Heteroatom-doped carbon materials (HDCMs) have been widely studied as some of the most prominent material candidates for use in a wide range of applications, such as batteries, supercapacitors (SCs), and the oxygen reduction reaction (ORR) Over the past few years, various metal-free heteroatom-doped carbon composites have been developed via integrating different heteroatoms into carbon with different nanostructures, from single-atom doping (N, P, B, S, etc) to multiple heteroatom doping (N/P/S, N/S/B, etc) For the first time, this review comprehensively analyzes the relevant features of HDCMs used in batteries, SCs, and the ORR, and provides guidance for the design of more efficient materials By controlling the content and types of heteroatom-containing reagents, not only the physical and chemical properties of the material can be adjusted, but also the specific surface area and pore volume can be increased via controlling the morphology, thereby enhancing the electrochemical performance of the material Subsequently, this review summarizes the developments and the history of HDCMs, including synthesis methods, the relationship between doping (doping position and content) and performance, reaction mechanisms, and evaluations of systems In addition, the important role of oxygen doping is raised and discussed, to remind researchers not to ignore the role of oxygen in improving material properties Finally, future developments and challenges relating to key technologies in this thriving field are also discussed in this report

Untangling Respective Effects of Heteroatom-doped Carbon Materials in Batteries, Supercapacitors and ORR to Design High-Performance Materials

Lithium-ion batteries with routine carbonate electrolytes cannot exhibit satisfactory fast-charging performance and lithium plating is widely observed at low temperatures. Herein we demonstrate that a localized high-concentration electrolyte consisting of 1.5 M lithium bis(fluorosulfonyl)imide in dimethoxyethane with bis(2,2,2-trifluoroethyl) ether as the diluent, enables fast-charging of working batteries. A uniform and robust solid electrolyte interphase (SEI) can be achieved on graphite surface through the preferential decomposition of anions. The established SEI can significantly inhibit ether solvent co-intercalation into graphite and achieve highly reversible Li+ intercalation/de-intercalation. The graphite | Li cells exhibit fast-charging potential (340 mAh g-1 at 0.2 C and 220 mAh g-1 at 4 C), excellent cycling stability (ca. 85.5 % initial capacity retention for 200 cycles at 4 C), and impressive low-temperature performance.

Inhibiting Solvent Co-Intercalation in a Graphite Anode by a Localized High-Concentration Electrolyte in Fast-Charging Batteries

Enhanced Kinetics Harvested in Heteroatom Dual‐Doped Graphitic Hollow Architectures toward High Rate Printable Potassium‐Ion Batteries

Graphene is a 2D sheet of sp2 bonded carbon atoms and tends to aggregate together, due to the strong π-π stacking and van der Waals attraction between different layers. Its unique properties such as a high specific surface area and a fast mass transport rate are severely blocked. To address these issues, various kinds of 2D holey graphene and 3D porous graphene are either self-assembled from graphene layers or fabricated using graphene related materials such as graphene oxide and reduced graphene oxide. Porous graphene not only possesses unique pore structures, but also introduces abundant exposed edges and accelerates mass transfer. The properties and applications of these porous graphenes and their composites/hybrids have been extensively studied in recent years. Herein, recent progress and achievements in synthesis and functionalization of various 2D holey graphene and 3D porous graphene are reviewed. Of special interest, electrochemical applications of porous graphene and its hybrids in the fields of electrochemical sensing, electrocatalysis, and electrochemical energy storage, are highlighted. As the closing remarks, the challenges and opportunities for the future research of porous graphene and its composites are discussed and outlined.

https://onlinelibrary.wiley.com/doi/epdf/10.1002/smll.201903780

Recent Advances of Porous Graphene: Synthesis, Functionalization, and Electrochemical Applications.

The strategies concerning modification of the complex immune pathological inflammatory environment during acute spinal cord injury remain oversimplified and superficial. Inspired by the acidic microenvironment at acute injury sites, a functional pH-responsive immunoregulation-assisted neural regeneration strategy was constructed. With the capability of directly responding to the acidic microenvironment at focal areas followed by triggered release of the IL-4 plasmid-loaded liposomes within a few hours to suppress the release of inflammatory cytokines and promote neural differentiation of mesenchymal stem cells in vitro, the microenvironment-responsive immunoregulatory electrospun fibers were implanted into acute spinal cord injury rats. Together with sustained release of nerve growth factor (NGF) achieved by microsol core-shell structure, the immunological fiber scaffolds were revealed to bring significantly shifted immune cells subtype to down-regulate the acute inflammation response, reduce scar tissue formation, promote angiogenesis as well as neural differentiation at the injury site, and enhance functional recovery in vivo. Overall, this strategy provided a delivery system through microenvironment-responsive immunological regulation effect so as to break through the current dilemma from the contradiction between immune response and nerve regeneration, providing an alternative for the treatment of acute spinal cord injury. Inflammatory responses determine the pathological course of spinal cord injury. Here, the authors report on pH responsive fibers for triggered release of IL-4 plasmid liposomes and sustained release of nerve growth factor to regulate the immune response and promote nerve regeneration to enhance functional recovery.

/pdf/microenvironment-responsive-immunoregulatory-electrospun-35amw255ca.pdf

Microenvironment-responsive immunoregulatory electrospun fibers for promoting nerve function recovery

The application of graphene for electrochemical energy storage has received tremendous attention; however, challenges remain in synthesis and other aspects. Here we report the synthesis of high-quality, nitrogen-doped, mesoporous graphene particles through chemical vapor deposition with magnesium-oxide particles as the catalyst and template. Such particles possess excellent structural and electrochemical stability, electronic and ionic conductivity, enabling their use as high-performance anodes with high reversible capacity, outstanding rate performance (e.g., 1,138 mA h g-1 at 0.2 C or 440 mA h g-1 at 60 C with a mass loading of 1 mg cm-2), and excellent cycling stability (e.g., >99% capacity retention for 500 cycles at 2 C with a mass loading of 1 mg cm-2). Interestingly, thick electrodes could be fabricated with high areal capacity and current density (e.g., 6.1 mA h cm-2 at 0.9 mA cm-2), providing an intriguing class of materials for lithium-ion batteries with high energy and power performance.

/pdf/high-quality-mesoporous-graphene-particles-as-high-energy-4bwqpwxkz0.pdf

High-quality mesoporous graphene particles as high-energy and fast-charging anodes for lithium-ion batteries

The central nervous system (CNS) plays a central role in the control of sensory and motor functions, and the disruption of its barriers can result in severe and debilitating neurological disorders. Neurotrophins are promising therapeutic agents for neural regeneration in the damaged CNS. However, their penetration across the blood-brain barrier remains a formidable challenge, representing a bottleneck for brain and spinal cord therapy. Herein, a nanocapsule-based delivery system is reported that enables intravenously injected nerve growth factor (NGF) to enter the CNS in healthy mice and nonhuman primates. Under pathological conditions, the delivery of NGF enables neural regeneration, tissue remodeling, and functional recovery in mice with spinal cord injury. This technology can be utilized to deliver other neurotrophins and growth factors to the CNS, opening a new avenue for tissue engineering and the treatment of CNS disorders and neurodegenerative diseases.

Efficient Delivery of Nerve Growth Factors to the Central Nervous System for Neural Regeneration

https://onlinelibrary.wiley.com/doi/epdf/10.1002/adma.201970233

Bin Xu

Papers

High-quality mesoporous graphene particles as high-energy and fast-charging anodes for lithium-ion batteries

Efficient Delivery of Nerve Growth Factors to the Central Nervous System for Neural Regeneration

Neural Regeneration: Efficient Delivery of Nerve Growth Factors to the Central Nervous System for Neural Regeneration (Adv. Mater. 33/2019)