Topological Defect-Regulated Porous Carbon Anodes with Fast Interfacial and Bulk Kinetics for High-Rate and High-Energy-Density Potassium-Ion Batteries.

Carbonaceous materials are regarded as one of the most promising anodes for potassium-ion batteries (PIBs), but their rate capabilities are largely limited by the slow solid-state potassium diffusion kinetics inside anode and sluggish interfacial potassium ion transfer process. Herein, high-rate and high-capacity PIBs are demonstrated by facile topological defect-regulation of the microstructure of carbon anodes. The carbon lattice of the as-obtained porous carbon nanosheets (CNSs) with abundant topological defects (TDPCNSs) holds relatively high potassium adsorption energy yet low potassium migration barrier, thereby enabling efficient storage and diffusion of potassium inside graphitic layers. Moreover, the topological defects can induce preferential decomposition of anions, leading to the formation of high potassium ion conductive solid electrolyte interphase (SEI) film with decreased potassium ion de-solvation and transfer barrier. Additionally, the dominant sp2-hybridized carbon conjugated skeleton of TDPCNSs enables high electrical conductivity (39.4 S cm-1) and relatively low potassium storage potential. As a result, the as-constructed TDPCNSs anode demonstrates high potassium storage capacity (504 mA h g-1 at 0.1 A g-1), remarkable rate capability (118 mA h g-1 at 40 A g-1), as well as long-term cycling stability.

Pseudocapacitive Potassium-Ion Intercalation Enabled by Topologically Defective Soft Carbon toward High-Rate, Large-Areal-Capacity, and Low-Temperature Potassium-Ion Batteries.

Carbonaceous materials are widely investigated as anodes for potassium-ion batteries (PIBs). However, the inferior rate capability, low areal capacity, and limited working temperature caused by sluggish K-ions diffusion kinetics are still primary challenges for carbon-based anodes. Herein, a simple temperature-programmed co-pyrolysis strategy is proposed for the efficient synthesis of topologically defective soft carbon (TDSC) based on inexpensive pitch and melamine. The skeletons of TDSC are optimized with shortened graphite-like microcrystals, enlarged interlayer spacing, and abundant topological defects (e.g., pentagons, heptagons, and octagons), which endow TDSC with fast pseudocapacitive K-ion intercalation behavior. Meanwhile, micrometer-sized structure can reduce the electrolyte degradation over particle surface and avoid unnecessary voids, ensuring a high initial Coulombic efficiency as well as high energy density. These synergistic structural advantages contribute to excellent rate capability (116 mA h g-1 at 20 C), impressive areal capacity (1.83 mA h cm-2 with a mass loading of 8.32 mg cm-2 ), long-term cycling stability (capacity retention of 91.8% after 1200 h cycling), and low working temperature (-10 °C) of TDSC anodes, demonstrating great potential for the practical application of PIBs.

Facile and Universal Defect Engineering Toward Highly Stable Carbon-Based Polymer Brushes with High Grafting Density.

Carbon-based polymer brushes (CBPBs) are an important class of functional polymer materials, which synergistically combine the advantageous properties of both carbons and polymers. However, the conventional fabrication procedures of CBPBs involve tedious multistep modification, including preoxidation of carbon substrates, introduction of initiating groups, and subsequent graft polymerization. In this study, a simple yet versatile defect-engineering strategy is proposed for the efficient synthesis of high-grafting-density CBPBs with highly stable CC linkages via free radical polymerization. This strategy involves the introduction and removal of nitrogen heteroatoms in the carbon skeletons via a simple temperature-Fmed heat treatment, leading to the formation of numerous carbon defects (e.g., pentagons, heptagons, and octagons) with reactive C=C bonds in the carbon substrates. The as-proposed methodology enables the facile fabrication of CBPBs with various carbon substrates and polymers. More importantly, the highly grafted polymer chains in the resulting CBPBs are tethered with the carbon skeletons by robust CC bonds, which can endure strong acid and alkali environments. These interesting findings will shed new light on the well-orchestrated design of CBPBs and broaden their applications in various areas with fascinating performances.

A robust all-organic protective layer towards ultrahigh-rate and large-capacity Li metal anodes.

The low cycling efficiency and uncontrolled dendrite growth resulting from an unstable and heterogeneous lithium-electrolyte interface have largely hindered the practical application of lithium metal batteries. In this study, a robust all-organic interfacial protective layer has been developed to achieve a highly efficient and dendrite-free lithium metal anode by the rational integration of porous polymer-based molecular brushes (poly(oligo(ethylene glycol) methyl ether methacrylate)-grafted, hypercrosslinked poly(4-chloromethylstyrene) nanospheres, denoted as xPCMS-g-PEGMA) with single-ion-conductive lithiated Nafion. The porous xPCMS inner cores with rigid hypercrosslinked skeletons substantially increase mechanical robustness and provide adequate channels for rapid ionic conduction, while the flexible PEGMA and lithiated Nafion polymers enable the formation of a structurally stable artificial protective layer with uniform Li+ diffusion and high Li+ transference number. With such artificial solid electrolyte interphases, ultralong-term stable cycling at an ultrahigh current density of 10 mA cm-2 for over 9,100 h (>1 year) and unprecedented reversible lithium plating/stripping (over 2,800 h) at a large areal capacity (10 mAh cm-2) have been achieved for lithium metal anodes. Moreover, the protected anodes also show excellent cell stability when paired with high-loading cathodes (~4 mAh cm-2), demonstrating great prospects for the practical application of lithium metal batteries.

Molecular Engineering toward High-Crystallinity Yet High-Surface-Area Porous Carbon Nanosheets for Enhanced Electrocatalytic Oxygen Reduction.

Carbon-based nanomaterials have been regarded as promising non-noble metal catalysts for renewable energy conversion system (e.g., fuel cells and metal-air batteries). In general, graphitic skeleton and porous structure are both critical for the performances of carbon-based catalysts. However, the pursuit of high surface area while maintaining high graphitization degree remains an arduous challenge because of the trade-off relationship between these two key characteristics. Herein, a simple yet efficient approach is demonstrated to fabricate a class of 2D N-doped graphitized porous carbon nanosheets (GPCNSs) featuring both high crystallinity and high specific surface area by utilizing amine aromatic organoalkoxysilane as an all-in-one precursor and FeCl3 ·6H2 O as an active salt template. The highly porous structure of the as-obtained GPCNSs is mainly attributed to the alkoxysilane-derived SiOx nanodomains that function as micro/mesopore templates; meanwhile, the highly crystalline graphitic skeleton is synergistically contributed by the aromatic nucleus of the precursor and FeCl3 ·6H2 O. The unusual integration of graphitic skeleton with porous structure endows GPCNSs with superior catalytic activity and long-term stability when used as electrocatalysts for oxygen reduction reaction and Zn-air batteries. These findings will shed new light on the facile fabrication of highly porous carbon materials with desired graphitic structure for numerous applications.

Molecular Level Design of Nitrogen-Doped Well-Defined Microporous Carbon Spheres for Selective Adsorption and Electrocatalysis.

Nitrogen-doped porous carbon spheres have attracted great interest in diversified fields owing to their unique physical and chemical properties. However, the synthesis of nitrogen-doped porous carbon spheres with hierarchical superstructures and refined micropore structures is still a challenge. Herein, we develop a molecular-scale silica templating strategy to prepare nitrogen-doped microporous carbon spheres (MCSSs) with high porosity and a well-defined micropore structure. Octa(aminophenyl) polyhedral oligomeric silsesquioxane is used as a building block in MCSS precursors to provide precise molecular-scale templating and nitrogen doping. The morphology of MCSSs can be easily tuned by choosing the proper solvent. The as-synthesized MCSS with a large surface area (2036 m2 g-1), narrow micropore size distribution, nitrogen doping, and hierarchical geometry can serve as an efficient selective adsorbent for CO2 and organic pollutants. Furthermore, the MCSS decorated with Fe-N-C active sites (MCSS-Fe) shows enhanced electrocatalytic ORR activity in alkaline solution. This novel approach may open a new avenue for controllable fabrication of porous carbon spheres with desired geometry and well-designed pore structure and show potential applications in selective adsorption and catalysis.

A versatile sea anemone-inspired strategy toward 2D hybrid porous carbons from functional molecular brushes.

A generalized and facile strategy toward 2D hybrid porous carbons (2DHPCs) with various highly active functional species (e.g. Co, B, and P) is developed via 2D molecular brushes as biomimetic building blocks. The resulting 2DHPCs present superior electrochemical energy conversion and storage properties.

Template-Free Preparation of Hierarchical Porous Carbon Nanosheets for Lithium-Sulfur Battery.

Porous carbon nanosheets have the advantages of longitudinal continuity, transverse ultrathin, high specific surface area, and surface atomic activity, as well as the synergistic effect of micro and nanoproperties, so the research on their preparation, structure, and properties has attracted wide attention. A series of ultrathin hierarchical porous carbon nanosheets (HPCNs) is fabricated through carbonization of precursors obtained through the Friedel-Crafts reaction-assisted loading of polystyrene on graphene oxide. Hierarchical pore structures consist of three parts: (1) the micropores (1.3 nm), which were provided by porous polystyrene through the Friedel-Crafts reaction; (2) the mesopores (3.8 nm), which were provided by slab pores from the stack of carbon nanosheets; and (3) the pores (>5 nm) formed from the random stack of carbon nanosheets. Controlling the carbonization time and temperature adds to a prominent increase in specific surface area from 405.8 to 1420 m2 g-1. It was found that excessive carbonization would destroy the hierarchical pore structure. These porous carbon materials were used as cathode materials for lithium-sulfur battery and showed good performance. HPCN/sulfur cathode has good rate performance and cycle performance, and the capacity retention rate is 87% after the current density rises from 1 to 3 C and 91% after 200 cycles.

FeS/FeNC decorated N,S-co-doped porous carbon for enhanced ORR activity in alkaline media.

A novel strategy is developed to produce an FeS-FeNC-decorated hierarchical porous N,S-co-doped carbon (FeS-FeNC@NSC) electrocatalyst via introducing volatile FeCl3 into a porphyrin polymer framework followed by carbonization. The synergistic effect between the FeS nanoparticles and FeNC active sites in FeS-FeNC@NSC is beneficial for enhancing the ORR activity.

A new supramolecular binder strongly enhancing the electrochemistry performance for lithium-sulfur batteries.

As one of the indispensable components in lithium-sulfur batteries, the binders greatly impact battery performance. Herein, we report a new multifunctional supramolecular eutectic liquid (SEL) binder, consisting of diphenylamine (DP) and benzophenone (BP), which enables a strongly improved conductive network and anchored polysulfides for high-performance lithium-sulfur batteries. Compared with the traditional polyvinylidene fluoride (PVDF) binder, the SEL binder demonstrates remarkable improvement in both the mechanical performance and the capacity retention (83% over 200 cycles at 1C).

A versatile bottom-up interface self-assembly strategy to hairy nanoparticle-based 2D monolayered composite and functional nanosheets.

Herein, we present a universal bottom-up interface self-assembly of hairy nanoparticle strategy for 2D monolayered composite and functional nanosheets, including polymeric composite nanosheets and functional porous polymer and carbon nanosheets. By using diverse hairy nanoparticles as building blocks, a series of 2D monolayered polymeric composite nanosheets was prepared, demonstrating the universality of our strategy. Furthermore, the 2D polymeric composites could be easily transformed into 2D monolayered functional porous polymer and carbon nanosheets. We hope that this strategy will open a new door for the design and fabrication of advanced 2D composite and functional nanosheets and thus provide new opportunities for different fields including the environment, energy, catalysis and medicine.

3D porous carbon networks with highly dispersed SiOx by molecular-scale engineering toward stable lithium metal anodes.

3D porous carbon networks with highly dispersed SiOx have been successfully prepared by molecular-scale engineering with 1D molecular-brush precursors. Benefiting from the high-porosity interconnected structure and the lithiophilic SiOx nanodomains, the as-obtained composites show great advantages as 3D hosts to achieve stable Li plating/stripping.

Fabrication of Porous Nanonetwork-Structured Carbons from Well-Defined Cylindrical Molecular Bottlebrushes.

Atom transfer radical polymerization was utilized to prepare well-defined cylindrical molecular bottlebrushes which were employed as building blocks and transformed into porous nanonetwork-structured carbons (PNSCs) via hypercross-linking chemistry and shape-regulated carbonization. The as-prepared PNSCs exhibited a unique nanomorphology-tunable characteristic by simply varying carbonization conditions. Because of their three-dimensional network nanomorphologies with well-developed hierarchical porous structures and conductive carbon framework, the PNSCs demonstrated excellent electrochemical performance in lithium-sulfur batteries.

Two-dimensional molecular brush-functionalized porous bilayer composite separators toward ultrastable high-current density lithium metal anodes.

Lithium metal batteries have been considerably limited by the problems of uncontrolled dendritic lithium formation and the highly reactive nature of lithium with electrolytes. Herein, we have developed functional porous bilayer composite separators by simply blade-coating polyacrylamide-grafted graphene oxide molecular brushes onto commercial polypropylene separators. Our functional porous bilayer composite separators integrate the lithiophilic feature of hairy polyacrylamide chains and fast electrolyte diffusion pathways with the excellent mechanical strength of graphene oxide nanosheets and thus enable molecular-level homogeneous and fast lithium ionic flux on the surfaces of electrodes. As a result, dendrite-free uniform lithium deposition with a high Coulombic efficiency (98%) and ultralong-term reversible lithium plating/stripping (over 2600 h) at a high current density (2 mA cm-2) are achieved for lithium metal anodes. Remarkably, lithium metal anodes with an unprecedented stability of more than 1900 h cycling at an ultrahigh current density of 20 mA cm-2 are demonstrated.

All-in-One Porous Polymer Adsorbents with Excellent Environmental Chemosensory Responsivity, Visual Detectivity, Superfast Adsorption, and Easy Regeneration.

It remains a formidable challenge to construct advanced adsorbents with superb adsorption, environmental stimuli response, and real-time detection capability for efficiently treating contaminants from complex environmental systems. A novel class of an all-in-one microporous adsorbent that simultaneously has excellent environmental chemosensory responsivity, visual detectivity, superfast micropollutant adsorption, as well as easy regeneration is reported herein. The advanced microporous adsorbent discussed in this study presents a hairy nanospherical morphology composed of a hairy stimuli-responsive polymeric shell and a shell-assisted superadsorptive microporous core. The adsorbent not only exhibits a valuable capability of pollutant detection by visible fluorescence quenching, but can also remove organic micropollutants from polluted water with super-rapid speed (79%, 98%, and 100% of its equilibrium uptake in 7 s, 10 s, and 2 min, respectively) and excellent recyclability (>96%). More importantly, the adsorbent still shows unimpeded adsorption performance in the flow-through adsorption tests (15 mL min-1 ), indicating a very appealing application prospect.

Construction of 3D carbon networks with well-dispersed SiO x nanodomains from gelable building blocks for lithium-ion batteries.

Nonstoichiometric silicon oxide (SiO x ) with high theoretical capacity is a promising anode material for lithium-ion batteries (LIBs). However, volume changes and poor electronic conductivity of SiO x are major impediments to its practical application. The modification of SiO x with carbonaceous materials to accommodate volume variations and improve conductivity is a valuable strategy. Nanonetwork-structured (NNS) carbons have been paid great attention because of their unique three-dimensional structure, and high electronic and ionic conductivity. Incorporating SiO x with well-designed NNS carbons is a promising method to prepare high quality electrode materials for lithium-ion batteries. In this work, a fabrication approach is developed to synthesize a 3D carbon network composed of carbonaceous hybrid nanotubes with well-dispersed SiO x nanodomains (CNT@SiO x -C) from 1D gelable bottlebrushes as network building blocks based on molecular-scale interface engineering technology. Herein, nano-sized SiO x particles are embedded into the carbonaceous matrix to prevent their volume change during cycling. The experimental results indicated that the CNT@SiO x -C presents high reversible capacity, remarkable cycle life and high rate capability due to the high dispersion of nano-sized SiO x and conductive 3D carbon nanonetwork.

Porous Polymers as Multifunctional Material Platforms toward Task-Specific Applications.

Exploring advanced porous materials is of critical importance in the development of science and technology. Porous polymers, being famous for their all-organic components, tailored pore structures, and adjustable chemical components, have attracted an increasing level of research interest in a large number of applications, including gas adsorption/storage, separation, catalysis, environmental remediation, energy, optoelectronics, and health. Recent years have witnessed tremendous research breakthroughs in these fields thanks to the unique pore structures and versatile skeletons of porous polymers. Here, recent milestones in the diverse applications of porous polymers are presented, with an emphasis on the structural requirements or parameters that dominate their properties and functionalities. The Review covers the following applications: i) gas adsorption, ii) water treatment, iii) separation, iv) heterogeneous catalysis, v) electrochemical energy storage, vi) precursors for porous carbons, and vii) other applications (e.g., intelligent temperature control textiles, sensing, proton conduction, biomedicine, optoelectronics, and actuators). The key requirements for each application are discussed and an in-depth understanding of the structure-property relationships of these advanced materials is provided. Finally, a perspective on the future research directions and challenges in this field is presented for further studies.

Activation-free fabrication of high-surface-area porous carbon nanosheets from conjugated copolymers.

High-surface-area porous carbon nanosheets have been successfully prepared by direct carbonization of graphene oxide sandwiched poly(aniline-co-pyrrole). Benefiting from the distinct structure features of the poly(aniline-co-pyrrole) and its homogeneous deposition on the graphene oxide surface, the surface area of the porous carbon nanosheets is as high as 1606 m2 g-1.

A stepwise crosslinking strategy toward lamellar carbon frameworks with covalently connected alternate layers of porous carbon nanosheets and porous carbon spacers.

Lamellar carbon frameworks with covalently connected alternate layers of porous carbon nanosheets (PCNs) and porous carbon spacers (PCSs) were successfully fabricated based on the stepwise crosslinking of self-assembled lamellar block copolymers. The intrinsic porous structure of PCSs can maximize the utilization of well-developed surfaces/interfaces of the PCNs.

Construction of functional nanonetwork-structured carbon nitride with Au nanoparticle yolks for highly efficient photocatalytic applications.

We report a novel and versatile fabrication strategy for functional nanonetwork-structured carbon nitride with Au nanoparticle yolks (FNNS-C3N4-Au) based on hairy poly(acrylic acid)-grafted SiO2 nanospheres (Au@SiO2-g-PAA). Benefiting from the three-dimensional nanonetwork structure and well-distributed Au nanoparticles, the as-prepared nanocomposites demonstrated excellent photocatalysis performances (degradation rate constant: 1.8 × 10-2 min-1).