Interconnected Nanosheets Research Articles

Surface engineering of paper via binary graphene inks for sustainable micro-supercapacitor with innovative architecture

Paper-based micro-supercapacitors (MSCs) are a vital on-chip micro-energy storage component for degradable and implantable electronics that are envisioned as the forerunner of sustainability revolutions. However, an easily-manipulated, macro-assembly proposal and innovative paper architecture to ameliorate the intrinsic topology surface and nonconducting feature remain challenging. In this work, a generalized surface assembly strategy is reported for controllably engineering a graphene-anchored monolithic network for the degradable metal-free paper MSCs. Devoid of insulating auxiliaries and multistep postprocessing (such as cryogenic assistance), the as-engineered paper electrodes essentially consist of unique conductive fiber layer featuring interconnected nanosheets and accumulated functionalized graphene layer based on micron-sized fibers, providing excellent flexibility and anti-aging properties. The multiscale capillary of cellulose fibers and effective space-charge of functionalized graphene ensure fast charge transport. Consequently, the resulting integrated paper MSCs deliver an impressive areal capacitance of 36.5 mF cm−2, high energy density of 3.25 μWh cm−2 and long-term cycling performance (66.4 % retention after 10 000 cycles), surpassing most previously reported paper-based MSCs. The new charge reservoir engineering on paper to fabricate sustainable energy storage system would open a novel available paradigm for the growing demand of portable and degradable electronics.

Deep reconstruction of crystalline-amorphous heterojunction electrocatalysts for efficient and stable water and methanol electrolysis.

During electrocatalytic water splitting, surface reconstruction often occurs to generate truly active species for catalytic reactions, but the stability and mass activity of the catalysts is a huge challenge. A method that combines cation doping with morphology control strategies and constructs an amorphous-crystalline heterostructure is proposed to achieve deep reconstruction of the catalyst during the electrochemical activation process, thereby significantly improving catalytic activity and stability. Amorphous iron borate (FeBO) is deposited on cobalt-doped nickel sulfide (Co-Ni3S2) crystals to form ultrathin nanosheet heterostructures (FeBO/Co-Ni3S2) as bifunctional electrocatalysts for the OER and methanol oxidation reaction (MOR). During the OER process, FeBO/Co-Ni3S2 is deeply reconstructed to form a NiFeOOH/Co-Ni3S2 composite structure with ultrathin nanosheets with abundant amorphous-crystalline interfaces to ensure structural stability. Furthermore, Co-Ni3S2 electrocatalysts were synthesized via nickel foam (NF) self-derivation, which resulted in strong adhesion between the catalyst and substrate and formed a hierarchical structure consisting of interconnected nanosheets with excellent mass transfer and abundant active sites to increase the activity and stability of the electrocatalyst. The dual-electrode electrolyzer requires cell voltages of 1.58 and 1.44 V to achieve water and methanol overall electrolysis at a current density of 10 mA cm-2 and keep working over 100 and 25 h, respectively. This strategy provides a new way to promote reconstruction to construct excellent bifunctional electrocatalysts.

Microwave-Assisted synthesis of interconnected holey nanosheets of zinc vanadate for High-Performance supercapacitor

Developing electrode materials with high energy density and cyclic stability is crucial for advanced supercapacitor (SC) devices in the field of green energy technologies. However, the choice of electrode material and its synthesis approaches significantly impact the electrochemical performance of these devices. In this study, the effect of microwave power on the synthesis process, physicochemical properties and electrochemical performance of zinc vanadate (ZVO) is investigated. The interconnected “holey” ZVO nanosheets are synthesized using a microwave-assisted chemical synthesis process with different microwave powers with shorter reaction time (3 min). X-ray diffraction confirmed that the synthesized ZVO has an orthorhombic crystal structure. At lower microwave power (450 W), interconnected holey nanosheets are observed. When the power is increased above 450 W, the nanosheets disintegrated into an interconnected network of nanopebbles. The ZVO nanosheet electrode showed a specific capacity of 145.16 mAh/g and a specific capacitance of 871.01 F/g at 5 A/g, with a capacity retention of 96% after 5000 cycles. Furthermore, an aqueous asymmetric hybrid supercapacitor (AHSC) device with ZVO-1//AC configuration achieved a specific energy density of 32.77 W/kg at a power density of 400 W/kg with a capacity retention of 82.8% after 2000 cycles. These findings strongly indicate that the developed ZVO holey nanosheets can be used as a potential electrode material for high-performance SC devices.

In Situ Construction of Hierarchical Nickel-Cobalt Hydroxides Derived from Metal-Organic Frameworks for High-Performance Nickel-Zinc Batteries.

Rechargeable nickel-zinc (Ni-Zn) batteries hold great promise for large-scale applications due to their relatively high voltage, cost-efficient zinc anode, and good safety. However, the commonly used cathode materials are susceptible to overcharging and experience irreversible capacity degradation, primarily as a result of low electrical conductivity and substantial limitations in volume-constrained proton diffusion. Here, we present a robust methodology for synthesizing hierarchical nickel-cobalt (Ni-Co) hydroxides characterized by hollow interiors and interconnected nanosheet shells with the help of in situ formed metal-organic frameworks (MOFs). The templating effect of the MOF induced the hierarchical structure, while the chemical etching of MOFs by Ni2+ ions resulted in a hollow structure, thereby enhancing the surface area. Theoretical calculations suggested that incorporation of cobalt reduces the band gap, thereby improving electronic conductivity, and lowered the deprotonation energy, which mitigated overcharge issues. These advantages conferred improved specific capacity, rate capability, and cyclic stability to the Ni-Co hydroxide. The Ni-Zn cell delivered specific energy values of 338 Wh kg-1 at 1.62 kW kg-1 and 142 Wh kg-1 at 29.89 kW kg-1. Our investigations undercoreed the critical role of MOFs as intermediates in the preparation of multi-component hydroxide and the construction of hiearchical structures to achieve superior performance.

Perfect Is Perfect: Nickel Prussian Blue Analogue as A High-Efficiency Electrocatalyst for Hydrogen Peroxide Production.

Prussian blue analogues (PBA) are a large family of functional materials with diverse applications such as in electrochemical fields. However, their use in the emerging two-electron oxygen reduction reaction for clean production of hydrogen peroxide (H2O2) is lagging. Herein, a general solvent exchange induced reconstruction strategy is demonstrated, through which an abnormal NiNi-PBA superstructure is synthesized as a high-performance electrocatalyst for H2O2 generation. The resultant NiNi-PBA superstructure has a stoichiometric composition with saturated lattice water, and a leaf-like morphology composed of interconnected small-size nanosheets with identical orientation and predominate {210} side surface exposure. Our studies show that the Ni-N centers on {210} facets are the active sites, and the saturated lattice H2O favors a six-coordinated environment that results in high selectivity. The "perfect" structure including stoichiometric composition and ideal facet exposure leads to a high selectivity of ~100 % and H2O2 yield of 5.7 mol g-1 h-1, superior to the reported MOF-based electrocatalysts and most other electrocatalysts.

Self-Adaptive Electrochemistry of Phosphate Cathodes toward Improved Calcium Storage.

Polyanion phosphates exhibit great potential as calcium-ion battery (CIB) cathodes, boasting high working voltage and rapid ion diffusion. Nevertheless, they frequently suffer from capacity decay with irreversible phase transitions; the underlying mechanisms remain elusive. Herein, we report an adaptively layerized structure evolution from discrete NaV2O2(PO4)2F nanoparticles (NPs) to interconnected VOPO4 nanosheets (NSs), triggered by electrochemical (de)calcification, leading to an improvement in Ca2+ storage performance. This electrochemistry-driven self-adapted layerization occurs over approximately 200 cycles, during which NPs undergo a "deform/merge-layerization" process, transitioning from a three-dimensional to a two-dimensional atomic structure, with a distinct 0.68 nm lattice spacing. The transition mechanism is demonstrated to be linked to the gradual separation of structural Na+ and F-. The resultant VOPO4 NSs exhibit exceptional Ca2+ diffusion kinetics (3.19 × 10-9 cm2 s-1, currently the optimal value among inorganic cathode materials for CIBs), enhanced capacity (∼100 mA h g-1), longevity (over 1000 cycles at 50 mA g-1), and high rate (84% retention rates when increasing current density from 50 to 200 mA g-1). Employing advanced electron microscopy, this study reveals an electrochemical activation-induced structure evolution at the atomic level, providing valuable insights into the design of high-performance CIB cathodes.

Multi-interface and rich-defects 1T phase MoS2 combine with FeS anchored on reduced graphene oxide for efficient alkaline hydrogen evolution

Exploring and fabricating noble-metal-free and cost-effective electrocatalysts to minimise the excessive potential required is of great significance for alkaline hydrogen evolution reaction (HER). Herein, we report FeS/1T-MP MoS2@rGO heterostructure with 1T and 2H mixed phase MoS2 (1T-MP MoS2) combining with FeS anchored on reduced graphene oxide (rGO) matrix, which is synthetized by utilizing Anderson polyoxometalate as Fe–Mo precursor by a facile hydrothermal method. The FeS/1T-MP MoS2@rGO heterostructure in the form of interconnected nanosheet arrays with multiple interfaces and rich-defects, which is in favor of the immersion of the electrolyte and exposing more active sites. Benefiting from the synergistic advantages of 1T-MoS2, FeS and rGO, FeS/1T-MP MoS2@rGO heterostructure delivers enhanced conductivity, enlarged electrochemical active surface area, and eventually promote the HER kinetics. As expected, FeS/1T-MP MoS2@rGO heterostructure emerges prominent HER activity with low overpotentials of 102 and 256 mV to achieve current density of 10 and 100 mA cm−2, outperforming vast majority of the advanced 1T MoS2-based alkaline HER electrocatalysts.

In-situ surface reconstruction of Co-based imidazole zeolite framework by Mo etching for superior water oxidation

Although zeolitic imidazolate frameworks (ZIFs) possess the merits of orderly porosity, high permeability, and easy functionalization, the transformation of ZIFs into the real active species and the promotion of the catalytic efficiency and stability are still challenging. Herein, CoMo-based three-dimensional (3D) hollow nanocages composed of interconnected nanosheets are fabricated by in-situ etching metal–organic framework (ZIF-67) under the aid of MoO42−. X-ray photoelectron spectroscopy (XPS) and in-situ Raman confirm that Mo leaching can accelerate surface reconstruction and generate CoOOH active sites after continuous oxidation. Benefiting from the nanostructure and electronic properties after surface reconstruction, the engineered CoMo-30 exhibits the lowest overpotential of 280 mV at 30 mA cm−2 and robust stability over 110 h in 1 M KOH media for oxygen evolution reaction (OER), which significantly surpasses the other counterparts and commercial RuO2. Density functional theory (DFT) calculations indicate that CoMo-30 has a lower free energy of *O → *OOH as rate determining step (RDS), suggesting that CoOOH sites play a crucial role in enhancing the activity and kinetics of OER. This work provides valuable insights into the rational design of hollow structures and the structure-composition-activity relationship during the electrochemical reaction process.

Self-supported SnS/MoO3 electrocatalyst for supercapacitor and hydrogen evolution reaction

Improving the efficiency of energy storage and conversion requires designing electrodes with a hybrid heterostructure. Overall, a single component of MoO3 suffers from poor cycling stability and sluggish intrinsic conductivity. SnS@MoO3/MoS2 nano-heterostructure is effectively grown on 3D nickel foam using facile hydrothermal techniques to address this issue. The structure, composition, and morphology of as-prepared nano-heterostructures are characterized using X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscope, respectively. The MS-10 nano-heterostructure shows interconnected nanosheets with a self-supported porous structure. As grown, the MS-10 nano-heterostructure electrode exhibits excellent specific capacitance of 5051 Fg−1 at 2 Ag−1 with good stability. Moreover, the MS-10 electrode achieves good results in alkaline water splitting. The MS-10 nano-heterostructure presents low over potential with good stability of 12 h. This work is anticipated to advance efforts to create SnS@MoO3/MoS2 nano-heterostructure with interconnected nanosheets and self-supported porous structure, which are considered potential candidates for energy storage and conversion.

Constructing a Self-Supported Bifunctional Multiphase Heterostructure for Electrocatalytic Overall Water Splitting.

Developing well-performing and stable bifunctional electrocatalysts is of great importance for efficient green hydrogen production through water electrolysis. Herein, a three-dimensional self-supported CoMoS3.13/FeS2/Co3S4 on carbon paper (FeCoMoS/CP) heterostructure with interconnected nanosheets for overall water splitting was fabricated by a facile hydrothermal method followed by vulcanization treatment. The FeCoMoS/CP heterostructure with high structural integrity and more accessible active sites can effectively optimize the electronic structure through component regulation to achieve enhanced catalytic activity. Significantly, the FeCoMoS/CP required overpotentials of 257 mV at 50 mA cm-2 for OER and 280 mV at 20 mA cm-2 for HER. Importantly, the assembled FeCoMoS/CP||FeCoMoS/CP alkaline electrolyzer achieved a superior cell voltage of 1.48 V at 10 mA cm-2 with superb long-term stability, which implies a remarkable electrocatalytic performance of the FeCoMoS/CP heterostructure for overall water splitting. This work provides an applicable route for synthesizing high-performance bifunctional catalysts toward water electrolysis.

Crystalline NiCo2O4 and amorphous NiCo2S4 heterostructured electrode for high-performance asymmetric supercapacitors

The construction of well-designed heterostructures and phase engineering have been verified to be a promising strategy to improve electrochemical performance of supercapacitors. However, it is still a challenge to construct well-defined amorphous/crystalline hetero-phase electrode with plentiful heterointerfaces. Herein, a high-performance self-supported NiCo2O4@NiCo2S4 electrode with crystalline NiCo2O4 and amorphous NiCo2S4 heterostructure is synthesized by electrodeposition-anneal-electrodeposition procedure. The interconnected nanosheet structure and rich heterointerfaces effectively promote the exposure of surface area and accelerate the electron/ion transfer kinetics of redox reaction as well as restrain the volume expansion and structural collapse, thus greatly enhancing the electrochemical performance and stability. Impressively, the advanced NiCo2O4@NiCo2S4 electrode delivers a prominent specific capacitance of 2243.0 F g−1 at 1 A g−1 along with outstanding cyclic stability with a capacity retention of 83.29 % at 10 A g−1 after 5000 cycles. Moreover, the asymmetric supercapacitor (ASC) assembled by NiCo2O4@NiCo2S4 cathode and active carbon anode displays a maximum energy density of 66.7 Wh kg−1 at 625.3 W kg−1 and favorable cycling stability (77.23 % after 10,000 cycles at 10 A g−1).

Deciphering Sodium-Ion Storage: 2D-Sulfide versus Oxide Through Experimental and Computational Analyses.

Transition metal derivatives exhibit high theoretical capacity, making them promising anode materials for sodium-ion batteries. Sulfides, known for their superior electrical conductivity compared to oxides, enhance charge transfer, leading to improved electrochemical performance. Here, a hierarchical WS2 micro-flower is synthesized by thermal sulfurization of WO3. Comprising interconnected thin nanosheets, this structure offers increased surface area, facilitating extensive internal surfaces for electrochemical redox reactions. The WS2 micro-flower demonstrates a specific capacity of ≈334mAhg-1 at 15mAg-1, nearly three times higher than its oxide counterpart. Further, it shows very stable performance as a high-temperature (65°C) anode with ≈180mAhg-1 reversible capacity at 100mAg-1 current rate. Post-cycling analysis confirms unchanged morphology, highlighting the structural stability and robustness of WS2. DFT calculations show that the electronic bandgap in both WS2 and WO3 increases when going from the bulk to monolayers. Na adsorption calculations show that Na atoms bind strongly in WO3 with a higher energy diffusion barrier when compared to WS2, corroborating the experimental findings. This study presents a significant insight into electrode material selection for sodium-ion storage applications.

(FeO)2FeBO3 nanoparticles attached on interconnected nitrogen-doped carbon nanosheets serving as sulfur hosts for lithium–sulfur batteries

(FeO)2FeBO3 nanoparticles attached on interconnected nitrogen-doped carbon nanosheets serving as sulfur hosts for lithium–sulfur batteries

Cobalt phosphide embedded on interconnected ultrathin carbon nanosheets as an electrocatalyst for hydrogen evolution in alkaline medium

A highly effective hydrogen evolution reaction (HER) electrocatalyst was developed by combining Co2P nanoparticles (Co2P NPs) embedded on interconnected and ultrathin carbon nanosheets (CNS) through a facial in-situ thermal decomposition of the cobalt-triphenylphosphine complex. CNS were derived from the pyrolysis of sodium citrate in one step, resulting in an interconnected ultrathin nanosheet structure with a small thickness. The interaction between Co2P NPs and CNS boosted the electron transfer rate, resulting in a remarkable electrocatalytic performance toward the HER in an alkaline solution with excellent durability. An overpotential of −200 mV vs. RHE was sufficient to afford a current density of −10 mA cm−2 with a Tafel slope of 83.4 mV dec−1 in potassium hydroxide medium (1.0 M), which are lower than that of Co2P nanoparticles (-250 mV) with Tafel slope 93.3 mV dec−1. The electrochemical impedance spectroscopy data illustrated that the mutual coupling between the Co2P NPs and CNS supports the electrochemical HER performance and accelerates the kinetic of electron transfer. The high HER activity of the novel Co2P NPs/CNS catalyst is ascribed to the presence of CNS robust support.

Flexible yet impermeable composites with wrinkle structured BNNSs assembling for high-performance thermal management

Efficient thermal management has become one of the most critical issues of electronics because of the high heat flux generated from highly integrated, miniaturized, and increased power. Here we report highly flexible composites with aligned and overlapping interconnected boron nitride nanosheets (BNNSs) assembled in wrinkle structures. Besides high in-plane thermal conductivity of more than 26.58 W m−1 K−1, such structure rendered enhanced through-plane conduction along with increasing pre-stain. As thermal interface materials (TIMs) of both rigid and flexible devices, the composites revealed an outstanding thermal cooling capability outperforming some commercial TIMs. During a record-long bending process of more than 3000 cycles, the maximum temperature fluctuation of the flexible device with 100%-prestrained composite was only within 0.9 °C, less than one-third of that with commercial thermal pad. Moreover, the composite revealed a superior impermeability for flexible seals. Our results illustrate that the composites could be an ideal candidate for the thermal management of emerging flexible electronics.

Catalytic membranes assembled by Co–Fe Prussian blue analogues functionalized graphene oxide nanosheets for rapid removal of contaminants

The catalytic membrane, combining confinement effect with advanced oxidation processes, exhibits great potential as an efficient technology for removing contaminants and mitigating membrane fouling. Herein, the Prussian blue analogues (PBAs) functionalized graphene oxide (GO) membranes, referred as PGMs, was successfully fabricated. It exhibited a package-like confined structure where Co–Fe PBAs were encapsulated within interconnected GO nanosheets. The surface properties, internal structure as well as the catalytic performance of PGMs were controlled by adjusting the amount of Co–Fe PBAs anchored on GO nanosheets. The designed PGM as efficient peroxymonosulfate activator exhibited exceptional catalytic performance, achieving complete removal of bisphenol A (BPA) with a retention time of 31 ms. The corresponding first-order rate constant was 6000 min−1, which surpassed conventional batch system by four orders of magnitude (0.2194 min−1). Moreover, the redox cycle involving Fe2+ and Co3+, coupled with the effective suppression of ion leaching from Co–Fe PBAs nanoparticles (<10 μg/L) through GO protective layers, ensured the stable catalytic performance of PGM over 144 h. This study employs a novel approach to confine catalytic nanoparticles within two-dimensional nanosheets, demonstrating the potential applications of the resulting confined membrane in water treatment.

Ligand-Induced Electronic Structure Modulation of Self-Evolved Ni3S2 Nanosheets for the Electrocatalytic Oxygen Evolution Reaction.

Modulating the electronic structure of the electrocatalyst plays a vital role in boosting the electrocatalytic performance of the oxygen evolution reaction (OER). In this work, we introduced a one-step solvothermal method to fabricate 1,1-ferrocene dicarboxylic acid (FcDA)-decorated self-evolved nickel sulfide (Ni3S2) nanosheet arrays on a nickel foam (NF) framework (denoted as FcDA-Ni3S2/NF). Benefiting from the interconnected ultrathin nanosheet architecture, ligand dopants induced and facilitated in situ structural reconstruction, and the FcDA-decorated Ni3S2 (FcDA-Ni3S2/NF) outperformed its singly doped and undoped counterparts in terms of OER activity. The optimized FcDA-Ni3S2/NF self-supported electrode presents a remarkably low overpotential of 268 mV to achieve a current density of 10 mA cm-2 for the OER and demonstrates robust electrochemical stability for 48 h in a 1.0 M KOH electrolyte. More importantly, in situ electrochemical Raman spectroscopy reveals the generation of catalytically active oxyhydroxide species (NiOOH) derived from the surface construction during the OER of pristine FcDA-Ni3S2/NF, contributing significantly to its superior electrocatalytic performance. This study concerns the modulation of electronic structure through ligand engineering and may provide profound insight into the design of cost-efficient OER electrocatalysts.

Efficient cleanup of highly viscous spilled oil using a fast solar-heating and super hydrophobic sponge

A solar-heating sponge, in which the polypyrrole (PPy) coating plays the role of photothermal converter and carbon nanotubes (CNTs) act as the thermal conductor, was fabricated. The sponge can effectively convert sunlight into heat and fast conduct heat so that the temperature can rise to 80 °C within 30 s under 1 sun irradiation. Besides, the temperatures of the other parts rise synchronously with the top surface, unlike most reported sponges which had temperature differences between different parts. This advantage can avoid the decrease of diffusion rate of the oil in application. The sponge also exhibits super hydrophobility with a high water contact angle of 151.2°. The excellent solar-heating ability and hydrophobility make the sponge an efficient viscous oil adsorbent. The sponge can continuously and rapidly remove the spilled oil under solar irradiation. The coating composed of interconnected PPy nanosheets is firmly fixed on the surface of the elastic matrix via multiple H bonds. After 10 adsorption-desorption cycles, the adsorption capacity still maintains 97.2 %, without any change in hydrophobility. These advantages including fast solar-heating, super hydrophobility and high regenerability demonstrate that the sponge has great potential in oil spill treatment, especially highly viscous oils.

One-pot synthesis of interconnected carbon-coated silicon nanosheets from clay minerals for high-performance lithium-ion battery anodes

The silicon nanosheet/carbon composite emerges as a promising anode material for the next-generation commercial lithium-ion batteries. However, complex, costly, and energy-intensive synthesis procedures impede its practical application. Herein, the carbon-coated silicon nanosheets (Si/C) have been successfully synthesized via a one-pot strategy, involving a modified magnesiothermic reduction of talc followed by a reaction with CO2. The distinct chemical composition and layered nanostructure of talc enable the retention of Si nanosheets during exothermic reactions without additional templates or heat absorbents. The method shows significant potential for the scalable production of Si/C owing to the abundant silicon source, sustainable carbon source, and straightforward protocol. The resulting Si/C displays a hierarchical porous structure, with both macropores and mesopores, and an interconnected network of carbon-coated Si nanosheets. These structural characteristics facilitate rapid Li+ diffusion and enable the material to accommodate the lithiation-induced mechanical strains. As a result, the Si/C electrode exhibits outstanding electrochemical performance, including a remarkable rate capability (with a specific capacity of 1220 mAh g−1 at 10.0 A g−1) and a high initial Coulombic efficiency of 88%. The work opens a new avenue for the development of Si/C composites from natural clay minerals through an economical and scalable strategy, which would contribute to the practical application of advanced Si-based anodes in lithium-ion batteries.

Adjusting surface electron density of heterostructured NiCo LDH/MXene/NF material to improve its electrocatalytic performance in hydrogen evolution reaction

Hydrogen production by water electrolysis has attracted much interest in the field of renewable energy storage due to its high efficiency and low environmental impact. Catalytic activity of transition metal-based electrode materials can be effectively improved by adjusting their composition and/or structure. In this study, MXene nanosheets are electrophoretically deposited on foamed nickel (MXene/NF), and further coated by NiCo layered double hydroxides (LDH) nanosheets, also by electrophoresis, to obtain the heterostructured and highly conductive NiCo LDH/MXene/NF electrode, highly active in the hydrogen evolution reaction. Uniform surface distribution of three-dimensional interconnected nanosheets is demonstrated by SEM and TEM. The electrode surface is fully wet within 150 ms, indicating excellent hydrophilicity. The highly conductive NiCo LDH/MXene/NF electrode material exhibits a potential overshoot of 123 mV vs. RHE at a current density of 10 mA cm−2, with a Tafel slope of +86.6 mV dec−1. Long-term cyclic testing confirms good stability of the newly prepared electrode material in the hydrogen evolution reaction.