Free-standing membrane incorporating single-atom catalysts for ultrafast electroreduction of low-concentration nitrate.

The release of wastewaters containing relatively low levels of nitrate (NO3-) results in sufficient contamination to induce harmful algal blooms and to elevate drinking water NO3- concentrations to potentially hazardous levels. In particular, the facile triggering of algal blooms by ultra-low concentrations of NO3- necessitates the development of efficient methods for NO3- destruction. However, promising electrochemical methods suffer from weak mass transport under low reactant concentrations, resulting in long treatment times (on the order of hours) for complete NO3- destruction. In this study, we present flow-through electrofiltration via an electrified membrane incorporating nonprecious metal single-atom catalysts for NO3- reduction activity enhancement and selectivity modification, achieving near-complete removal of ultra-low concentration NO3- (10 mg-N L-1) with a residence time of only a few seconds (10 s). By anchoring Cu single atoms supported on N-doped carbon in a carbon nanotube interwoven framework, we fabricate a free-standing carbonaceous membrane featuring high conductivity, permeability, and flexibility. The membrane achieves over 97% NO3- removal with high N2 selectivity of 86% in a single-pass electrofiltration, which is a significant improvement over flow-by operation (30% NO3- removal with 7% N2 selectivity). This high NO3- reduction performance is attributed to the greater adsorption and transport of nitric oxide under high molecular collision frequency coupled with a balanced supply of atomic hydrogen through H2 dissociation during electrofiltration. Overall, our findings provide a paradigm of applying a flow-through electrified membrane incorporating single-atom catalysts to improve the rate and selectivity of NO3- reduction for efficient water purification.

Mechanical Tester Driven by Surface Tension.

The measurement of in-plane mechanical properties, such as Young's modulus and strength, of thin and stretchable materials has long been a challenge. Existing measurements, including wrinkle instability and nano indentation, are either indirect or destructive, and are inapplicable to meshes or porous materials, while the conventional tension test fails to measure the mechanical properties of nanoscale films. Here, we report a technique to test thin and stretchable films by loading a thin film afloat via differential surface tension and recording its deformation. We have demonstrated the method by measuring the Young's moduli of homogeneous films of soft materials including polydimethylsiloxane and Ecoflex and verified the results with known values. We further measured the strain distributions of meshes, both isotropic and anisotropic, which were otherwise nearly impossible to measure. The method proposed herein is expected to be generally applicable to many material systems that are thin, stretchable, and water-insoluble.

Facile Preparation of High-Performance Free-Standing Micro-Supercapacitors by Optimizing Oxygen Groups on Graphene.

Free-standing micro-supercapacitor (MSC) devices without substrate or current collectors are promising for practical applications. However, it is still difficult to prepare high-performance free-standing MSC devices because of the requirement of optimized active sites, conductivity, ion diffusion, controlled patterns, moisture susceptibility, etc. Here, it is proposed that the optimization of oxygen level on graphene is promising to solve these requirements because of the balance of sp2 and sp3 hybridization. Using the medium-oxidized graphene, the flexible, conductive, hydro-stable, easy-processing film can be facilely obtained, which facilitates the preparation of free-standing MSC electrodes. After constructing with gel electrolyte, the free-standing MSC device shows a high capacitance of 898.4 mF cm-2 using aqueous-gel electrolyte and 383.6 mF cm-2 using ion-gel electrolyte with mass loading of ca. 10 mg cm-2. Correspondingly, the MSC device can achieve a landmark energy density of 42.6 µWh cm-2 at 0.85 mW cm-2 (7.1 mWh cm-3 at 141.7 mW cm-3). The advantages of high performance, facile preparation, and low inactive components make the free-standing MSC device promising for practical applications.

Evidence of the Monopolar-Dipolar Crossover Regime: A Multiscale Study of Ferroelastic Domains by In Situ Microscopy Techniques.

The elastic interaction between kinks (and antikinks) within domain walls plays a pivotal role in shaping the domain structure, and their dynamics. In bulk materials, kinks interact as elastic monopoles, dependent on the distance between walls (d-1) and typically characterized by a rigid and straight domain configuration. In this work the evolution of the domain structure is investigated, as the sample size decreases, by the means of in situ heating microscopy techniques on free-standing samples. As the sample size decreases, a significant transformation is observed: domain walls exhibit pronounced curvature, accompanied by an increase in both domain wall and junction density. This transformation is attributed to the pronounced influence of kinks, inducing sample warping, where "dipole-dipole" interactions are dominant (d-2). Moreover, a critical thickness range that delineates a crossover between the monopolar and dipolar regimens is experimentally identified and corroborated by atomic simulations. These findings are relevant for in situ TEM studies and for the development of novel devices based on free-standing ferroic thin films and nanomaterials.

Ultrafast 2D Nanosheet Assembly via Spontaneous Spreading Phenomenon.

In 2D materials, a key engineering challenge is the mass production of large-area thin films without sacrificing their uniform 2D nature and unique properties. Here, it is demonstrated that a simple fluid phenomenon of water/alcohol solvents can become a sophisticated tool for self-assembly and designing organized structures of 2D nanosheets on a water surface. In situ, surface characterizations show that water/alcohol droplets of 2D nanosheets with cationic surfactants exhibit spontaneous spreading of large uniform monolayers within 10 s. Facile transfer of the monolayers onto solid or flexible substrates results in high-quality mono- and multilayer films with high coverages (>95%) and homogeneous electronic/optical properties. This spontaneous spreading is quite general and can be applied to various 2D nanosheets, including metal oxides, graphene oxide, h-BN, MoS2, and transition metal carbides, enabling on-demand smart manufacture of large-size (>4 inchϕ) 2D nanofilms and free-standing membranes.

Hydrogen-Bonded Metal-Organic Framework Nanosheet as a Proton Conducting Membrane for an H2/O2 Fuel Cell.

Proton-conducting metal-organic frameworks (MOFs) have attracted attention as potential electrolytes for fuel cells. However, research progress in utilizing MOFs as electrolytes for fuel cells has been limited, mainly due to challenges associated with issues such as the fabrication of MOF membranes, and hydrogen crossover through the MOF's pores. Here, proton conductivity and fuel cell performance of a self-standing membrane prepared from of a bismuth subgallate MOF nanosheets with non-porous structure are reported. The fabricated MOF nanosheet membrane with no binding agent exhibits structural anisotropy. The proton conductivity in the membrane thickness direction (4.4 × 10-3 S cm-1) at 90 °C and RH 100% is observed to be higher than that in the in-plane direction of the membrane (3.3 × 10-5 S cm-1). The open circuit voltage (OCV) of a fuel cell with ≈120 µm proton conducting membrane is 1.0 V. The non-porous nature of the MOF nanosheets contributes to the relatively high OCV. A fuel cell using ≈40 µm membrane as proton conducting electrolyte records a maximum of 25 mW cm-2 power density and a maximum of 109 mA cm-2 current density with 0.91 V OCV at 80 °C in humid conditions.

Development of 1D-Metalloid-Induced Highly Porous Carbon Nanofiber Conjugated with PEDOT Polymer Through Concurrent Selenization of ZIF-67 for Energy Storage and Green H2 Production.

Manufacturing high-performance and cost-affordable non-metallic, electroactive 1D carbon material for energy storage and hydrogen evolution reaction (HER) is of foremost importance to respond positively to the impending energy crisis. Porous N-doped carbon nanofiber (PNCNF) is successfully synthesized by electrospinning, using selenium nanoparticles as a sacrificial template (where Se is reutilized for ZIF-67 selenization as a bi-process, and the surface of PNCNF is modified with poly(3,4-ethylenedioxythiophene) (PNCNT/PEDOT) by electropolymerization. The prepared materials are found ideal for energy storage (supercapacitor) and electrocatalysis (HER). The bi-functional material has shown excellent energy storage capability with the specific capacitance (CS) of 230 F g-1 (PNCNF) and 395 F g-1 (PNCNF/PEDOT), and the symmetric supercapacitor device, PNCNF/PEDOT//PEDOT/PNCNF, exhibits 32.4 Wh kg-1 energy density at 14400 W kg-1 power density with 96.6% Coulombic efficiency and 106% CS at the end of 5000 charge-discharge cycles. The rate capability of the symmetric supercapacitor cell of PNCNF/PEDOT is 51% for the current density increase from 1 to 8 A g-1, while that of PNCNF is a meager 29% only. Electrocatalytic HER at the PNCNF electrode is achieved with an overpotential of 281 mV@10 mA cm-2 relative to the Pt/C electrode and a low Tafel slop value of 96 mV dec-1.

Deeper Insights into the Morphology Effect of Na2Ti3O7 Nanoarrays on Sodium-Ion Storage.

Na2Ti3O7-based anodes show great promise for Na+ storage in sodium-ion batteries (SIBs), though the effect of Na2Ti3O7 morphology on battery performance remains poorly understood. Herein, hydrothermal syntheses is used to prepare free-standing Na2Ti3O7 nanosheets or Na2Ti3O7 nanotubes on Ti foil substrates, with the structural and electrochemical properties of the resulting electrodes explored in detail. Results show that the Na2Ti3O7 nanosheet electrode (NTO NSs) delivered superior performance in terms of reversible capacity, rate capability, and especially long-term durability in SIBs compared to its nanotube counterpart (NTO NTs). Electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) investigations, combined with density functional theory calculations, demonstrated that the flexible 2D Na2Ti3O7 nanosheets are mechanically more robust than the rigid Na2Ti3O7 nanotube arrays during prolonged battery cycling, explaining the superior durability of the NTO NSs electrode. This work prompts the use of anodes based on Na2Ti3O7 nanosheets in the future development of high-performance SIBs.

Carbon Fiber Film with Multi-Hollow Channels to Expedite Oxygen Electrocatalytic Reaction Kinetics for Flexible Zn-Air Battery.

The high oxygen electrocatalytic overpotential of flexible cathodes due to sluggish reaction kinetics result in low energy conversion efficiency of wearable zinc-air batteries (ZABs). Herein, lignin, as a 3D flexible carbon-rich macromolecule, is employed for partial replacement of polyacrylonitrile and constructing flexible freestanding air electrodes (FFAEs) with large amount of mesopores and multi-hollow channels via electrospinning combined with annealing strategy. The presence of lignin with disordered structure decreases the graphitization of carbon fibers, increases the structural defects, and optimizes the pore structure, facilitating the enhancement of electron-transfer kinetics. This unique structure effectively improves the accessibility of graphitic-N/pyridinic-N with oxygen reduction reaction (ORR) activity and pyridinic-N with oxygen evolution reaction (OER) activity for FFAEs, accelerating the mass transfer process of oxygen-active species. The resulting N-doped hollow carbon fiber films (NHCFs) exhibit superior bifunctional ORR/OER performance with a low potential difference of only 0.60 V. The rechargeable ZABs with NHCFs as metal-free cathodes possess a long-term cycling stability. Furthermore, the NHCFs can be used as FFAEs for flexible ZABs which have a high specific capacity and good cycling stability under different bending states. This work paves the way to design and produce highly active metal-free bifunctional FFAEs for electrochemical energy devices.

MOF-Derived CoSe2 Nanoparticles/Carbonized Melamine Foam as Catalytic Cathode Enabling Flexible Li-CO2 Batteries with High Energy Efficiency and Stable Cycling.

Rechargeable aprotic Li-CO2 batteries have aroused worldwide interest owing to their environmentally friendly CO2 fixation ability and ultra-high specific energy density. However, its practical applications are impeded by the sluggish reaction kinetics and discharge product accumulation during cycling. Herein, a flexible composite electrode comprising CoSe2 nanoparticles embedded in 3D carbonized melamine foam (CoSe2/CMF) for Li-CO2 batteries is reported. The abundant CoSe2 clusters can not only facilitate CO2 reduction/evolution kinetics but also serve as Li2CO3 nucleation sites for homogeneous discharge product growth. The CoSe2/CMF-based Li-CO2 battery exhibits a large initial discharge capacity as high as 5.62 mAh cm-2 at 0.05 mA cm-2, a remarkably small voltage gap of 0.72 V, and an ultrahigh energy efficiency of 85.9% at 0.01 mA cm-2, surpassing most of the noble metal-based catalysts. Meanwhile, the battery demonstrates excellent cycling stability of 1620 h (162 cycles) at 0.02 mA cm-2 with an average overpotential of 0.98 V and energy efficiency of 85.4%. Theoretical investigations suggest that this outstanding performance is attributed to the suitable CO2/Li adsorption and low Li2CO3 decomposition energy. Moreover, flexible Li-CO2 pouch cell with CoSe2/CMF cathode displays stable power output under different bending deformations, showing promising potential in wearable electronic devices.

Vertical-Channel Cathode Host Enables Rapid Deposition Kinetics toward High-Areal-Capacity Sodium-Chlorine Batteries.

Rechargeable sodium chloride (Na-Cl2) batteries have emerged as promising alternatives for next-generation energy storage due to their superior energy density and sodium abundance. However, their practical applications are hindered by the sluggish chlorine cathode kinetics related to the aggregation of NaCl and its difficult transformation into Cl2. Herein, the study, for the first time from the perspective of electrode level in Na-Cl2 batteries, proposes a free-standing carbon cathode host with customized vertical channels to facilitate the SOCl2 transport and regulate the NaCl deposition. Accordingly, electrode kinetics are significantly enhanced, and the deposited NaCl is distributed evenly across the whole electrode, avoiding the blockage of pores in the carbon host, and facilitating its oxidation to Cl2. With this low-polarization cathode, the Na-Cl2 batteries can deliver a practically high areal capacity approaching 4 mAh cm-2 and a long cycle life of over 170 cycles. This work demonstrates the significance of pore engineering in electrodes for mediating chlorine conversion kinetics in rechargeable alkali-metal-Cl2 batteries.

Effectively coupling of SnSe2nanosheet with N, Se co-doped carbon nanofibers as self-standing anode for lithium-ion batteries.

Tin selenides possess layered structure and high theoretical capacity, which is considered as desirable anode material for lithium-ion batteries. However, its further development is limited by the low intrinsic electrical conductivity and sluggish reaction kinetics. Herein, a well-designed structure of SnSe2nanosheet attached on N, Se co-doped carbon nanofibers (SnSe2@CNFs) is fabricated as self-standing anodes for lithium-ion batteries. The integration of structural engineering and heteroatom doping enables accelerated electrons transfer and rapid ion diffusion for boosting Li+storage performance. Impressively, the flexible SnSe2@CNFs anodes exhibit inspiring capacity of 837.7 mAh g-1after 800 cycles at 1.2 C with coulombic efficiency almost 100% and superior rate performance 419.5 mAh g-1at 2.4 C. The kinetics analysis demonstrates the pseudocapacitive characteristic of SnSe2@CNFs promotes the storage property. This work sheds light on the hierarchical electrode construction towards high-performance energy storage applications.

A Sustainable Free-Standing Triboelectric Nanogenerator Made of Flexible Composite Film for Brake Pattern Recognition in Automobiles.

In recent years, the automotive industry has made significant progress in integrating multifunctional sensors to improve vehicle performance, safety, and efficiency. As the number of integrated sensors keeps increasing, there is a growing interest in alternative energy sources. Specifically, self-powered sensor systems based on energy harvesting are drawing much attention, with a main focus on sustainability and reducing reliance on typical batteries. This paper demonstrates the use of triboelectric nanogenerators (TENGs) in a computer mouse for efficient energy harvesting and in automobile braking systems for safety applications using SrBi2Ta2O9 (SBTO) perovskite, blended PDMS composite operating in free-standing mode with an interdigitated patterned aluminum electrode. This self-powered sensor is capable of distinguishing between normal and abnormal braking patterns using digital signal processing techniques. It is noteworthy that the addition of 15% wt. of the SBTO in PDMS composite-based TENG delivered 13.5 V, 45 nA, and an output power of 0.98 µW. This new combination of energy harvesting and safety applications enables real-time monitoring and predictive maintenance in the automotive industry.

'Bringing forth' skills and knowledge of newly qualified midwives in free-standing birth centres: A hermeneutic phenomenological study.

AIM: To understand and interpret the lived experience of newly qualified midwives (NQMs) as they acquire skills to work in free-standing birth centres (FSBCs), as well as the lived experience of experienced midwives in FSBCs in Germany who work with NQMs. BACKGROUND: In many high-, middle- and low-income countries, the scope of practice of midwives includes autonomous care of labouring women in all settings, including hospitals, home and FSBCs. There has been to date no research detailing the skills acquired when midwives who have trained in hospitals offer care in out-of-hospital settings. METHODS: This study was underpinned by hermeneutic phenomenology. Fifteen NQMs in their orientation period in a FSBC were interviewed three times in their first year. In addition to this, focus groups were conducted in 13 FSBCs. Data were collected between 2021 and 2023. FINDINGS: Using Heidegger's theory of technology as the philosophical underpinning, the results illustrate that the NQMs were facilitated to bring forth competencies to interpret women's unique variations of physiological labour, comprehending when they could enact intervention-free care, when the women necessitated a gentle intervention, and when acceleration of labour or transfer to hospital was necessary. CONCLUSION: NQMs learned to effectively integrate medical knowledge with midwifery skills and knowledge, creating a bridge between the medical and midwifery approaches to care. IMPLICATIONS: This paper showed the positive effects that an orientation and familiarization period with an experienced team of midwives have on the skill development of novice practitioners in FSBCs. IMPACT: The findings of this study will have an impact on training and orientation for nurse-midwives and direct-entry midwives when they begin to practice in out-of-hospital settings after training and working in hospital labour wards. PATIENT AND PUBLIC CONTRIBUTION: This research study has four cooperating partners: MotherHood, Network of Birth Centres, the Association for Quality at Out-of-Hospital Birth and the German Association of Midwifery Science. The cooperating partners met six times in a period of 2 ½ years to hear reports on the preliminary research findings and discuss these from the point of view of each organization. In addition, at each meeting, three midwives from various FSBCs were present to discuss the results and implications. The cooperating partners also helped disseminate study information that facilitated recruitment.

Ultrafast Thermal Shock Synthesis and Porosity Engineering of 3D Hierarchical Cu-Bi Nanofoam Electrodes for Highly Selective Electrochemical CO2 Reduction.

Massive production of practical metal or alloy based electrocatalysts for electrocatalytic CO2 reduction reaction is usually limited by energy-extensive consumption, poor reproducibility, and weak adhesion on electrode substrates. Herein, we report the ultrafast thermal shock synthesis and porosity engineering of free-standing Cu-Bi bimetallic nanofoam electrocatalysts with 3D hierarchical porous structure and easily adjustable compositions. During the thermal shock process, the rapid heating and cooling steps in several seconds result in strong interaction between metal nanopowders to form multiphase nanocrystallines with abundant grain boundaries and metastable CuBi intermetallic phase. The subsequent porosity engineering process via acid etching and electroreduction creates highly porous Cu-Bi structures that can increase electrochemically active surface area and facilitate mass/charge transfer. Among the Cu-Bi nanofoam electrodes with different Cu/Bi ratios, the Cu4Bi nanofoam exhibited the highest formate selectivity with a Faradaic efficiency of 92.4% at -0.9 V (vs reversible hydrogen electrode) and demonstrated excellent operation stability.

Design of Na3MnZr(PO4)3/Carbon Nanofiber Free-Standing Cathodes for Sodium-Ion Batteries with Enhanced Electrochemical Performances through Different Electrospinning Approaches.

The NASICON-structured Na3MnZr(PO4)3 compound is a promising high-voltage cathode material for sodium-ion batteries (SIBs). In this study, an easy and scalable electrospinning approach was used to synthesize self-standing cathodes based on Na3MnZr(PO4)3 loaded into carbon nanofibers (CNFs). Different strategies were applied to load the active material. All the employed characterization techniques (X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), thermal gravimetric analysis (TGA), and Raman spectroscopy) confirmed the successful loading. Compared to an appositely prepared tape-cast electrode, Na3MnZr(PO4)3/CNF self-standing cathodes demonstrated an enhanced specific capacity, especially at high C-rates, thanks to the porous conducive carbon nanofiber matrix. Among the strategies applied to load Na3MnZr(PO4)3 into the CNFs, the electrospinning (vertical setting) of the polymeric solution containing pre-synthesized Na3MnZr(PO4)3 powders resulted effective in obtaining the quantitative loading of the active material and a homogeneous distribution through the sheet thickness. Notably, Na3MnZr(PO4)3 aggregates connected to the CNFs, covered their surface, and were also embedded, as demonstrated by TEM and EDS. Compared to the self-standing cathodes prepared with the horizontal setting or dip-drop coating methods, the vertical binder-free electrode exhibited the highest capacity values of 78.2, 55.7, 38.8, 22.2, 16.2, 12.8, 10.3, 9.0, and 8.5 mAh/g at C-rates of 0.05C, 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, 10C, and 20C, respectively, with complete capacity retention at the end of the measurements. It also exhibited a good cycling life, compared to its tape-cast counterpart: it displayed higher capacity retention at 0.2C and 1C, and, after cycling 1000 cycles at 1C, it could be further cycled at 5C, 10C, and 20C.

One-step Synthesis of Organic Terminal 2D Ti3C2Tx MXene Nanosheets by Etching of Ti3AlC2 in an Organic Lewis Acid Solvent.

The surface and interface chemistry are critical for controlling the properties of two-dimensional transition metal carbides and nitrides (MXenes). Numerous efforts have been devoted to the functionalization of MXenes with small inorganic ligands; however, few etching methods have been reported on the direct bonding of organic groups to MXene surfaces. In this work, we demonstrated an efficient and rapid strategy for the direct synthesis of 2D Ti3C2Tx MXene nanosheets with organic terminal groups in an organic Lewis acid (trifluoromethanesulfonic acid) solvent, without introducing additional intercalations. The dissolution of aluminum and the subsequent in situ introduction of trifluoromethanesulfonic acid resulted in the extraction of Ti3C2Tx MXene (T=CF3SO3 -) (denoted as CF3SO3H-Ti3C2Tx) flakes with sizes reaching 15 µm and high productivity (over 70 %) of monolayers or few layers. More importantly, the large CF3SO3H-Ti3C2Tx MXene nanosheets had high colloidal stability, making them promising as efficient electrocatalysts for the hydrogen evolution reaction.

Ultrathin Free-Standing Porous Aromatic Framework Membranes for Efficient Anion Transport.

Porous aromatic frameworks (PAFs) show promising potential in anionic conduction due to their high stability and customizable functionality. However, the insolubility of most PAFs presents a significant challenge in their processing into membranes and subsequent applications. In this study, continuous PAF membranes with adjustable thickness were successfully created using liquid-solid interfacial polymerization. The rigid backbone and the stable C-C coupling endow PAF membrane with superior chemical and dimensional stabilities over most conventional polymer membranes. Different quaternary ammonium functionalities were anchored to the backbone through flexible alkyl chains with tunable length. The optimal PAF membrane exhibited an OH- conductivity of 356.6 mS ⋅ cm-1 at 80 °C and 98 % relative humidity. Additionally, the PAF membrane exhibited outstanding alkaline stability, retaining 95 % of its OH- conductivity after 1000 hours in 1 M NaOH. To the best of our knowledge, this is the first application of PAF materials in anion exchange membranes, achieving the highest OH- conductivity and exceptional chemical/dimensional stability. This work provides the possibility for the potential of PAF materials in anionic conductive membranes.

Electrochemical Enhancement of Lithium-Ion Diffusion in Polypyrrole-Modified Sulfurized Polyacrylonitrile Nanotubes for Solid-to-Solid Free-Standing Lithium-Sulfur Cathodes.

The energy density of lithium-sulfurized polyacrylonitrile (Li-SPAN) batteries has chronically suffered from low sulfur content. Although a free-standing electrode can significantly reduce noncapacity mass contribution, the slow bulk reaction kinetics still constrain the electrochemical performance. In this regard, a novel electrochemically active additive, polypyrrole (PPy), is introduced to construct PAN nanotubes as a sulfur carrier. This hollow channel greatly facilitates charge transport within the electrode and increases the sulfur content. Both electrochemical tests and simulations show that the SPANPPy-1% cathode possesses a larger lithium-ion diffusion coefficient and a more homogeneous phase interface than the SPAN cathode. Consequently, significantly improved capabilities and rate properties are achieved, as well as decent exportations under high-sulfur-loading or lean-electrolyte conditions. In-situ and semi-situ characterizations are further performed to demonstrate the nucleation growth of lithium sulfide and the evolution of the electrode surface structure. This type of electrochemically active additive provides a well-supported implementation of high-energy-density Li-S batteries.

Sustainable and Scalable Synthesis of 2D Ultrathin Hierarchical Porous Carbon Nanosheets for High-Performance Supercapacitor.

2D carbon nanomaterials such as graphene, carbon nanosheets, and their derivatives, representing the emerging class of advanced multifunctional materials, have gained great research interest because of their extensive applications ranging from electrochemistry to catalysis. However, sustainable and scalable synthesis of 2D carbon nanosheets (CNs) with hierarchical architecture and irregular structure via a green and low-cost strategy remains a great challenge. Herein, prehydrolysis liquor (PHL), an industrial byproduct of the pulping industry, is first employed to synthesize CNs via a simple hydrothermal carbonization technique. After mild activation with NH4 Cl and FeCl3 , the as-prepared activated CNs (A-CN@NFe) display an ultrathin structure (≈3 nm) and a desirable specific surface area (1021 m2 g-1 ) with hierarchical porous structure, which enables it to be both electroactive materials and structural support materials in nanofibrillated cellulose/A-CN@NFe/polypyrrole (NCP) nanocomposite, and thus endowing nanocomposite with impressive capacitance properties of 2546.3 mF cm-2 at 1 mA cm-2 . Furthermore, the resultant all-solid-state symmetric supercapacitor delivers a satisfactory energy storage ability of 90.1 µWh cm-2 at 250.0 µW cm-2 . Thus, this work not only opens a new window for sustainable and scalable synthesis of CNs, but also offers a double profits strategy for energy storage and biorefinery industry.