Bipyridine Modified Conjugated Carbon Aerogels as a Platform for the Electrocatalysis of Oxygen Reduction Reaction

Aerogels offer a great platform for heterogeneous electrocatalysis owing to their high surface area and porosity. Atomically dispersed transition metal ions can be imbedded in these platforms at ultra-high site density to make them catalytically active for various reactions. Herein, the synthesis of a new class of conjugated microporous organic aerogels that are used as covalent 3D frameworks for the electrocatalysis of oxygen reduction reaction (ORR) is reported. Modified aerogels functionalized with bipyridine ligands enable copper ion complexation in a single-step synthesis. The aerogels’ structures are fully characterized using a wide array of spectroscopic and microscopic methods, and heat-treated in order to make them electronically conductive. After heat treatment at 600 °C, the aerogels maintained their macrostructure and became active ORR catalysts in alkaline environment, showing high mass activity and ultra-high site density.     

Facile Synthesis of Manganese‐Oxide‐Containing Mesoporous Nitrogen‐Doped Carbon for Efficient Oxygen Reduction

Developing low‐cost non‐precious metal catalysts for high‐performance oxygen reduction reaction (ORR) is highly desirable. Here a facile, in situ template synthesis of a MnO‐containing mesoporous nitrogen‐doped carbon (m‐N‐C) nanocomposite and its high electrocatalytic activity for a four‐electron ORR in alkaline solution are reported. The synthesis of the MnO‐m‐N‐C nanocomposite involves one‐pot hydrothermal synthesis of Mn₃O₄@polyaniline core/shell nanoparticles from a mixture containing aniline, Mn(NO₃)₂, and KMnO₄, followed by heat treatment to produce N‐doped ultrathin graphitic carbon coated MnO hybrids and partial acid leaching of MnO. The as‐prepared MnO‐m‐N‐C composite catalyst exhibits high electrocatalytic activity and dominant four‐electron oxygen reduction pathway in 0.1 M KOH aqueous solution due to the synergetic effect between MnO and m‐N‐C. The pristine MnO shows little electrocatalytic activity and m‐N‐C alone exhibits a dominant two‐electron process for ORR. The MnO‐m‐N‐C composite catalyst also exhibits superior stability and methanol tolerance to a commercial Pt/C catalyst, making the composite a promising cathode catalyst for alkaline methanol fuel cell applications. The synergetic effect between MnO and N‐doped carbon described provides a new route to design advanced catalysts for energy conversion.     

Recent Progress in MOF‐Derived,Heteroatom‐Doped Porous Carbons as Highly Efficient Electrocatalysts for Oxygen Reduction Reaction in Fuel Cells

Currently, developing nonprecious‐metal catalysts to replace Pt‐based electrocatalysts in fuel cells has become a hot topic because the oxygen reduction reaction (ORR) in fuel cells often requires platinum, a precious metal, as a catalyst, which is one of the major hurdles for commercialization of the fuel cells. Recently, the newly emerging metal‐organic frameworks (MOFs) have been widely used as self‐sacrificed precursors/templates to fabricate heteroatom‐doped porous carbons. Here, the recent progress of MOF‐derived, heteroatom‐doped porous carbon catalysts for ORR in fuel cells is systematically reviewed, and the synthesis strategies for using different MOF precursors to prepare heteroatom‐doped porous carbon catalysts, including the direct carbonization of MOFs, MOF and heteroatom source mixture carbonization, and MOF‐based composite carbonization are summarized. The emphasis is placed on the precursor design of MOF‐derived metal‐free catalysts and transition‐metal‐doped carbon catalysts because the MOF precursors often determine the microstructures of the derived porous carbon catalysts. The discussion provides a useful strategy for in situ synthesis of heteroatom‐doped carbon ORR electrocatalysts by rationally designing MOF precursors. Due to the versatility of MOF structures, MOF‐derived porous carbons not only provide chances to develop highly efficient ORR electrocatalysts, but also broaden the family of nanoporous carbons for applications in supercapacitors and batteries.     

Sole Chemical Confinement of Polysulfides on Nonporous Nitrogen/Oxygen Dual‐Doped Carbon at the Kilogram Scale for Lithium–Sulfur Batteries

The exploration of inexpensive, facile, and large‐scale methods to prepare carbon scaffolds for high sulfur loadings is crucial for the advancement of Li–S batteries (LSBs). Herein, the authors report a new nitrogen and oxygen in situ dual‐doped nonporous carbonaceous material (NONPCM) that is composed of a myriad of graphene‐analogous particles. Importantly, NONPCM could be fabricated on a kilogram scale via inexpensive and green hydrothermal‐carbonization‐combined methods. Many active sites on the NONPCM surface are accessible for the efficient surface‐chemistry confinement of guest sulfur and its discharge product; this confinement is exclusive of physical entrapment, considering the low surface area. Electrochemical examination demonstrates excellent cycle stability and rate performance of the NONPCM (K)/S composite, even with a sulfur loading of 80 or 90 wt%. Hence, the scaffolds for LSBs exhibit potential for industrialization through further optimization and expansion of the present synthesis.     

In Situ Confinement Pyrolysis Transformation of ZIF‐8 to Nitrogen‐Enriched Meso‐Microporous Carbon Frameworks for Oxygen Reduction

Metal organic framework (MOF)‐derived nitrogen‐enriched nanocarbons have been proposed as promising metal‐free electrocatalysts for oxygen reduction reaction. However, the characteristic microporous feature of MOF‐derived carbon determined by the MOF structure significantly hinders the mass transfer and exposure of active sites, resulting in unsatisfactory electrocatalytic performance. Here an in situ confinement pyrolysis strategy that can simply but efficiently transform monodisperse ZIF‐8 polyhedrons to nitrogen‐enriched meso‐microporous carbon (NEMC) frameworks is reported. Using this strategy, 3D NEMC frameworks, 1D NEMC fibers, and 2D NEMC on graphene (NEMC/G) can be successfully obtained. As a metal‐free elctrocatalyst, optimized NEMC/G can reach a comparable electrocatalytic activity with superior stability and methanol resistance to commercial 30 wt% Pt/C catalyst in 0.1 m KOH solution. Such enhanced performance can be ascribed to the stable and highly open network consisting of NEMC and G with fully exposed active sites, thereby leading to durable catalytic activity.     

MO‐Co@N‐Doped Carbon (M = Zn or Co): Vital Roles of Inactive Zn and Highly Efficient Activity toward Oxygen Reduction/Evolution Reactions for Rechargeable Zn–Air Battery

A highly efficient bifunctional oxygen catalyst is required for practical applications of fuel cells and metal–air batteries, as oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are their core electrode reactions. Here, the MO‐Co@N‐doped carbon (NC, M = Zn or Co) is developed as a highly active ORR/OER bifunctional catalyst via pyrolysis of a bimetal metal–organic framework containing Zn and Co, i.e., precursor (CoZn). The vital roles of inactive Zn in developing highly active bifunctional oxygen catalysts are unraveled. When the precursors include Zn, the surface contents of pyridinic N for ORR and the surface contents of Co–N_x and Co³⁺/Co²⁺ ratios for OER are enhanced, while the high specific surface areas, high porosity, and high electrochemical active surface areas are also achieved. Furthermore, the synergistic effects between Zn‐based and Co‐based species can promote the well growth of multiwalled carbon nanotubes (MWCNTs) at high pyrolysis temperatures (≥700 °C), which is favorable for charge transfer. The optimized CoZn‐NC‐700 shows the highly bifunctional ORR/OER activity and the excellent durability during the ORR/OER processes, even better than 20 wt% Pt/C (for ORR) and IrO₂ (for OER). CoZn‐NC‐700 also exhibits the prominent Zn–air battery performance and even outperforms the mixture of 20 wt% Pt/C and IrO₂.     

Shape Control of Mn3O4 Nanoparticles on Nitrogen‐Doped Graphene for Enhanced Oxygen Reduction Activity

Three kinds of Mn₃O₄ nanoparticles with different shapes (spheres, cubes, and ellipsoids) are selectively grown on nitrogen‐doped graphene sheets through a two‐step liquid‐phase procedure. These non‐precious hybrid materials display an excellent ORR activity and good durability. The mesoporous microstructure, nitrogen doping, and strong bonding between metal species and doped graphene are found to facilitate the ORR catalytic process. Among these three kinds of Mn₃O₄ particles, the ellipsoidal particles on nitrogen‐doped graphene exhibit the highest ORR activity with a more positive onset‐potential of –0.13 V (close to that of Pt/C, –0.09 V) and a higher kinetic limiting current density (J_K) of 11.69 mA cm^–2 at –0.60 V. It is found that the ORR performance of hybrid materials can be correlated to the shape of Mn₃O₄ nanocrystals, and specifically to the exposed crystalline facets associated with a given shape. The shape dependence of Mn₃O₄ nanoparticles integrated with nitrogen‐doped graphene on the ORR performance, reported here for the first time, may advance the development of fuel cells and metal‐air batteries.     

Ultra‐High Surface Area Nitrogen‐Doped Carbon Aerogels Derived From a Schiff‐Base Porous Organic Polymer Aerogel for CO2 Storage and Supercapacitors

Nitrogen‐doped carbon aerogels (NCAs) have received great attention for a wide range of applications, from thermal electronics to waste water purification, heavy metal or gas adsorption, energy storage, and catalyst supports. Herein NCAs are developed via the synthesis of a Schiff‐base porous organic polymer aerogel followed by pyrolysis. By controlling the pyrolysis temperature, the polymer aerogel can be simply converted into porous NCAs with a low bulk density (5 mg cm^?3), high surface area (2356 m² g^?1), and high bulk porosity (70%). The NCAs containing 1.8–5.3 wt% N atoms exhibit remarkable CO₂ uptake capacities (6.1 mmol g^?1 at 273 K and 1 bar, 33.1 mmol g^?1 at 323 K and 30 bar) and high ideal adsorption solution theory selectivity (47.8) at ambient pressure. Supercapacitors fabricated with NCAs display high specific capacitance (300 F g^?1 at 0.5 A g^?1), fast rate (charge to 221 F g^?1 within only 17 s), and high stability (retained >98% capacity after 5000 cycles). Asymmetric supercapacitors assembled with NCAs also show high energy density and power density with maximal values of 30.5 Wh kg^?1 and 7088 W kg^?1, respectively. The outstanding CO₂ uptake and energy storage abilities are attributed to the ultra‐high surface area, N‐doping, conductivity, and rigidity of NCA frameworks.     

Sulfur‐Enriched Conjugated Polymer Nanosheet Derived Sulfur and Nitrogen co‐Doped Porous Carbon Nanosheets as Electrocatalysts for Oxygen Reduction Reaction and Zinc–Air Battery

Among the rising 2D soft materials, conjugated polymer nanosheets are one of the most promising and new classes of polymeric materials, which are rarely developed because of the challenge in controlling the dimensionality and lack of synthetic strategies. In this study, one kind of sulfur‐enriched conjugated polymer nanosheet (2DP‐S) with a high aspect ratio of up to ≈400 is successfully synthesized. On the basis of structural characterization, as‐prepared 2DP‐S possesses the chemical identity of cruciform‐fused polymeric backbone consisting of quinoidal polythiophene and poly(p‐phenylenevinylene) along horizontal and vertical directions, respectively, by sharing two alternating single–double carbon–carbon bonds in each repeat unit. The unique structural conformation of 2DP‐S renders carrier mobilities of up to 0.1 ± 0.05 cm² V^?1 s^?1, a figure inferred from Terahertz time domain spectroscopy. Moreover, upon thermal treatment, 2DP‐S is readily converted into N/S dual‐doped porous carbon nanosheets (2DPCs) under ammonia atmosphere, whose N/S ratio can be rationally controlled by adjusting the activation time. The catalytic performance of the oxygen reduction reaction of as‐prepared 2DPCs is well tunable by the rationally controlled N/S contents. These results offer a new pathway for exploring heteroatom‐doped porous carbons applicable for energy conversion and storage.     

Ag Anchored Atomically Around Nanopores of Porous Co(OH)2 for Efficient Bifunctional Oxygen Catalysis

Various clean energy storage and conversion systems highly depend on rational design of efficient electrocatalysts for oxygen reactions. Increasing both gas molecular diffusion and intrinsic activity is critical to boosting its efficiency for bifunctional oxygen electrocatalysis. However, controllable synthesis of catalysts that combines gas molecular diffusion and intrinsic activity remains a fundamental challenge. Herein, a two-step synthetic strategy is adopted to fabricate a composite oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) bifunctional catalyst (P-Ag-Co(OH)₂), of which, atomic Ag is anchored in reactive oxygen atoms around nanopores of Co(OH)₂ nanosheets. Abundant nanopores provide enough gas molecular diffusion channels, and the special Ag-O-Co-OH catalytic groups around nanopores display high intrinsic catalytic activity, which jointly result in an excellent ORR/OER performance. In alkaline electrolyte, P-Ag-Co(OH)₂ displays a high half-wave potential (0.902 V versus RHE) for ORR, and a low overpotential (235 mV at 10 mA cm⁻²) for OER, which is superior to non-noble catalysts in previous studies and Pt/C (Ir/C) catalyst. At the same time, the single-cell zinc-air battery is prepared with an extremely high discharge peak power density of 435 mW cm⁻² and excellent discharge–charge cycle stability.     

Defect‐Rich Nitrogen Doped Co3O4/C Porous Nanocubes Enable High‐Efficiency Bifunctional Oxygen Electrocatalysis

Heteroatom doping plays a significant role in optimizing the catalytic performance of electrocatalysts. However, research on heteroatom doped electrocatalysts with abundant defects and well‐defined morphology remain a great challenge. Herein, a class of defect‐engineered nitrogen‐doped Co₃O₄ nanoparticles/nitrogen‐doped carbon framework (N‐Co₃O₄@NC) strongly coupled porous nanocubes, made using a zeolitic imidazolate framework‐67 via a controllable N‐doping strategy, is demonstrated for achieving remarkable oxygen evolution reaction (OER) catalysis. X‐ray photoelectron spectroscopy, X‐ray absorption fine structure, and electron spin resonance results clearly reveal the formation of a considerable amount of nitrogen dopants and oxygen vacancies in N‐Co₃O₄@NC. The defect engineering of N‐Co₃O₄@NC makes it exhibit an overpotential of only 266 mV to reach 10 mA cm^?2, a low Tafel slope of 54.9 mV dec^?1 and superior catalytic stability for OER, which is comparable to that of commercial RuO₂. Density functional theory calculations indicate N‐doping could promote catalytic activity via improving electronic conductivity, accelerating reaction kinetics, and optimizing the adsorption energy for intermediates of OER. Interestingly, N‐Co₃O₄@NC also shows a superior oxygen reduction reaction activity, making it a bifunctional electrocatalyst for zinc–air batteries. The zinc–air battery with the N‐Co₃O₄@NC cathode demonstrates superior efficiency and durability, showing the feasibility of N‐Co₃O₄/NC in electrochemical energy devices.     

Bifunctional Covalent Organic Framework-Derived Electrocatalysts with Modulated p-Band Centers for Rechargeable Zn–Air Batteries

Fine control over the physicochemical structures of carbon electrocatalysts is important for improving the sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in rechargeable Zn–air batteries. Covalent organic frameworks (COFs) are considered good candidate carbon materials because their structures can be precisely controlled. However, it remains a challenge to impart bifunctional electrocatalytic activities for both the ORR and OER to COFs. Herein, a pyridine-linked triazine covalent organic framework (PTCOF) with well-defined active sites and pores is readily prepared under mild conditions, and its electronic structure is modulated by incorporating Co nanoparticles (CoNP-PTCOF) to induce bifunctional electrocatalytic activities for the ORR and OER. The CoNP-PTCOF exhibits lower overpotentials for both ORR and OER with outstanding stability. Computational simulations find that the p-band center of CoNP-PTCOF down-shifted by charge transfer, compared to pristine PTCOF, facilitate the adsorption and desorption of oxygen intermediates on the pyridinic carbon active sites during the reactions. The Zn–air battery assembled with bifunctional CoNP-PTCOF exhibits a small voltage gap of 0.83 V and superior durability for 720 cycles as compared with a battery containing commercial Pt/C and RuO₂. This strategy for modulating COF electrocatalytic activities can be extended for designing diverse carbon electrocatalysts.     

Hollow Loofah‐Like N,O‐Co‐Doped Carbon Tube for Electrocatalysis of Oxygen Reduction

Designing a highly active doped‐carbon‐based oxygen reduction reaction (ORR) electrocatalyst with optimal stability is a must if large‐scale implementations of fuel cells are to be realized. Developing controllable doping strategies is essential for achieving highly active catalysts. Herein, a facile doping strategy is developed by designing a precursor material with unique core–shell nanostructure, whereby the Materials Institute Lavoisier (MIL) metal–organic framework (MOF) and polyaniline are core and shell components, and serving as oxygen and nitrogen precursors, respectively. A novel hollow loofah‐like carbon tube (HLCT) catalyst is derived from precursor material with controllable heteroatom‐doping concentrations through modulating the mass ratio of MOF/aniline. The optimal HLCT‐1/2 catalyst, with a MOF/aniline mass ratio of 1/2, exhibits excellent ORR activity and stability in an alkaline medium. Remarkably, the half‐wave potential (0.88 V) and the current density (4.35 mA cm^?2) at 0.85 V of HLCT‐1/2 catalyst surpass that of commercial Pt/C. Such superior catalytic properties can be attributed to the high specific surface area and abundant active sites of loofah‐shape carbon tubes. Moreover, the O dopant modulates the content and distribution of N species, leading to the enhanced adsorption strength of oxygen molecules on catalyst surface, promoting the activation of oxygen, and thus achieving higher electrocatalytic activity.     

Controlled Fabrication of Hierarchically Structured Nitrogen‐Doped Carbon Nanotubes as a Highly Active Bifunctional Oxygen Electrocatalyst

Hierarchically structured nitrogen‐doped carbon nanotube (NCNT) composites, with copper (Cu) nanoparticles embedded uniformly within the nanotube walls and cobalt oxide (Co_xO_y) nanoparticles decorated on the nanotube surfaces, are fabricated via a combinational process. This process involves the growth of Cu embedded CNTs by low‐ and high‐temperature chemical vapor deposition, post‐treatment with ammonia for nitrogen doping of these CNTs, precipitation‐assisted separation of NCNTs from cobalt nitrate aqueous solution, and finally thermal annealing for Co_xO_y decoration. Theoretical calculations show that interaction of Cu nanoparticles with CNT walls can effectively decrease the work function of CNT surfaces and improve adsorption of hydroxyl ions onto the CNT surfaces. Thus, the activities of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are significantly enhanced. Because of this benefit, further nitrogen doping, and synergistic coupling between Co_xO_y and NCNTs, Cu@NCNT/Co_xO_y composites exhibit ORR activity comparable to that of commercial Pt/C catalysts and high OER activity (outperforming that of IrO₂ catalysts). More importantly, the composites display superior long‐term stability for both ORR and OER. This simple but general synthesis protocol can be extended to design and synthesis of other metal/metal oxide systems for fabrication of high‐performance carbon‐based electrocatalysts with multifunctional catalytic activities.     

An Advanced Nitrogen‐Doped Graphene/Cobalt‐Embedded Porous Carbon Polyhedron Hybrid for Efficient Catalysis of Oxygen Reduction and Water Splitting

A novel hybrid electrocatalyst consisting of nitrogen‐doped graphene/cobalt‐embedded porous carbon polyhedron (N/Co‐doped PCP//NRGO) is prepared through simple pyrolysis of graphene oxide‐supported cobalt‐based zeolitic imidazolate‐frameworks. Remarkable features of the porous carbon structure, N/Co‐doping effect, introduction of NRGO, and good contact between N/Co‐doped PCP and NRGO result in a high catalytic efficiency. The hybrid shows excellent electrocatalytic activities and kinetics for oxygen reduction reaction in basic media, which compares favorably with those of the Pt/C catalyst, together with superior durability, a four‐electron pathway, and excellent methanol tolerance. The hybrid also exhibits superior performance for hydrogen evolution reaction, offering a low onset overpotential of 58 mV and a stable current density of 10 mA cm^?2 at 229 mV in acid media, as well as good catalytic performance for oxygen evolution reaction (a small overpotential of 1.66 V for 10 mA cm^?2 current density). The dual‐active‐site mechanism originating from synergic effects between N/Co‐doped PCP and NRGO is responsible for the excellent performance of the hybrid. This development offers an attractive catalyst material for large‐scale fuel cells and water splitting technologies.     

Nitrogen‐Doped Mesoporous Carbon Promoted Chemical Adsorption of Sulfur and Fabrication of High‐Areal‐Capacity Sulfur Cathode with Exceptional Cycling Stability for Lithium‐Sulfur Batteries

As one important component of sulfur cathodes, the carbon host plays a key role in the electrochemical performance of lithium‐sulfur (Li‐S) batteries. In this paper, a mesoporous nitrogen‐doped carbon (MPNC)‐sulfur nanocomposite is reported as a novel cathode for advanced Li‐S batteries. The nitrogen doping in the MPNC material can effectively promote chemical adsorption between sulfur atoms and oxygen functional groups on the carbon, as verified by X‐ray absorption near edge structure spectroscopy, and the mechanism by which nitrogen enables the behavior is further revealed by density functional theory calculations. Based on the advantages of the porous structure and nitrogen doping, the MPNC‐sulfur cathodes show excellent cycling stability (95% retention within 100 cycles) at a high current density of 0.7 mAh cm^‐2 with a high sulfur loading (4.2 mg S cm^‐2) and a sulfur content (70 wt%). A high areal capacity (≈3.3 mAh cm^‐2) is demonstrated by using the novel cathode, which is crucial for the practical application of Li‐S batteries. It is believed that the important role of nitrogen doping promoted chemical adsorption can be extended for development of other high performance carbon‐sulfur composite cathodes for Li‐S batteries.     

Rapid Inversion of Surface Charges in Heteroatom‐Doped Porous Carbon: A Route to Robust Electrochemical Desalination

Given that a considerably large population suffers from shortage of water, there are numerous on‐going efforts to turn seawater into freshwater, and electrochemical desalination processes—particularly capacitive deionization (CDI)—have gained significant attention due to their high energy efficiency and reliable performance. Meanwhile, carbonaceous electrode materials, which are most commonly used in CDI systems, have poor long‐term stability due to unfavorable interactions with oxygen in saline water. Herein, rapid and vigorous inversion of surface charges in heteroatom‐doped carbon electrodes, which leads to a robust operation of CDI with high desalination capacity, is reported for the first time. By carbonization of coffee wastes, nitrogen‐ and sulfur‐codoped activated carbon with hierarchical micro/mesopores are prepared in an environmentally‐friendly manner, and this carbon results in a significantly higher inverted capacity than that of various activated carbon counterparts in long‐term CDI operations, without any sign of drop in performance. Investigations on the changes in physicochemical properties of the electrodes during the inversion disclose the favorable roles of nitrogen and sulfur dopants, which can be summarized as enlarging the difference between the surface charges of the two electrodes by chemical interactions with oxygen in the anode and carbon in the cathode.     

Nitrogen‐Doped Nanoporous Carbon/Graphene Nano‐Sandwiches: Synthesis and Application for Efficient Oxygen Reduction

A zeolitic‐imidazolate‐framework (ZIF) nanocrystal layer‐protected carbonization route is developed to prepare N‐doped nanoporous carbon/graphene nano‐sandwiches. The ZIF/graphene oxide/ZIF sandwich‐like structure with ultrasmall ZIF nanocrystals (i.e., ≈20 nm) fully covering the graphene oxide (GO) is prepared via a homogenous nucleation followed by a uniform deposition and confined growth process. The uniform coating of ZIF nanocrystals on the GO layer can effectively inhibit the agglomeration of GO during high‐temperature treatment (800 °C). After carbonization and acid etching, N‐doped nanoporous carbon/graphene nanosheets are formed, with a high specific surface area (1170 m² g^?1). These N‐doped nanoporous carbon/graphene nanosheets are used as the nonprecious metal electrocatalysts for oxygen reduction and exhibit a high onset potential (0.92 V vs reversible hydrogen electrode; RHE) and a large limiting current density (5.2 mA cm^?2 at 0.60 V). To further increase the oxygen reduction performance, nanoporous Co‐N_x/carbon nanosheets are also prepared by using cobalt nitrate and zinc nitrate as cometal sources, which reveal higher onset potential (0.96 V) than both commercial Pt/C (0.94 V) and N‐doped nanoporous carbon/graphene nanosheets. Such nanoporous Co‐N_x/carbon nanosheets also exhibit good performance such as high activity, stability, and methanol tolerance in acidic media.     

Oxygen/Fluorine Dual‐Doped Porous Carbon Nanopolyhedra Enabled Ultrafast and Highly Stable Potassium Storage

Carbon‐based materials are promising anodes for potassium‐ion batteries (PIBs). However, due to the significant volume expansion and structural instability, it is still a challenge to achieve a high capacity, high rate and long cycle life for carbonaceous anodes. Herein, oxygen/fluorine dual‐doped porous carbon nanopolyhedra (OFPCN) is reported for the first time as a novel anode for PIBs, which exhibits a high reversible capacity of 481 mA h g^?1 at 0.05 A g^?1 and excellent performance of 218 mA h g^?1 after 2000 cycles at 1 A g^?1 with 92% capacity retention. Even after 5000 robust cycles at 10 A g^?1 with charging/discharging time of around 40 s, an unprecedented capacity of 111 mA h g^?1 is still maintained. Such ultrafast potassium storage and unprecedented cycling stability have been seldom reported in PIBs. Quantitative kinetics analysis reveals that both diffusion and capacitance processes are involved in the potassium storage mechanism. Density functional theory calculations demonstrate that the O/F dual‐doped porous carbon promotes the K‐adsorption ability and can absorb multiple K atoms with slight structural distortion, which accounts for the high specific capacity, outstanding rate capability, and excellent cycling stability of the OFPCN anode.