Lignin is the second most abundant and the only nature polymer rich in aromatic units. Although aromatic-unit-rich precursors often yield soft carbon after carbonization, the side chains in lignin ...crosslink with the aromatic units and form a rigid three-dimensional (3D) structure which eventually leads to hard carbons. Through a graphene oxide-catalyzed decomposition and repolymerization process, we successfully reconstructed lignin by partially tailoring the side chains. Compared to directly carbonized lignin, the carbonized reconstructed lignin possesses significantly fewer defects, 86% fewer oxygen-functionalities, 82% fewer micropores, and narrower interlayer space. These parameters can be tuned by the amount of catalysts (graphene oxide). When tested as anode for K-ion and Na-ion batteries, the carbonized reconstructed lignin delivers notably higher capacity at low-potential range (especially for Na-storage), shows much-improved performance at high current density, and most importantly, reduces voltage hysteresis between discharge and charge process by more than 50%, which is critical to the energy efficiency of the energy storage system. Our study reveals that the voltage hysteresis in K-storage is much severer than that in Na-storage for all samples. For practical K-ion battery applications, the voltage hysteresis deserves more attention in future electrode materials design and the reconstruct ion strategy introduced in this work provides potential low-cost solution.
Metal oxides of earth‐abundant elements are promising electrocatalysts to overcome the sluggish oxygen evolution and oxygen reduction reaction (OER/ORR) in many electrochemical energy‐conversion ...devices. However, it is difficult to control their catalytic activity precisely. Here, a general three‐stage synthesis strategy is described to produce a family of hybrid materials comprising amorphous bimetallic oxide nanoparticles anchored on N‐doped reduced graphene oxide with simultaneous control of nanoparticle elemental composition, size, and crystallinity. Amorphous Fe0.5Co0.5Ox is obtained from Prussian blue analog nanocrystals, showing excellent OER activity with a Tafel slope of 30.1 mV dec−1 and an overpotential of 257 mV for 10 mA cm−2 and superior ORR activity with a large limiting current density of −5.25 mA cm−2 at 0.6 V. A fabricated Zn–air battery delivers a specific capacity of 756 mA h gZn−1 (corresponding to an energy density of 904 W h kgZn−1), a peak power density of 86 mW cm−2 and can be cycled over 120 h at 10 mA cm−2. Other two amorphous bimetallic, Ni0.4Fe0.6Ox and Ni0.33Co0.67Ox, are also produced to demonstrate the general applicability of this method for synthesizing binary metal oxides with controllable structures as electrocatalysts for energy conversion.
Simultaneous control of bimetallic oxide nanoparticle elemental composition, size, and crystallinity yields a high‐performance bifunctional oxygen evolution and reduction electrocatalyst for rechargeable Zn–air batteries. This method has general applicability toward various binary, tertiary, or even quadruple metal systems.
Abstract
Aqueous zinc (Zn) chemistry features intrinsic safety, but suffers from severe irreversibility, as exemplified by low Coulombic efficiency, sustained water consumption and dendrite growth, ...which hampers practical applications of rechargeable Zn batteries. Herein, we report a highly reversible aqueous Zn battery in which the graphitic carbon nitride quantum dots additive serves as fast colloid ion carriers and assists the construction of a dynamic & self-repairing protective interphase. This real-time assembled interphase enables an ion-sieving effect and is found actively regenerate in each battery cycle, in effect endowing the system with single Zn
2+
conduction and constant conformal integrality, executing timely adaption of Zn deposition, thus retaining sustainable long-term protective effect. In consequence, dendrite-free Zn plating/stripping at ~99.6% Coulombic efficiency for 200 cycles, steady charge-discharge for 1200 h, and impressive cyclability (61.2% retention for 500 cycles in a Zn | |MnO
2
full battery, 73.2% retention for 500 cycles in a Zn | |V
2
O
5
full battery and 93.5% retention for 3000 cycles in a Zn | |VOPO
4
full battery) are achieved, which defines a general pathway to challenge Lithium in all low-cost, large-scale applications.
Biodegradable food packaging promises a more sustainable future. Among the many different biopolymers used, poly(lactic acid) (PLA) possesses the good mechanical property and cost-effectiveness ...necessary of a biodegradable food packaging. However, PLA food packaging suffers from poor water vapor and oxygen barrier properties compared to many petroleum-derived ones. A key challenge is, therefore, to simultaneously enhance both the water vapor and oxygen barrier properties of the PLA food packaging. To address this issue, we design a sandwich-architectured PLA–graphene composite film, which utilizes an impermeable reduced graphene oxide (rGO) as the core barrier and commercial PLA films as the outer protective encapsulation. The synergy between the barrier and the protective encapsulation results in a significant 87.6% reduction in the water vapor permeability. At the same time, the oxygen permeability is reduced by two orders of magnitude when evaluated under both dry and humid conditions. The excellent barrier properties can be attributed to the compact lamellar microstructure and the hydrophobicity of the rGO core barrier. Mechanistic analysis shows that the large rGO lateral dimension and the small interlayer spacing between the rGO sheets have created an extensive and tortuous diffusion pathway, which is up to 1450-times the thickness of the rGO barrier. In addition, the sandwiched architecture has imbued the PLA–rGO composite film with good processability, which increases the manageability of the film and its competency to be tailored. Simulations using the PLA–rGO composite food packaging film for edible oil and potato chips also exhibit at least eight-fold extension in the shelf life of these oxygen and moisture sensitive food products. Overall, these qualities have demonstrated the high potential of a sandwich-architectured PLA–graphene composite film for food packaging applications.
Translating the advantages of carbon nanomaterials into macroscopic energy storage devices is challenging because the desirable nanoscale properties often disappear during assembly processes. Here we ...describe a new nonequilibrium subcritical hydrothermal method capable of independently manipulating the temperature and pressure to create unique assembly conditions crossing the commonly used liquid-vapor boundary. Highly conductive and dense-packed yet ion-accessible nanocarbon microfibers can be obtained from graphene oxide sheets, single-walled carbon nanotubes, and a nitrogen-doping crosslinker under 20 min of hydrothermal assembly, 80% energy saving compared to standard hydrothermal methods, and one of the shortest time in the field of hydrothermal processing of carbon nanomaterials. Using those microfibers, we built microsupercapacitors that reach a high volumetric capacitance of 52 F cm−3, energy density of 7.1 mWh cm−3, and power density of 1645.7 mW cm−3, respectively. We further demonstrate the 3D integration of multiple fiber microsupercapacitors that reduces the device footprint by 75% while expanding the operational voltage and current window. This strategy is a promising tool for harmoniously assembling carbon nanostructures as energy storage components for various energy applications.
A new hydrothermal system is capable of controlling the temperature and pressure of water independently to create unique hydrothermal assembly conditions for achieving ultrafast assembly of carbon nanomaterials into carbon architectures. Display omitted
1D supercapacitors (SCs) have emerged as promising candidates to power emerging electronics in recent years because of their unique advantages in energy storage and mechanical flexibility. There are ...four main research fronts in the development of 1D SCs: 1) enhancing mechanical characteristics, 2) achieving superior electrochemical performance, 3) enabling multiple device integration, and 4) demonstrating multifunctionality. Here, a brief history of 1D SCs is presented and significant research achievements regarding the four fronts identified as the main pillars of the development of 1D SCs are highlighted. The current challenges of the fabrication and utilization of 1D SCs are critically examined and potential solutions are analyzed. Plus, the performance inconsistencies arising from the improper use and extreme diversity of performance evaluation and reporting methods are highlighted. Beyond, perspectives on future efforts are provided and goals regarding the four research fronts are set, to further push 1D SCs toward practical applications. The development of 1D SCs is summarized here, with existing obstacles diagnosed, corresponding solutions proposed, and future directions indicated accordingly.
1D supercapacitors have emerged as promising candidates to power emerging electronics. There are four research fronts, including: 1) enhancing mechanical characteristics, 2) achieving superior electrochemical performance, 3) enabling multiple device integration, and 4) demonstrating multifunctionality. Recent research achievements are summarized, existing obstacles are diagnosed, corresponding solutions are proposed, and future directions are indicated.
A facile activation strategy can transform pristine carbon fiber tows into high‐performance fiber electrodes with a specific capacitance of 14.2 F cm−3. The knottable fiber supercapacitor shows an ...energy density of 0.35 mW h cm−3, an ultrahigh power density of 3000 mW cm−3, and a remarkable capacitance retention of 68%, when the scan rate increases from 10 to 1000 mV s−1.
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•The functions of reactive sites in electrocatalytic NRR and the electrocatalytic NRR mechanism are introduced.•The typical strategies to construct and characterize atomic-level ...reactive sites are summarized.•The recent theoretical and experimental advances of single-atoms, dual-atoms, metal clusters, vacancies, and dopants in electrocatalytic NRR are discussed.•The rigorous protocols for electrocatalytic NRR are listed.•The challenges and perspectives of atomic-level reactive sites in electrocatalytic NRR are proposed.
Ammonia (NH3) is an integral part to modern agriculture and industry. As an economical and sustainable process to convert nitrogen to NH3 under ambient conditions, the electrocatalytic nitrogen reduction reaction (NRR) strategy has attracted considerable attention in recent years. The fabrication of atomic-level reactive sites provides an opportunity to develop novel atomic-scale catalysts with excellent electrocatalytic NRR performance. In particular, the design of atomic-level reactive sites can not only improve the activity, selectivity, and durability for electrocatalytic NRR, but also deepen the understanding of the reaction mechanism. In this review, the roles of reactive sites in electrocatalytic NRR and the electrocatalytic NRR mechanism are introduced first. Then the typical strategies to construct and characterize atomic-level reactive sites are summarized. Next, the recent progress in rational design and development of atomic-level reactive sites for electrocatalytic NRR is summarized and discussed, with a focus on single-atoms, dual-atoms, metal clusters, vacancies, and dopants. Additionally, the rigorous protocols for electrocatalytic NRR are listed. Finally, the challenges and perspectives of atomic-level reactive sites in electrocatalytic NRR are proposed to develop more credible high-efficiency NRR electrocatalysts.
Despite the advantages of the fiber‐shaped Zn‐ion microbattery (FZMB) in powering wearable electronics, several fundamental challenges hinder its practical application, mainly including dendrite ...growth on Zn anodes (leading to short cycle life) and low electrical conductivity of cathode (resulting in poor rate performance). Herein, a facile approach of sputtering a nano‐thin conductive carbon layer on Zn anode to effectively suppress dendrite growth and a dual‐conductive polymer strategy to fabricate ultraconductive core‐sheath fiber cathode (poly(3,4‐ethylenedioxythiophene)‐poly(styrene sulfonate) (PEDOT:PSS) fiber@polyaniline nanobulges) are demonstrated. The carbon layer suppresses Zn dendrites by uniformizing surface electric field and providing abundant nucleation sites. The superior conductivity of the cathode is inherited from two conductive polymers (in particular, PEDOT:PSS fibers have an ultrahigh conductivity of 3676 S cm−1) and their strong intermolecular interactions. The resulting FZMB shows excellent stability (over 100% capacity retention after 3000 cycles) and supercapacitor‐level rate performance (73% capacity retention from 0.1 to 10 A g−1). Kinetics and mechanism studies reveal that the surface‐controlled dual‐ion migration mechanism is also correlated with the high rate performance. The corresponding quasi‐solid‐state device exhibits high stability under extreme deformation conditions and superior water‐proof capability (94.6% capacity retention after 12 h underwater immersion), demonstrating great practical application potential.
A dendrite‐free and durable fiber anode is developed by engineering a functional interface via nano‐thin conductive carbon sputtering. Also, an ultraconductive fiber cathode is fabricated via a dual‐conductive polymer strategy. Based on the dedicatedly designed electrodes, the first fiber zinc dual‐ion microbattery is demonstrated. It delivers superior electrochemical performance, mechanical flexibility, and water‐proof capability, indicating vast practical application potential.
The application of graphene‐based membranes is hindered by their poor stability under practical hydrodynamic conditions. Here, nanocarbon architectures are designed by intercalating ...surface‐functionalized, small‐diameter, multi‐walled carbon nanotubes (MWCNTs) into reduced graphene oxide (rGO) sheets to create highly stable membranes with improved water permeability and enhanced membrane selectivity. With the intercalation of 10 nm diameter MWCNTs, the water permeability reaches 52.7 L m−2 h−1 bar−1, which is 4.8 times that of pristine rGO membrane and five to ten times higher than most commercial nanofiltration membranes. The membrane also attains almost 100% rejection for three organic dyes of different charges. More importantly, the membrane can endure a turbulent hydrodynamic flow with cross‐flow rates up to 2000 mL min−1 and a Reynolds number of 4667. Physicochemical characterization reveals that the inner graphitic walls of the MWCNTs can serve as spacers, while nanoscale rGO foliates on the outer walls interconnect with the assimilated rGO sheets to instill superior membrane stability. In contrast, intercalating with single‐walled nanotubes fails to reproduce such stability. Overall, this nanoarchitectured design is highly versatile in creating both graphene‐rich and CNT‐rich all‐carbon membranes with engineered nanochannels, and is regarded as a general approach in obtaining stable membranes for realizing practical applications of graphene‐based membranes.
All‐carbon nanoarchitectured membranes comprising reduced graphene oxide and multi‐walled carbon nanotubes exhibit a high water permeability, which is five to ten times higher than most commercial nanofiltration membranes. The membranes show almost 100% organic dye rejection and, most importantly, superior membrane stability under a turbulent hydrodynamic flow condition of 2000 mL min−1 and a Reynolds number of 4667.
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