A General Self-Sacrifice Template Strategy to 3D Heteroatom-Doped Macroporous Carbon for High-Performance Potassium-Ion Hybrid Capacitors

Novel Bilayer-Shelled N, O-Doped Hollow Porous Carbon Microspheres as High Performance Anode for Potassium-Ion Hybrid Capacitors

With the advantages of high energy/power density, long cycling life and low cost, dual-carbon potassium ion hybrid capacitors (PIHCs) have great potential in the field of energy storage. Here, a novel bilayer-shelled N, O-doped hollow porous carbon microspheres (NOHPC) anode has been prepared by a self-template method, which is consisted of a dense thin shell and a hollow porous spherical core. Excitingly, the NOHPC anode possesses a high K-storage capacity of 325.9 mA h g-1 at 0.1 A g-1 and a capacity of 201.1 mAh g-1 at 5 A g-1 after 6000 cycles. In combination with ex situ characterizations and density functional theory calculations, the high reversible capacity has been demonstrated to be attributed to the co-doping of N/O heteroatoms and porous structure improved K+ adsorption and intercalation capabilities, and the stable long-cycling performance originating from the bilayer-shelled hollow porous carbon sphere structure. Meanwhile, the hollow porous activated carbon microspheres (HPAC) cathode with a high specific surface area (1472.65 m2 g-1) deriving from etching NOHPC with KOH, contributing to a high electrochemical adsorption capacity of 71.2 mAh g-1 at 1 A g-1. Notably, the NOHPC//HPAC PIHC delivers a high energy density of 90.1 Wh kg-1 at a power density of 939.6 W kg-1 after 6000 consecutive charge-discharge cycles.

Engineering the First Coordination Shell of Single Zn Atoms via Molecular Design Strategy toward High-Performance Sodium-Ion Hybrid Capacitors

Atomically dispersed Zn moieties are efficient active sites for accelerating the electrode kinetics of carbons for sodium-ion hybrid capacitors (SIHCs), but the low utilization and symmetric configuration of Zn single-atom greatly hamper the Na ion storage capability. Herein, a molecular design strategy is employed to synthesize high-density Zn single atoms with asymmetric Zn-N₃ S coordination embedded in nitrogen/sulfur codoped carbon (Zn-N₃ S-NSC). The key to this strategy lies in the Zn power-catalyzed condensation of trithiocyanuric acid molecules to generate S-doped g-C₃ N₄ , which can in situ coordinate with Zn sources to form Zn-N₃ S moieties during pyrolysis. By virtue of the highly exposed Zn-N₃ S moieties, Zn-N₃ S-NSC presents ultrahigh reactivity, efficient electron transfer, and decreased ion diffusion barriers for SIHCs, rendering an impressive energy density of 215 Wh kg^-1 and a maximum power density of 15625 W kg^-1 . Moreover, the pouch cell displays a high capacity of 279 mAh g^-1 after 4000 cycles. This work provides a new avenue for the regulation of the coordination configuration of single metal atoms in carbons toward high-performance electrochemical energy technologies at the molecular level.

Russian-Doll-Like Porous Carbon as Anode Materials for High-Performance Potassium-Ion Hybrid Capacitors

Pore-structure design with the sophisticated and pragmatic nanostructures still remains a great challenge. In this work, porous carbon with Russian-doll-like pores rather than traditional single modal is fabricated via a boiling carbonization approach, accompanied by K⁺ -pre-intercalation. The most important internal factor is that alkali can penetrate into the stereoscopic space of layered Malonic acid dihydrazide and the confinement effect leads to the in-depth development of different dimensional pore structures. The oxygenated and nitrogenated surface guarantees the K⁺ intercalation behavior. Benefiting from their open framework and enlarged interlayer spacing, K⁺ -pre-intercalated porous carbon with Russian-doll-like pores (denoted as KPCRPs) as anode material exhibits promising potassium storage performance. The assembled KPCRP//activated carbon potassium-ion hybrid supercapacitor in 30 m CH₃ COOK displays a high energy density of 157.29 Wh kg^-1 , an ultrahigh power output of 14 kW kg^-1 , and a long cycling life (99.58% capacity retention after 10000 cycles), highlighting the superiority of Russian-doll-like pore structure. This work sheds light on the designing of 3D pores structure, especially for multimodal pore architectures.

In Situ Generation of Vertically Crossed P-Cu3Se2 Ultrathin Nanosheets Derived from Cu2S Nanorod Arrays for High-Performance Supercapacitors

Transition-metal selenides (TMSs) have great potential in the synthesis of supercapacitor electrode materials due to their rich content and high specific capacity. However, the aggregation phenomenon of TMS materials in the process of charging and discharging will cause capacity attenuation, which seriously affects the service life and practical applications. Therefore, it is of great practical significance to design simple and efficient synthesis strategies to overcome these shortcomings. Hence, P-doped Cu₃Se₂ nanosheets are loaded on vertically aligned Cu₂S nanorod arrays to synthesize CF/Cu₂S@Cu₃Se₂/P nanocomposites with a unique core-shell heterostructure. Notably, the Cu₂S precursors can be rapidly converted into Cu₃Se₂ nanorod arrays in situ in just 30 min at room temperature. The unique core-shell heterostructure effectively avoids the aggregation phenomenon, and the doped P elements further enhance the electrochemical properties of the electrode materials. Therefore, the as-prepared CF/Cu₂S@Cu₃Se₂/P electrode exhibits a high areal capacitance of 5054 mF cm^-2 (1099 C g^-1) at 3 mA cm^-2 and still retains 90.2% capacitance after 10 000 galvanostatic charge-discharge (GCD) cycles. The asymmetric supercapacitor (ASC) device assembled from synthetic CF/Cu₂S@Cu₃Se₂/P and activated carbon (AC) possesses an energy density of 41.1 Wh kg^-1 at a power density of 480.4 W kg^-1. This work shows that the designed CF/Cu₂S@Cu₃Se₂/P electrode has broad application prospects in the field of electrochemical energy storage.

Electrostatic Interaction in Amino Protonated Chitosan-Metal Complex Anion Hydrogels: A Simple Approach to Porous Metal Carbides/N-Doped Carbon Aerogels for Energy Conversion

In the face of the increasingly serious rapid depletion of fossil fuels, exploring alternative energy conversion technologies may be a promising choice to alleviate this crisis. Transition metal carbides (TMCs)/carbon composites are considered as prospective electrocatalysts due to their high catalytic activities and structural stability. In this work, we report the simple synthesis of TMCs/N-doping carbon aerogels (TMCs/NCAs, including Fe₃C/NCA, Mo₃C₂/NCA, and Fe₃C-Mo₂C/NCA) for the oxygen reduction reaction (ORR) using protonated chitosan/metal complex anion-chelated aerogels. Among them, the Fe₃C/NCA composite possesses efficient ORR activity (similar to Pt/C), and the Fe₃C/NCA-assembled Zn-air battery exhibits high power densities of about 250 mW cm^-2. The density functional theory calculation reveals that the presence of graphite-N, pyridine-N, and carbon defects in the carbon framework effectively reduces the free energy of ORR occurring in Fe₃C. This work provides a simple and extensible strategy for the preparation of TMCs from chitosan, which is expected to be extended to other metal carbides.

Homologous Nitrogen-Doped Hierarchical Carbon Architectures Enabling Compatible Anode and Cathode for Potassium-Ion Hybrid Capacitors

Potassium-ion hybrid capacitors (PIHCs) have been considered as an emerging device to render grid-scale energy storage. Nevertheless, the sluggish kinetics at the anode side and limited capacity output at the cathode side remain daunting challenges for the overall performances of PIHCs. Herein, an exquisite "homologous strategy" to devise multi-dimensional N-doped carbon nanopolyhedron@nanosheet anode and activated N-doped hierarchical carbon cathode targeting high-performance PIHCs is reported. The anode material harnessing a dual-carbon structure and the cathode candidate affording a high specific surface area (2651 m² g^-1 ) act in concert with a concentrated ether-based electrolyte, resulting in an excellent half cell performance. The related storage mechanism is systematically revealed by in situ electrokinetic characterizations. More encouragingly, the thus-derived PIHC full cell demonstrates a favorable energy output (157 Wh kg^-1 ), showing distinct advantages over the state-of-the-art PIHC counterparts.

Recent Progress on Asymmetric Carbon- and Silica-Based Nanomaterials: From Synthetic Strategies to Their Applications

HIGHLIGHTS

The synthetic strategies and fundamental mechanisms of various asymmetric carbon- and silica-based nanomaterials were systematically summarized. The advantages of asymmetric structure on their related applications were clarified by some representative applications of asymmetric carbon- and silica-based nanomaterials. The future development prospects and challenges of asymmetric carbon- and silica-based nanomaterials were proposed.

ABSTRACT

Carbon- and silica-based nanomaterials possess a set of merits including large surface area, good structural stability, diversified morphology, adjustable structure, and biocompatibility. These outstanding features make them widely applied in different fields. However, limited by the surface free energy effect, the current studies mainly focus on the symmetric structures, such as nanospheres, nanoflowers, nanowires, nanosheets, and core–shell structured composites. By comparison, the asymmetric structure with ingenious adjustability not only exhibits a larger effective surface area accompanied with more active sites, but also enables each component to work independently or corporately to harness their own merits, thus showing the unusual performances in some specific applications. The current review mainly focuses on the recent progress of design principles and synthesis methods of asymmetric carbon- and silica-based nanomaterials, and their applications in energy storage, catalysis, and biomedicine. Particularly, we provide some deep insights into their unique advantages in related fields from the perspective of materials’ structure–performance relationship. Furthermore, the challenges and development prospects on the synthesis and applications of asymmetric carbon- and silica-based nanomaterials are also presented and highlighted. [Image: see text]