(2)reduction,pollutant degradation,H_(2)O_(2)production,and photocatalytic water splitting.Lastly,the prospects and challenges associated with further advancing PHI and PTI are thoroughly examined.

MXene derivative Ta_(4)C_(3)-Ta_(2)O_(5) heterostructure as bi-functional barrier for Li-S batteries

The shuttle effect of polysulfides during the charging and discharging of lithium-sulfur(Li-S)batteries and the growth of Li dendrites are crucial obstacles to hinder the commercialization of Li-S batteries.Heterostructure engineering is an effective strategy to accelerate catalytic conversion and suppress the dissolution of polysulfides.Herein,we report a Ta_(4)C_(3)-Ta_(2)O_(5) heterostructure composite as a bi-functional modified separator that not only achieves effective protection for lithium metal but also accelerates the polysulfides redox kinetics process.This heterostructure possesses efficient chemical anchoring and abundant active sites to immobilize polysulfides by synergistic effect,which endows a stable long cycling performance for Li-S batteries.This corresponds to an initial high capacity of 801.9 mAh g^(–1) at 1 C with a decay rate of 0.086%for 500 cycles.Due to its high Young’s modulus(up to 384 GPa),Ta_(4)C_(3) contributes to forming a protective layer on the Li metal surface to inhibit the growth of Li dendrites.Accordingly,the symmetrical cell has a stable overpotential for 700 cycles at 20 mA cm^(–2)/20 mAh cm^(–2).So,this“one stone two birds”design affords a novel perspective for high-energy Li-S battery storage system design and Li metal protection.

Highly redispersible CNT dough for better processiblity

Carbon nanotubes(CNTs)have received considerable attention for their excellent thermal and electrical conductivity as well as scalable production.However,CNT dispersions are prone to settling and have a short shelf time,especially under high concentration,which significantly hinders their further processing and increases transportation costs.Here,we report a highly concentrated CNT dough enabled by ionic liquid crystal(ILC)as auxiliaries.Benefiting from the temperature-controlled physical transformation of the ILC,the CNTs of the powder state are successfully transferred to highly processable dough with excellent electrical conductivity,flame retardancy,and outstanding redispersibility even after 180 days of storage.In particular,the CNT dough exhibits excellent self-healing properties and good reshapable capability.Various bulk form CNT derived from the ILC armored CNT dough are realized by facile processing technique.Hybrid nanocomposite papers with ANF nanofiber exhibited excellent photothermal conversion and Joule heating properties.The redispersible CNT doughs presented here promise to revolutionize traditional CNT powder and dispersions as the primary raw material for building CNT-based architectures and facilitate the large-scale application of CNTs.

Growth of ultra-dense MoS_(2) nanosheets on carbon fibers to improve the mechanical and tribological properties of polyimide composites

To enhance the interface bonding of polyimide(PI)/carbon fiber(CF)composites,CFs were functionalized by introducing a polydopamine(PDA)transition layer,whose active groups provide absorption sites for the growth of molybdenum disulfide(MoS_(2))nanosheets and improve the bonding strength with PI.Uniform and dense MoS_(2) nanosheets with thicknesses of 30–40 nm on the surface of the PDA@CF were obtained via a subsequent hydrothermal method.As a result,the interface between the CF and the PI matrix becomes more compact with the help of the PDA transition layer and MoS_(2) nanosheets.This is beneficial in forming PI/CF–MoS_(2) composites with better thermal stability,higher tensile strength,and enhanced tribological properties.The lubricating and reinforcing effects of the hybrid CF–MoS_(2) in the PI composite are discussed in detail.The tensile strength of the PI/CF–MoS_(2) composite increases by 43%,and the friction coefficient and the wear rate reduce by 57%and 77%,respectively,compared to those of the pure PI.These values are higher than those of the PI/CF composites without MoS_(2) nanosheets.These results indicate that the CF–MoS_(2) hybrid material can be used as an additive to improve the mechanical and tribological properties of polymers.