Graphene‐Based Organic Electrochemical Capacitors for AC Line Filtering

Less‐defective graphene oxide sheets with a small average size of 0.7 µm are electrochemically reduced to form a hydrogel film with highly oriented porous structure. It is applied as the electrode of organic electrochemical capacitor (OEC) after solvent change with organic electrolyte and deep reduction in this organic medium. At 120 Hz, the typical OEC exhibits a high areal specific energy density of 472 µF V² cm^?2 with a wide workable voltage window of 2.5 V, a phase angle of ?80.5°, a resistor‐capacitor time constant (τ_RC) of 0.219 ms, and an excellent electrochemical stability. Thus, it is promising to replace aluminum electrolytic capacitors for AC line filtering. Furthermore, two identical OECs connected in series keep the performance of single device, making them practically applicable in electronics.     

Hierarchical Carbide‐Derived Carbon Foams with Advanced Mesostructure as a Versatile Electrochemical Energy‐Storage Material

Highly porous carbide‐derived carbon (CDC) mesofoams (DUT‐70) are prepared by nanocasting of mesocellular silica foams with a polycarbosilane precursor. Ceramic conversion followed by silica removal and high‐temperature chlorine treatment yields CDCs with a hierarchical micro‐mesopore arrangement. This new type of polymer‐based CDC is characterized by specific surface areas as high as 2700 m² g^?1, coupled with ultrahigh micro‐ and mesopore volumes up to 2.6 cm³ g^?1. The relationship between synthesis conditions and the properties of the resulting carbon materials is described in detail, allowing precise control of the properties of DUT‐70. Since the hierarchical pore system ensures both efficient mass transfer and high capacities, the novel CDC shows outstanding performance as an electrode material in electrochemical double‐layer capacitors (EDLCs) with specific capacities above 240 F g^?1 when measured in a symmetrical two‐electrode configuration. Remarkable capacities of 175 F g^?1 can be retained even at high current densities of 20 A g^?1 as a result of the enhanced ion‐transport pathways provided by the cellular mesostructure. Moreover, DUT‐70 can be infiltrated with sulfur and host the active material in lithium–sulfur battery cathodes. Reversible capacities of 790 mAh g^?1 are achieved at a current rate of C/10 after 100 cycles, which renders DUT‐70 an ideal support material for electrochemical energy‐storage applications.     

Strain‐Based In Situ Study of Anion and Cation Insertion into Porous Carbon Electrodes with Different Pore Sizes

The expansion of porous carbon electrodes in a room temperature ionic liquid (RTIL) is studied using in situ atomic force microscopy (AFM). The effect of carbon surface area and pore size/pore size distribution on the observed strain profile and ion kinetics is examined. Additionally, the influence of the potential scan rate on the strain response is investigated. By analyzing the strain data at various potential scan rates, information on ion kinetics in the different carbon materials is obtained. Molecular dynamics (MD) simulations are performed to compare with and provide molecular insights into the experimental results; this is the first MD work investigating the pressure exerted on porous electrodes under applied potential in a RTIL electrolyte. Using MD, the pressure exerted on the pore wall is calculated as a function of potential/charge for both a micropore (1.2 nm) and a mesopore (7.0 nm). The shape of the calculated pressure profile matches closely with the strain profiles observed experimentally.     

MOF‐Based Transparent Passivation Layer Modified ZnO Nanorod Arrays for Enhanced Photo‐Electrochemical Water Splitting

This study introduces zeolitic imidazolate framework‐8 (ZIF‐8) as the first metal‐organic framework based transparent surface passivation layer for photo‐electrochemical (PEC) water splitting. A significant enhancement for PEC water oxidation is demonstrated based on the in situ seamless coating of ZIF‐8 surface passivation layer on Ni foam (NF) supported ZnO nanorod arrays photoanode. The PEC performance is improved by optimizing the ZIF‐8 thickness and by grafting Ni(OH)₂ nanosheets as synergetic co‐catalyst. With respect to ZnO/NF, the optimized Ni(OH)₂/ZIF‐8/ZnO/NF photoanode exhibits a two times larger photocurrent density of 1.95 mA cm^?2 and also a two times larger incident photon to current conversion efficiency of 40.05% (350 nm) at 1.23 V versus RHE (V_RHE) under AM 1.5 G. The synergetic surface passivation and the co‐catalyst modification contribute to prolonging the charge lifetime, to promoting the charge transfer, and to decreasing the overpotential for water oxidation.     

Rational Construction of Nitrogen‐Doped Hierarchical Dual‐Carbon for Advanced Potassium‐Ion Hybrid Capacitors

Potassium‐ion hybrid capacitors (PIHCs), elaborately integrate the advantages of high output power as well as long lifespan of supercapacitors and the high energy density of batteries, and exhibit great possibilities for the future generations of energy storage devices. The critical next step for future implementation lies in exploring a high‐rate battery‐type anode with an ultra‐stable structure to match the capacitor‐type cathode. Herein, a “dual‐carbon” is constructed, in which a three‐dimensional nitrogen‐doped microporous carbon polyhedron (NMCP) derived from metal‐organic frameworks is tightly wrapped by two‐dimensional reduced graphene oxide (NMCP@rGO). Benefiting from the synergistic effect of the inner NMCP and outer rGO, the NMCP@rGO exhibits a superior K‐ion storage capability with a high reversible capacity of 386 mAh g^?1 at 0.05 A g^?1 and ultra‐long cycle stability with a capacity of 151.4 mAh g^?1 after 6000 cycles at 5.0 A g^?1. As expected, the as‐assembled PIHCs with a working voltage as high as 4.2 V present a high energy/power density (63.6 Wh kg^?1 at 19 091 W kg^?1) and excellent capacity retention of 84.7% after 12 000 cycles. This rational construction of advanced PIHCs with excellent performance opens a new avenue for further application and development.     

Dual‐Confined Flexible Sulfur Cathodes Encapsulated in Nitrogen‐Doped Double‐Shelled Hollow Carbon Spheres and Wrapped with Graphene for Li–S Batteries

Batteries with high energy and power densities along with long cycle life and acceptable safety at an affordable cost are critical for large‐scale applications such as electric vehicles and smart grids, but is challenging. Lithium–sulfur (Li‐S) batteries are attractive in this regard due to their high energy density and the abundance of sulfur, but several hurdles such as poor cycle life and inferior sulfur utilization need to be overcome for them to be commercially viable. Li–S cells with high capacity and long cycle life with a dual‐confined flexible cathode configuration by encapsulating sulfur in nitrogen‐doped double‐shelled hollow carbon spheres followed by graphene wrapping are presented here. Sulfur/polysulfides are effectively immobilized in the cathode through physical confinement by the hollow spheres with porous shells and graphene wrapping as well as chemical binding between heteronitrogen atoms and polysulfides. This rationally designed free‐standing nanostructured sulfur cathode provides a well‐built 3D carbon conductive network without requiring binders, enabling a high initial discharge capacity of 1360 mA h g^?1 at a current rate of C/5, excellent rate capability of 600 mA h g^?1 at 2 C rate, and sustainable cycling stability for 200 cycles with nearly 100% Coulombic efficiency, suggesting its great promise for advanced Li–S batteries.     

Tunable and Efficient Tin Modified Nitrogen‐Doped Carbon Nanofibers for Electrochemical Reduction of Aqueous Carbon Dioxide

Efficient and selective earth‐abundant catalysts are highly desirable to drive the electrochemical conversion of CO₂ into value‐added chemicals. In this work, a low‐cost Sn modified N‐doped carbon nanofiber hybrid catalyst is developed for switchable CO₂ electroreduction in aqueous medium via a straightforward electrospinning technique coupled with a pyrolysis process. The electrocatalytic performance can be tuned by the structure of Sn species on the N‐doped carbon nanofibers. Sn nanoparticles drive efficient formate formation with a high current density of 11 mA cm^?2 and a faradaic efficiency of 62% at a moderate overpotential of 690 mV. Atomically dispersed Sn species promote conversion of CO₂ to CO with a high faradaic efficiency of 91% at a low overpotential of 490 mV. The interaction between Sn species and pyridinic‐N may play an important role in tuning the catalytic activity and selectivity of these two materials.     

Metal‐Organic Framework Cathodes Based on a Vanadium Hexacyanoferrate Prussian Blue Analogue for High‐Performance Aqueous Rechargeable Batteries

Despite the unique advantages of the metal‐organic framework of Prussian blue analogues (PBAs), including a favorable crystallographic structure and facile diffusion kinetics, the capacity of PBAs delivered in aqueous systems has been limited to ≈60 mA h g^?1 because only single species of transition metal ions incorporated into the PBAs are electrochemically activated. Herein, vanadium hexacyanoferrate (V/Fe PBA) is proposed as a breakthrough to this limitation, and its electrochemical performance as a cathode for aqueous rechargeable batteries (ARBs) is investigated for the first time. V/Fe PBAs are synthesized by a simple co‐precipitation method with optimization of the acidity and molar ratios of precursor solutions. The V/Fe PBAs provide an improved capacity of 91 mA h^?1 under a current density of 110 mA g^?1 (C‐rate of ≈1.2 C), taking advantage of the multiple‐electron redox reactions of V and Fe ions. Under an extremely fast charge/discharge rate of 3520 mA g^?1, the V/Fe PBA exhibits a sufficiently high discharge capacity of 54 mA h g^?1 due to its opened structure and 3D hydrogen bonding networks. V/Fe PBA‐based ARBs are the most promising candidates for large‐scale stationary energy storage systems due to their high electrochemical performance, reasonable cost, and high efficiency.     

A Cross‐Linked Interconnecting Layer Enabling Reliable and Reproducible Solution‐Processing of Organic Tandem Solar Cells

The performance of tandem organic solar cells (OSCs) is directly related to the functionality and reliability of the interconnecting layer (ICL). However, it is a challenge to develop a fully functional ICL for reliable and reproducible fabrication of solution‐processed tandem OSCs with minimized optical and electrical losses, in particular for being compatible with various state‐of‐the‐art photoactive materials. Although various ICLs have been developed to realize tandem OSCs with impressively high performance, their reliability, reproducibility, and generic applicability are rarely analyzed and reported so far, which restricts the progress and widespread adoption of tandem OSCs. In this work, a robust and fully functional ICL is developed by incorporating a hydrolyzed silane crosslinker, (3‐glycidyloxypropyl)trimethoxysilane (GOPS), into poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), and its functionality for reliable and reproducible fabrication of tandem OSCs based on various photoactive materials is validated. The cross‐linked ICL can successfully protect the bottom active layer against penetration of high boiling point solvents during device fabrication, which widely broadens the solvent selection for processing photoactive materials with high quality and reliability, providing a great opportunity to continuously develop the tandem OSCs towards future large‐scale production and commercialization.     

Metal‐Organic Frameworks for Carbon Dioxide Capture and Methane Storage

In the global transition to a sustainable low‐carbon economy, CO₂ capture and storage technology still plays a critical role for deep emission reduction, particularly for the stationary sources in power generation and industry. However, for small and mobile emission sources in transportation, CO₂ capture is not suitable and it is more practical to use relatively clean energy, such as natural gas. In these two low‐carbon energy technologies, designing highly selective sorbents is one of the key and most challenging steps. Toward this end, metal‐organic frameworks (MOFs) have received continuously intensive attention in the past decades for their highly porous and diversified structures. In this review, the recent progress in developing MOFs for selective CO₂ capture from post‐combustion flue gas and CH₄ storage for vehicle applications are summarized. For CO₂ capture, several promising strategies being used to improve CO₂ adsorption uptake at low pressures are highlighted and compared. In addition, the conventional and novel regeneration techniques for MOFs are also discussed. In the case of CH₄ storage, the flexible and rigid MOFs, whose CH₄ storage capacity is close to the target set by U.S. Department of Energy are particularly emphasized. Finally, the challenge of using MOFs for CH₄ storage is discussed.     

Single‐Step Spray Printing of Symmetric All‐Organic Solid‐State Batteries Based on Porous Textile Dye Electrodes

A symmetric solid‐state battery based on organic porous electrodes is fabricated using scalable spray‐printing. The active electrode material is based on a textile dye (disperse blue 134 anthraquinone) and is capable of forming divalent cations and anions in oxidation and reduction processes. The resulting molecule can be used in both negative and positive electrode reactions. After spray printing an inter‐connected pore honeycomb electrode, a solid‐state electrolyte (σ_Li: × 10^?4 S cm^?1) based on a polymeric ionic liquid is spray‐printed as a second layer and infiltrated through the porous electrodes. A symmetric all‐organic battery is then formed with the addition of another identical set of electrode and electrolyte layers. Both density functional theory calculations and charge‐discharge profiles show that the potentials for the negative and positive electrode reactions are amongst the lowest (≈2.0 V vs Li) and the highest (≈3.5 V vs Li), respectively, for quinone‐type molecules. Over the C‐rate range 0.2 to 5 C, the battery has a discharge cell voltage of more than 1 V even up to 250 charge‐discharge cycles and capacities are in the range 50–80 mA h g^?1 at 0.5 C.     

荒漠草原典型植物群落土壤活性有机碳组分特征及其与酶活性的关系

以宁夏荒漠草原典型植物柠条(Caragana korshinskii)、沙蒿(Artemisia ordosica)、短花针茅(Stipa breviflora)和蒙古冰草(Agropyron mongolicum)群落为研究对象,分析不同植物群落不同土层深度(0~5、5~10和10~15cm)土壤活性有机碳组分土壤微生物量碳(MBC)、可溶性有机碳(DOC)和易氧化有机碳(EOC)特征及其与土壤酶(蔗糖酶、脲酶、碱性磷酸酶和过氧化氢酶)活性之间的关系。结果表明:(1)4种典型植物群落土壤SOC、MBC、EOC含量均随土层深度的增加而减少,且表层(0~5cm)土壤显著高于亚表层(5~10cm)和深层(10~15cm)土壤(P0.05),而土壤DOC含量随土层深度的增加呈先增加后减少的趋势。在同一土层深度,灌木(柠条和沙蒿)群落土壤活性有机碳组分含量高于禾本科植物(短花针茅和蒙古冰草)。(2)4种典型植物群落土壤酶(蔗糖酶、脲酶、磷酸酶和过氧化氢酶)活性整体上随土层深度的增加而降低,局部土层深度表现出波动性;同一土层不同植被群落土壤酶活性未表现出一定的变化规律。(3)4种典型群落土壤活性有机碳各组分除DOC外,其余均与SOC呈显著正相关关系,与土壤酶活性、微生物量熵以及有机碳活度具有一定的相关关系,表明土壤活性有机碳不仅依赖于总有机碳,也与土壤酶活性密切相关。     

NiFe‐Based Metal–Organic Framework Nanosheets Directly Supported on Nickel Foam Acting as Robust Electrodes for Electrochemical Oxygen Evolution Reaction

It is of great significance to develop highly efficient and superior stable oxygen evolution reaction (OER) electrocatalysts for upcoming electrochemical conversion technologies and clean energy systems. Here, an assembled 3D electrode is synthesized by a one‐step solvothermal process using such an original OER electrocatalyst. During the solvothermal process, Ni ions released from Ni foam in acidic solution and Fe ions added exogenously act as metal centers and coordinate with terephthalic acid (TPA) organic molecules by robust coordinate bonds, and finally, NiFe‐based metal–organic framework (MOF) nanosheets in situ grown on Ni foam, i.e., MIL‐53(FeNi)/NF, are prepared. This binder‐free 3D electrode shows superior OER activity with high current density (50 mA cm^?2) at an overpotential of 233 mV, a Tafel slope of 31.3 mV dec^?1, and excellent stability in alkaline aqueous solution (1 m KOH). It is discovered that introduction of Fe into MIL‐53 structure increases electrochemically‐active areas as well as reaction sites, accelerated electron transport capability, and modulated electronic structure to enhance catalytic performance. Besides, first principles calculations show that MIL‐53(FeNi) is more favorable for foreign atoms' adsorption and has increased 3d orbital electron density boosting intrinsic activity. This work elucidates a promising electrode for electrocatalysts and enriches direct application of MOF materials.     

All‐Organic Battery Composed of Thianthrene‐ and TCAQ‐Based Polymers

An all‐organic battery consisting of two redox‐polymers, namely poly(2‐vinylthianthrene) and poly(2‐methacrylamide‐TCAQ) is assembled. This all‐organic battery shows excellent performance characteristics, namely flat discharge plateaus, an output voltage exceeding 1.3 V, and theoretical capacities of both electrodes higher than 100 mA h g^?1. Both organic electrode materials are synthesized in two respective three synthetic steps using the free‐radical polymerization technique. Li‐organic batteries manufactured from these polymers prove their suitability as organic electrode materials. The cathode material poly(2‐vinylthianthrene) (3) displays a discharging plateau at 3.95 V versus Li⁺/Li and a discharge capacity of 105 mA h g^?1, corresponding to a specific energy of about 415 mW h g^?1. The anode material poly(2‐methacrylamide‐TCAQ) (7) exhibits an initial discharge capacity of 130 mA h g^?1, corresponding to 94% material activity. The combination of both materials results in an all‐organic battery with a discharge voltage of 1.35 V and an initial discharge capacity of 105 mA h g^?1 (95% material activity).     

Spontaneous Growth of 3D Framework Carbon from Sodium Citrate for High Energy‐ and Power‐Density and Long‐Life Sodium‐Ion Hybrid Capacitors

Carbon sheets with 3D architectures, large graphitic interlayer spacing, and high electrical conductivity are highly expected to be an ideal anode material for sodium‐ion hybrid capacitors (SIHCs). Pursuing a simple synthesis methodology and advancing it from the laboratory to industry is of great importance. In this study, a new approach is presented to prepare 3D framework carbon (3DFC) with the above integrated advantages by a direct calcination of sodium citrate without aid of any additional carbon source, template, or catalyst. The first‐principle calculations verify that the large interlayer spacing and the curvature structure of 3DFC facilitate the sodium ion insertion/extraction. As a consequence, the optimal 3DFC sample exhibits high reversible capacity as well as excellent rate and cycling performance. On this basis, a dual‐carbon SIHC is fabricated by employing 3DFC as battery‐type anode and 3DFC‐derived nanoporous carbon as capacitor‐type cathode. It is able to deliver high energy‐ and power‐density feature as well as outstanding long‐term cycling stability in the potential range of 0–4.0 V. This study may open an avenue for developing high‐performance carbon electrode materials and pushes the practical applications of SIHCs a decisive step forward.