Publications

The substitution of noble metal catalysts with earth abundant TMs as electrocatalysts for hydrogen production is of great significance. One biggest bottleneck for high-efficiency water electrolysis in TM catalysts is the sluggish reaction kinetics or electron transport efficiency. The electrical coupling between the substrate and the catalytic material can accelerate the electron transport, enhancing the charge transfer kinetics, and thereby improve the catalytic performance of the catalyst. Herein, we report a sandwich-structured CNF/Co3S4/MoS2, MoS2 grown in-situ on N-doped nanofibers with Co3S4 nanoparticles via electrospinning, carbonization and hydrothermal process, as self-supported electrodes for hydrogen evolution reaction. The sandwich structure is comprised of CNFs/Co3S4/MoS2 as substrate/accelerator/catalyst. Thereinto, the three-dimensional CNF framework, intrinsically doped by nitrogen, can open accessible channels for reactants and served as substrates for the in-situ growth of Co3S4 and MoS2 nanocrystals with high conductivity and massive active sites. Hence, the CNF/Co3S4/MoS2 shows outstanding catalytical performance in water electrospinning, only 80 mV required to drive 10 mA cm−2 current density with the Tafel slope of 99.2 mV dec−1 in alkaline media. Besides, the performance can be maintained for at least 40 h with negligible decline. This experiment can provide a new idea for the design of efficient and stable self-supporting electrodes.

A combination of malleability, supramechanical properties and multi-stimuli response into catalyst-free and commercially available polymer-based networks is particularly attractive to extend the realm of thermally malleable polymers. Toward this goal, herein we demonstrated a paradigm by introducing dynamic imine bonds into styrene-butadiene rubber (SBR)/graphene composites. SBR was firstly grafted with aldehyde groups and then cross-linked with p-phenylene diamine and it-modified graphene through imine condensation between aldehyde and amino groups. The crosslinked networks were able to alter their topologies via imine exchange reactions in both the bulk network and SBR-graphene interphase in the absence of catalyst, enabling them to be recycled and reshaped under heating or IR irradiation. The incorporation of graphene led to spectacular improvements on the mechanical properties of vitrimer composites, and the mechanical properties could be tuned through solid-state drawing. The relationships between morphological structure and dynamic properties as well as mechanical properties of the vitrimer composites were addressed.

ABSTRACT This study developed multifunctional fibrous membranes for wearable textiles. Using coaxial electrospinning, octadecane (Oct) was encapsulated within polylactic acid (PLA) to form core‐shell PLA@Oct (P 1 ) fibers for thermal regulation. MXene was then sprayed onto P 1 to create a conductive layer (P 1 M) for electromagnetic interference (EMI) shielding. Finally, a waterproof layer of PLA/polyvinylidene fluoride (PVDF) blended with fluorinated SiO 2 was electrospun atop P 1 M, resulting in the multilayer membrane P 1 MP 2 . The optimized membrane demonstrated a high latent heat of 111.73 J/g, an effective EMI shielding effectiveness of 32.68 dB in the X‐band, and a hydrophobic contact angle of 136.91°. This integration of temperature management, EMI shielding, and waterproof showcases certain potential for advanced wearable applications.

Constructing dynamic covalent bonds (DCBs) in rubbers provides a promising avenue to resolve the trade‐offs between chemical crosslinking and recyclability. The reinforcement of dynamic covalent networks by nanofilling is widely adopted, which, however, inevitably hinders the exchange reaction of DCBs and network rearrangement due to the restrictions on chain mobility imposed by fillers. To date, the reinforcement of dynamic covalent networks without affecting the dynamic properties remains challenging. In this work, we report a dual dynamic crosslinking strategy by engineering reversible noncovalent bonds into dynamic covalent rubbers to improve mechanical performance and simultaneously maintain desirable malleability and reprocessability. Specifically, dynamic boronic ester‐crosslinked styrene–butadiene rubber is firstly prepared and then modified through triazolinedione (TAD) click reaction. The grafted urazole groups can form hydrogen bond interactions that further aggregate to form clusters and phase‐separation structure in the networks. Due to the reversible nature of hydrogen bonds, they can act in a sacrificial manner to dissipate mechanical energy, leading to a combination of improved strength, modulus and toughness of the networks. More importantly, the hydrogen‐bonded clusters are dissociated at elevated temperatures, enabling the network dynamic properties to be largely preserved. In addition, the dynamic features of the dual crosslinks (hydrogen bonds and boronic esters) endow the TAD‐modified networks with reconfigurable shape memory effect. © 2023 Society of Industrial Chemistry.

Exploring efficient and economical electrocatalysts to replace noble metal electrocatalysts has become a major research focus nowadays. In this paper, Ru-doped Co nanoparticles loaded on carbon nanosheet (CNS) in-situ grown on carbon nanofibers (Ru–Co@CNS/CNFs) were constructed as a self-supporting working electrode for high-efficiency hydrogen evolution. The prepared Ru–Co@CNS/CNFs possessed excellent catalytic activity with only 78 mV overpotential at 10 mA cm−2 current density and good stability with only 102 mV voltage attenuation at 100 mA cm−2 current density for 100 h continuous operation. The excellent catalytic performance could be attributed to the unique microstructure of the nanosheets in-situ grown on the nanofibers, it resulted in a higher Co surface density of 1.28 mg cm−2, indicating more loading of metal to improve catalytic activity of HER, and the formed Ru-doped Co nanoparticles could be evenly distributed on the carbon nanosheets to prevent the aggregation of nanoparticles, which could expose more active sites. Additionally, the density functional theory (DFT) calculations revealed Ru doping could accelerate the dissociation of water, optimize the adsorption energy of hydrogen intermediates and improve the kinetics of the HER reaction. This work provides a new approach to reduce the use of noble metals while improving the catalytic performance of catalysts.

Silica is one of the most important reinforcements in the rubber industry due to its indispensable applications in green tires. However, the significant difference in polarity between conventional diene rubber and silica generally results in poor silica dispersion and, hence, considerably compromises the overall performance of the composites. Herein, a poly (hydroxyethyl methacrylate) oligomer was synthesized via living radical polymerization using disulfiram as an iniferter. Upon thermal activation, the oligomer can further divide into macroradicals that are capable of directly grafting onto the unsaturated moieties in the rubber skeleton. Therefore, the pendant ester and hydroxyl functionalities can interact with silanol groups on the silica surface through interfacial hydrogen bonding, which significantly improves the interfacial interaction and facilitates the dispersion of silica. Accordingly, incorporating a small amount of oligomer (less than 3.5 wt%) can achieve a remarkable improvement in the tensile modulus and rolling and wet skid resistances of the obtained composites. We envisage that the present reactive oligomer can provide an effective strategy toward in situ modification of the rubber skeleton, which also has significant potential to optimize the static and dynamic performance of rubber/silica composites for tire tread applications.

In polymer composites, filler dispersion and interfacial adhesion are two critical factors in determining their properties. To date, it still remains a challenge to achieve uniform filler dispersion and implement interfacial tailoring in rubber composites by direct melt mixing. In this study, we prepared graphene oxide (GO) slurry in acetone via a simple solvent exchange method and modified GO in the slurry. Then the slurry was compounded with nitrile rubber on two-roll mill to produce composites. Morphological and interfacial structural studies revealed that GO was dispersed at nano-scale in the composites, and the dispersion of GO and interfacial adhesion were further improved upon the modification of GO with silane. Consequently, the mechanical properties of the composites were remarkably enhanced by adding GO.

No abstract is provided for this article.

Covalently cross-linked rubbers are indispensable in many important fields due to their unique entropic elasticity. For rubbers cross-linking, the addition of toxic curing agents, release of toxic volatile organic compounds (VOCs), and recycling of waste rubber are three important issues. A combination of green curing chemistry and efficient recycling into commercial polyolefin rubbers is of great importance. Herein, we demonstrate a facile and promising way to incorporate dynamic covalent bonds into ethylene-propylene-diene monomer (EPDM)/carbon black (CB) composites. The epoxy-functionalized EPDM (e-EPDM) was prepared using an in situ epoxidation reaction and then cured with biobased decanedioicacid (DA) through the reactions between the epoxy groups in e-EPDM and the carboxylic groups in DA. Because of the existence of exchangeable β-hydroxyl ester, the covalently cross-linked networks in e-EPDM/CB composites were able to rearrange their topological structure at high temperature, endowing the composites with recycled and reshaped abilities. More importantly, the recycled e-EPDM/CB composites still exhibit outstanding mechanical properties which can meet the needs of practical applications. This strategy may provide an efficient, green, and sustainable way to address the problems brought from rubbers cross-linking.

The problems of high volatile organic compound (VOC) emission and low efficiency of silane coupling agents (SCAs) used in the rubber/silica composites for "green tires" have been troubling the rubber industry. A unique silane (MFSi) integrating hydroxyls, tertiary nitrogen, and norbornenyl were prepared by a solvent-free/catalyst-free one-pot method. MFSi can graft onto the rubber chain through a highly efficient norbornenyl/sulfur reaction, while the dangling hydroxyls in MFSi can improve its affinity with silica and tertiary nitrogen has a significant internal catalytic effect on the silanization of silica. As a result, MFSi shows a significantly higher coupling efficiency of silica-filled composites compared to the most widely used SCAs. Consequently, MFSi-modified composites exhibit excellent environmental friendliness, including significantly reduced heat buildup (∼55%) and abrasion loss (∼53%) and VOC emissions (∼42%). We envision that the design of the multifunctional mediator will provide valuable insights into the development of high-performance "green tires" in a more environmentally friendly manner.

The functionalized graphene (JTPG) is fabricated by chemical conversion of graphene oxide (GO), using tea polyphenols (TP) as the reducer and stabilizer, followed by further derivatization through the Mannich reaction between the pyrogallol groups on TP and Jeffamine M-2070. JTPG exhibits solubility in a broad spectrum of solvents, long-term stability and single-layered dispersion in water and organic solvents, which are substantiated by AFM, TEM, and XRD. The paper-like JTPG hybrids prepared by vacuum-assisted filtration exhibits an unusual combination of high toughness (tensile strength of ~275 MPa and break strain of ~8%) and high electrical conductivity (~700 S/m). Still, JTPG is revealed to be very promising in the fabrication of polymer/graphene composites due to the excellent solubility in the solvent with low boiling point and low toxicity. Accordingly, as an example, nitrile rubber/JTPG composites are fabricated by the solution compounding in acetone. The resulted composite shows low threshold percolation at 0.23 vol.% of graphene. The versatilities both in dispersibility and performance, together with the scalable process of JTPG, enable a new way to scale up the fabrication of the graphene-based polymer composites or hybrids with high performance.

A new route for liquefying graphene oxide (GO) into supramolecular ionic liquid (SIL) was proposed by the grafting of chloroacetic acid and the subsequent neutralization of carboxy groups with monofunctionalized polyetheramine (Jeffamine 2070). The rheological measurements verified its viscoelastic and liquid-like behavior. The peculiar phenomenon was mainly attributed to the formation of ionic bonds between the corona of chloroacetic acid and the canopy of Jeffamine. This type of highly viscous GO-based liquid possesses excellent amphiphilicity.

Boron nitride nanosheets (BNNSs) have captured much attention in the fabrication of thermally conductive and electrically insulating polymer-based composites. However, inert surface chemistry of BNNSs largely hampers their applications in polymer composites. Herein, we report a facile approach for the fabrication of elastomer/BNNSs composites with high thermal conductivity. BNNSs were first wrapped by polyrhodanine in water to form the polyrhodanine@BNNSs nanostructure (PRh-BNNSs) and then compounded with styrene-butadiene rubber to form the elastomer composites. Due to the unique curing reactivity of polyrhodanine, strong interfaces were formed in the resulting elastomer composites. Accordingly, the SBR/PRh-BNNSs composites exhibited unique combination of high mechanical properties and high thermal conductivity. Importantly, the orientation of BNNSs in the elastomer led to further increase in thermal conductivity. Overall, the present work offers a new route for the design of thermally conductive elastomers through the combination of efficient interfacial modification and filler organization.

The fascinating properties of carbon nanotubes (CNTs) make them highly promising in fabricating polymer composites. Yet, the property enhancements of polymer/CNTs composites remain far behind the theoretical predictions. A critical issue to resolve this dilemma is to align CNTs in polymer matrices. Thus far, the state of art approaches to create CNT alignment either require complicated preparation processes and specific apparatuses, or is limited to thermoplastic polymers. Here, inspired by the network rearrangement ability of vitrimer in the solid state, we bring forth a facile methodology to align CNT in covalently cross-linked polymers by uniaxially stretching dynamic. Specifically, dynamic boronic ester bond-cross-linked epoxidized natural rubber/CNTs vitrimer composites with randomly dispersed CNTs are prepared, which are able to rearrange the network topologies and release stress at elevated temperatures through boronic ester transesterifications. The alignment of CNTs is performed by the uniaxial stretching of the composites and subsequent cross-link reshuffling at elevated temperatures, which results in anisotropic composites with remarkably enhanced mechanical properties and reduced electrical conductivity along the stretching direction. Furthermore, the mechanical properties of the composites can be readily adjusted by changing the applied strain, relaxation time and temperature due to the modulated CNT alignment degree. With this example, we envisage that this work offers a conceptual and facile approach to align anisotropic fillers in covalently cross-linked polymers.

Methacrylic acid (MAA) is investigated as a novel in situ interfacial modifier for styrene-butadiene rubber (SBR)/boehmite (BM) composite via a direct blending method. The reaction mechanism for the modification was revealed to be the BM/MAA coordination and MAA/rubber grafting reaction. The substantiated BM/MAA coordination can improve the dispersion of BM in rubber matrix. It is illustrated that the ultimate mechanical performance and interfacial interaction are significantly enhanced by the in situ modification. The strong interaction between BM and SBR and the improved dispersion of BM in the rubber matrix are responsible for the largely enhanced mechanical properties.