High-Efficiency Electroreduction of Nitrite to Ammonia on Ni Nanoparticles Strutted 3D Honeycomb-Like Porous Carbon Framework

Electroreduction of nitrite (NO2 - ) to ammonia (NH3 ) provides a sustainable approach to yield NH3 , whilst eliminating NO2 - contaminants. In this study, Ni nanoparticles strutted 3D honeycomb-like porous carbon framework (Ni@HPCF) is fabricated as a high-efficiency electrocatalyst for selective reduction of NO2 - to NH3 . In 0.1 M NaOH with NO2 - , such Ni@HPCF electrode obtains a significant NH3 yield of 12.04 mg h-1  mgcat. -1 and a Faradaic efficiency of 95.1 %. Furthermore, it exhibits good long-term electrolysis stability.

Enhancing quorum quenching media with 3D robust electrospinning coating: A novel biofouling control strategy for membrane bioreactors

Bacterial quorum quenching (QQ) is an effective strategy for controlling biofouling in membrane bioreactor (MBR) by interfering the releasing and degradation of signal molecules during quorum sensing (QS) process. However, due to the framework feature of QQ media, the maintenance of QQ activity and the restriction of mass transfer threshold, it has been difficult to design a more stable and better performing structure in a long period of time. In this research, electrospun fiber coated hydrogel QQ beads (QQ-ECHB) were fabricated by using electrospun nanofiber coated hydrogel to strengthen layers of QQ carriers for the first time. The robust porous PVDF 3D nanofiber membrane was coated on the surface of millimeter-scale QQ hydrogel beads. Biocompatible hydrogel entrapping quorum quenching bacteria (sp.BH4) was employed as the core of the QQ-ECHB. In MBR with the addition of QQ-ECHB, the time to reach transmembrane pressure (TMP) of 40 kPa was 4 times longer than conventional MBR. The robust coating and porous microstructure of QQ-ECHB contributed to keeping a lasting QQ activity and stable physical washing effect at a very low dosage (10g beads/5L MBR). Physical stability and environmental-tolerance tests also verified that the carrier can maintain the structural strength and keep the core bacteria stable when suffering long-term cyclic compression and great fluctuations in sewage quality.

Achieving Electronic Engineering of Vanadium Oxide-Based 3D Lithiophilic Sandwiched-Aerogel Framework for Ultrastable Lithium Metal Batteries

Lithium (Li) metal is one of the most promising anode materials for the next-generation batteries, which owns superior specific capacity and energy density. Unfortunately, lithium dendrites that is formed during the charging/discharging process tends to induce capacity degradation and thus short lifespan. In this study, the vanadium oxide (V2O5) and nitrogen-doped vanadium oxide (N-V2O3, N-VO0.9)-modified three-dimensional (3D) reduced graphene oxide ((N)-VOx@rGO) with tunable electronic properties are demonstrated to enable the dendrite-free Li deposition. The soft lithiophilic rGO as the scaffold can provide sufficient void space for Li storage. Meanwhile, the rigid (N)-VOx uniformly anchored on rGO can perfectly maintain the 3D structure, which is crucial for Li to enter the inner space of the 3D framework. Consequently, the (N)-VOx@rGO electrodes achieve dendrite-free electrodeposition under the multifarious deposition capacity and current densities. Compared with the bare lithium electrodes, the asymmetrical cells of (N)-VOx@rGO anode can cycle stably up to 400 h at 2 mA cm-2 current density, together with a low nucleation overpotential of ∼20 mV.

Synergistic Effect of 3D Flexible Framework with Sodiophilic Mesoporous SnO2 Nanosheet Arrays on Dendrite-Free Sodium Metal Batteries

Although tremendous efforts have been dedicated to promote the electrochemical stability of sodium metal batteries (SMBs), the uncontrollable dendrites growth and inevitable side reactions at the sodium (Na) anode/electrolyte interface have not been effectively resolved. In this work, a flexible and functionalized 3D framework with mesoporous SnO₂ nanosheet arrays (SnO₂@CC-12) is fabricated to serve as a sodiophilic matrix toward dendrite-free Na metal anode. The mesoporous SnO₂ nanosheet arrays provide abundant sodiophilic sites and sufficient internal voids, which can not only accelerate electron transport to reduce the local current density of Na anode surface but also manipulate the Na⁺ flux deposition to suppress the growth of Na dendrites. Therefore, the SnO₂@CC-12-Na symmetric cell exhibits an ultralow overpotential of 9 mV and superior Na plating/stripping stability over 2200 h at 1.0 mA cm^-2. Moreover, the full cells using Na₃V₂(PO₄)₃ cathode show favorable high-rate performance and impressive long cycling stability with 95.1% capacity retention over 1000 cycles at 500 mA g^-1. This work may provide a new insight into the design of functionalized interface layer with high sodiophilicity toward dendrite-free SMBs.

How Is Cycle Life of Three-Dimensional Zinc Metal Anodes with Carbon Fiber Backbones Affected by Depth of Discharge and Current Density in Zinc-Ion Batteries?

Zinc (Zn) metal is an attractive anode material for aqueous Zn-ion batteries (ZIBs). Three-dimensional (3D) carbon frameworks may serve as lightweight and robust hosts to enable porous Zn electrodes with a long cycle life. However, Zn electrode tests under a low depth of discharge (DOD) and current density often yield unreliable promises. We used 3D Zn electrodes with carbon nanofiber framework (CNF) backbones (Zn@CNF) as model electrodes to reveal how DOD and current density affect their performance. Plasma-treated CNFs provide sufficient surface hydrophilicity and surface area to allow uniform Zn plating/stripping of a thin and uniform Zn coating (5 mAh cm^-2). CNFs only take a small weight fraction (17.5-19.7 wt. %) in the composite electrodes. The 3D structure and graphitic surface efficiently suppress dendrite growth. The cycle life of Zn@CNF can reach 843 h under 10% DOD and 0.5 mA cm^-2 in symmetric cells. However, high DOD and current density are detrimental to the stability of 3D Zn electrodes. The cycle life drops to 60.75 h under 60% DOD and 4 mA cm^-2. Full cells assembled using Zn@CNF as anodes and V₂O₅ as cathodes with an N/P capacity ratio of 2.4 delivered a capacity of 133.4 mAh g^-1 at 0.1 A g^-1. The full cells also showed excellent capacity retention of 92.1% after 260 cycles under 0.5 A g^-1 with a high average DOD_Zn of 15.5%. Our results suggest that 3D Zn electrodes with CNF backbones are promising anodes for ZIBs. Studying Zn metal electrodes under practical DOD and current density is essential to access their potential accurately.

Critical assessment of the performance of next-generation carbon-based adsorbents for CO2 capture focused on their structural properties

Carbon dioxide emissions and their sharply rising effect on global warming have encouraged research efforts to develop efficient technologies and materials for CO₂ capture. Post-combustion CO₂ capture by adsorption using solid materials is considered an attractive technology to achieve this goal. Templated materials, such as Zeolite Templated-Carbons and MOF-Derived Carbons, are considered as the next-generation carbon adsorbent materials, owing to their outstanding textural properties (high surface areas of ca. 4000 m² g^-1 and micropore volumes of ca. 1.7 cm³ g^-1) and their versatility for surface functionalization. These materials have demonstrated remarkable CO₂ adsorption capacities and CO₂/N₂ selectivities up to ca. 5 mmol g^-1 and 100, respectively, at 298 K and 1 bar, and low isosteric heat of adsorption at zero coverage of ca. 12 kJ mol^-1. Herein, a review of the advances in preparation of ZTCs and MDCs for CO₂ capture is presented, followed by a critical analysis of the effects of textural properties and surface functionality on CO₂ adsorption, including CO₂ uptake, CO₂/N₂ selectivity, and isosteric heat of adsorption. This analysis led to the introduction of a V_microx N-content factor to evaluate the interplay between N-content and textural properties to maximize the CO₂ uptake. Despite their promising performance in CO₂ uptake, further testing using mixtures and impurities, and studies on adsorbent regeneration, and cyclic operation are desirable to demonstrate the stability of the MDCs and ZTCs for large scale processes. In addition, advances in scale-up syntheses and their economics are needed.

Real-Time 3D Framework Tracing of Extracellular Polymeric Substances by an AIE-Active Nanoprobe

Extracellular polymeric substances (EPS) are produced by many microorganisms and play an essential role in physiological systems such as nutrient storage and stress resistance. Besides, EPS show great potential in biomedical and therapeutic applications due to their biocompatibility and biodegradability. In situ noninvasive monitoring of the EPS produced by microorganisms is thus critical but has not yet been achieved. Herein, we developed a novel aggregation-induced emission (AIE) active nanoprobe enabling in situ visualization of the EPS distribution produced by various microorganisms (cyanobacteria, yeast, freshwater, and marine phytoplankton). The synthesized AIE-active nanoprobe displayed excellent specificity and precision for the staining of EPS, as well as strong photostability, showing great advantage in sensing the EPS in living organisms. With the application of this novel probe, the three-dimensional (3D) framework of EPS distribution was visualized under different environmental conditions (temperature, light intensity, nutrition, and pH). The EPS distribution was found to correlate significantly with the metal tolerance and cyanobacterial photosynthesis capability. Collectively, this study proposed an AIE-active nanoprobe for visualizing the EPS distribution and quantifying the EPS thickness/volume, and has significant implications in understanding the physiological functions of microorganisms.

Atomic Modulation of 3D Conductive Frameworks Boost Performance of MnO2 for Coaxial Fiber-Shaped Supercapacitors

Coaxial fiber-shaped supercapacitors are a promising class of energy storage devices requiring high performance for flexible and miniature electronic devices. Yet, they are still struggling from inferior energy density, which comes from the limited choices in materials and structure used. Here, Zn-doped CuO nanowires were designed as 3D framework for aligned distributing high mass loading of MnO₂ nanosheets. Zn could be introduced into the CuO crystal lattice to tune the covalency character and thus improve charge transport. The Zn-CuO@MnO₂ as positive electrode obtained superior performance without sacrificing its areal and gravimetric capacitances with the increasing of mass loading of MnO₂ due to 3D Zn-CuO framework enabling efficient electron transport. A novel category of free-standing asymmetric coaxial fiber-shaped supercapacitor based on Zn_0.11CuO@MnO₂ core electrode possesses superior specific capacitance and enhanced cell potential window. This asymmetric coaxial structure provides superior performance including higher capacity and better stability under deformation because of sufficient contact between the electrodes and electrolyte. Based on these advantages, the as-prepared asymmetric coaxial fiber-shaped supercapacitor exhibits a high specific capacitance of 296.6 mF cm^-2 and energy density of 133.47 μWh cm^-2. In addition, its capacitance retention reaches 76.57% after bending 10,000 times, which demonstrates as-prepared device's excellent flexibility and long-term cycling stability.

Simultaneously Regulating the Ion Distribution and Electric Field to Achieve Dendrite-Free Zn Anode

Rechargeable aqueous Zn-ion batteries are promising candidates for large-scale energy storage systems. However, there are many unresolved problems in commercial Zn foils such as dendrite growth and structural collapse. Herein, Cu mesh modified with CuO nanowires is constructed to simultaneously coordinate the ion distribution and electric field during Zn nucleation and growth. Owing to the improved uniformity of Zn plating and the confined Zn growth in the 3D framework, the prepared Zn anodes can be operated steadily in symmetrical cells for 340 h with a low voltage hysteresis (20 mV). This work can provide a new strategy to design the dendrite-free Zn anodes for practical application.

3D Flexible, Conductive, and Recyclable Ti3C2Tx MXene-Melamine Foam for High-Areal-Capacity and Long-Lifetime Alkali-Metal Anode

Alkali metals are ideal anodes for high-energy-density rechargeable batteries, while seriously hampered by limited cycle life and low areal capacities. To this end, rationally designed frameworks for dendrite-free and volume-changeless alkali-metal deposition at both high current densities and capacities are urgently required. Herein, a general 3D conductive Ti₃C₂T_X MXene-melamine foam (MXene-MF) is demonstrated as an elastic scaffold for dendrite-free, high-areal-capacity alkali anodes (Li, Na, K). Owing to the lithiophilic nature of F-terminated MXene, conductive macroporous network, and excellent mechanical toughness, the constructed MXene-MF synchronously achieves a high current density of 50 mA cm^-2 for Li plating, high areal capacity (50 mAh cm^-2) with high Coulombic efficiency (99%), and long lifetime (3800 h), surpassing the Li anodes reported recently. Meanwhile, MXene-MF shows flat voltage profiles for 720 h at 10 mA cm^-2 for the Na anode and 800 h at 5 mA cm^-2 for the K anode, indicative of the wide applicability. Notably, the high current density of 20 mA cm^-2 for 20 mAh cm^-2 for the Na anode, accompanying good recyclability was rarely achieved before. When coupled with sulfur or Na₃V₂(PO₄)₃ cathodes, the assembled MXene-MF alkali (Li, Na)-based full batteries showcase enhanced rate capability and cycling stability, demonstrating the potential of MXene-MF for advanced alkali-metal batteries.

Stable Lithium Metal Anode Enabled by a Lithiophilic and Electron/Ion Conductive Framework

Li metal anode has been considered as the ideal anode for next-generation batteries due to its ultrahigh capacity and lowest electrochemical potential. However, its practical application is still impeded by low Coulombic efficiency, huge volume change, and safety hazards arising from Li dendrite growth. In this work, a three-dimensional (3D) structured highly stable Li metal anode is designed and easily preapred. Benefiting from the in situ reaction between Li metal and AlN, highly Li⁺ conductive Li₃N and lithiophilic LiAl alloy have been simultaneously formed and homogeneously distributed in the framework, in which Li metal is finely dispersed and embedded. The outstanding electron/ion mixed conductivity of Li₃N/LiAl and 3D composite structure with enhanced interfacial area significantly improve the electrode kinetics and suppress the volume change on cycling, while a lithiophilic effect of LiAl alloy and uniform distribution of Li ion flux inside the electrode avoid dendritic Li deposition. As a result, the proposed Li metal electrode exhibits exceptional electrochemical reversibility in both carbonate and ether-based electrolytes. Paired with LiFePO₄ and sulfurized polyacrylonitrile (S@pPAN) cathodes, the full cells deliver highly stable and long-term cycling performance. Therefore, the proposed strategy to fabricate Li metal anodes could promote the practical application of Li metal batteries.

Conducting and Lithiophilic MXene/Graphene Framework for High-Capacity, Dendrite-Free Lithium-Metal Anodes

Li-metal anode is widely acknowledged as the ideal anode for high-energy-density batteries, but seriously hindered by the uncontrollable dendrite growth and infinite volume change. Toward this goal, suitable stable scaffolds for dendrite-free Li anodes with large current density (>5 mA cm^-2) and high Li loading (>90%) are highly in demand. Herein, a conductive and lithiophilic three-dimensional (3D) MXene/graphene (MG) framework is demonstrated for a dendrite-free Li-metal anode. Benefiting from its high surface area (259 m² g^-1) and lightweight nature with uniformly dispersed lithiophilic MXene nanosheets as Li nucleation sites, the as-formed 3D MG scaffold showcases an ultrahigh Li content (∼92% of the theoretical capacity), as well as strong capabilities in suppressing the Li-dendrite formation and accommodating the volume changes. Consequently, the MG-based electrode exhibits high Coulombic efficiencies (∼99%) with a record lifespan up to 2700 h and is stable for 230 cycles at an ultrahigh current density of 20 mA cm^-2. When coupled with Li₄Ti₅O₁₂ or sulfur, the MG-Li/Li₄Ti₅O₁₂ full-cell offers an enhanced capacity of 142 mAh g^-1 after 450 cycles, while the MG-Li/sulfur cell delivers an improved rate performance, implying the great potential of this 3D MG framework for building long-lifetime, high-energy-density batteries.

3D Hollow α-MnO2 Framework as an Efficient Electrocatalyst for Lithium-Oxygen Batteries

Lithium-oxygen (Li-O₂ ) batteries are attracting more attention owing to their superior theoretical energy density compared to conventional Li-ion battery systems. With regards to the catalytically electrochemical reaction on a cathode, the electrocatalyst plays a key role in determining the performance of Li-O₂ batteries. Herein, a new 3D hollow α-MnO₂ framework (3D α-MnO₂ ) with porous wall assembled by hierarchical α-MnO₂ nanowires is prepared by a template-induced hydrothermal reaction and subsequent annealing treatment. Such a distinctive structure provides some essential properties for Li-O₂ batteries including the intrinsic high catalytic activity of α-MnO₂ , more catalytic active sites of hierarchical α-MnO₂ nanowires on 3D framework, continuous hollow network and rich porosity for the storage of discharge product aggregations, and oxygen diffusion. As a consequence, 3D α-MnO₂ achieves a high specific capacity of 8583 mA h g^-1 at a current density of 100 mA g^-1 , a superior rate capacity of 6311 mA h g^-1 at 300 mA g^-1 , and a very good cycling stability of 170 cycles at a current density of 200 mA g^-1 with a fixed capacity of 1000 mA h g^-1 . Importantly, the presented design strategy of 3D hollow framework in this work could be extended to other catalytic cathode design for Li-O₂ batteries.

Double-Holey-Heterostructure Frameworks Enable Fast, Stable, and Simultaneous Ultrahigh Gravimetric, Areal, and Volumetric Lithium Storage

Deliberate design of advantageous nanostructures holds great promise for developing high-performance electrode materials for electrochemical energy storage. However, it remains a tremendous challenge to simultaneously gain high gravimetric, areal, and volumetric capacities as well as high rate performance and cyclability to meet practical requirements mainly due to the intractable insufficient ion diffusion and limited active sites for dense electrodes with high areal mass loadings. Herein we report a double-holey-heterostructure framework, in which holey Fe₂O₃ nanosheets (H-Fe₂O₃) are tightly and conformably grown on the holey reduced graphene oxide (H-RGO). This hierarchical nanostructure allows for rapid ion and electron transport and sufficient utilization of active sites throughout a highly compact and thick electrode. Therefore, the free-standing flexible H-Fe₂O₃/H-RGO heterostructure anode can simultaneously deliver ultrahigh gravimetric, areal, and volumetric capacities of 1524 mAh g^-1, 4.72 mAh cm^-2, and 2621 mAh cm^-3, respectively, at 0.2 A g^-1 after 120 cycles, and extraordinary rate performance with a capacity of 487 mAh g^-1 (1.51 mAh cm^-2) at a high current density of 30 A g^-1 (93 mA cm^-2) as well as excellent cycling stability with a capacity retention of 96.3% after 1600 cycles, which has rarely been achieved before.