Nanosheet Electrode Research Articles

FeSe2/CoSe nanosheets for efficient overall water splitting under low cell voltages

Electrocatalysts with high activity and stability for hydrogen generation from water have become the increasing demand of future energy system. Despite all the advances in the synthesis of transition metal selenide nanostructures, the fabrication of two-dimensional (2D) electrocatalyst remains a major challenge. Here, a unique 2D FeSe2/CoSe nanosheet structure is synthesized by hydrothermal and selenization processes. In an alkaline solution, a FeSe2/CoSe nanosheet electrode exhibits a low overpotential of 73 mV for 10 mA cm−2 in the hydrogen evolution reaction. Furthermore, as an anode in oxygen evolution reaction, its surface can self-transform to a stable FeOOH/CoOOH layer without any morphology transition, and it requires only 183 mV to reach 10 mA cm−2. In a two-electrode system, it needs a cell voltage of only 1.48 V to achieve 10 mA cm−2. This work provides an easy way to construct bimetallic transition metal selenide electrocatalysts for efficient overall water splitting.

Electroconversion synthesis of Ni/Co layered nanomaterials for high-performance supercapacitors

Ni/Co(OH) 2 nanosheets were prepared through an electroconversion reaction with CoCl 2 .6 H 2 O and NiCl 2 .6 H 2 O as raw materials and without an added structural guiding agent. NiCo 2 O 4 was obtained by calcination with Ni/Co(OH) 2 as a precursor. The structure and morphology of Ni/Co(OH) 2 and NiCo 2 O 4 were characterized by XRD, FTIR, XPS, and SEM. The characterization results show that the particle size range of Ni/Co(OH) 2 with a three-dimensional nanostructure is 10–84 nm, and it is formed by staggered stacking of nanosheets with a thickness of approximately 19 nm. The electrochemical test results show that the specific capacitance of the Ni/Co(OH) 2 nanosheet electrode in 1 M KOH electrolyte and 1 A/g current density is as high as 908.33 F/g, which can be attributed to its unique three-dimensional nanolayered structure, and as a result, more redox reaction active sites can be provided in the charge storage process. In addition, the structure of the Ni/Co(OH) 2 nanosheet electrode can slow down the volume change during the charge–discharge cycle and maintain the stability of the structure. Under the high current density of 10 A/g, the specific capacitance retention rate is 71% at 1500 cycles and 74% at 3500 cycles, but then it shows a downwards trend. The capacitance retention rate fluctuates between 60% and 30%. After 10000 cycles, the specific capacitance retention rate is still 30%, indicating that the electrode exhibits a good cycle performance. Ni/Co(OH) 2 and NiCo 2 O 4 nanosheets are successfully prepared by electroconversion-heat treatment method without adding a structural directing agent, which can be used as electrode materials for supercapacitors. The specific capacitance of the binder-free Ni/Co(OH) 2 nanosheet electrodes at a current density of 1 A/g in 1 M KOH electrolyte is 990.91 F/g. When the current density increases to 10 A/g, the specific capacitance of Ni/Co(OH) 2 nanosheet electrode can still reach 604.17 F/g. The specific capacitance retention rate is 71% at 1500 cycles and even increased to 74% at 3500 cycles. This work provides a facile and efficient synthesis strategy for surfactant-free preparation of three-dimensional nano hierarchical Ni/Co(OH) 2 electrode materials for high-performance supercapacitors. • Ni/Co(OH) 2 and NiCo 2 O 4 are prepared by electroconversion-heat treatment method without any structural directing agents. • Ni/Co(OH) 2 shows better electrochemical performance, with a specific capacitance of 990.91 F/g at 1 A/g. • The three-dimensional structure of Ni/Co(OH) 2 has a large specific surface area and small diffusion resistance, which can accelerate ion diffusion and electron transport, and slow down volume expansion.

Synthesis of porous cobalt oxide nanosheets: highly sensitive sensors for the detection of hydrazine

A highly sensitive, reliable, and reproducible sensor for detecting hydrazine was fabricated using a porous cobalt oxide (Co2O3) nanosheets electrode. The Caffeine assisted Co2O3 nanosheets were prepared by a low-temperature aqueous chemical growth method. The morphology, phase purity, and porosity of Co2O3 nanosheets were examined via SEM, XRD, and BET techniques. SEM results reveal the hexagonal sheet-like morphology of synthesized Co2O3 nanosheets, while the XRD technique illustrates high phase purity. Furthermore, the BET technique demonstrated the increased surface area exhibited by the newly synthesized Co2O3 nanomaterial. The hydrazine sensor based on the Co3O4 nanosheet electrode demonstrated relatively high sensitivity (1.632 μA cm−2 μM−1) and a rather low detection limit (0.05 μM) due to the fast electro-oxidation of hydrazine catalyzed by Co3O4 nanosheets. The unique porous structure of Co3O4 nanosheets offers a promising probe candidate for efficient electrochemical sensors of hydrazine.

Electrochemical immunosensor with PVP/WS2 nanosheets electrode for fibroblast growth factor 21 detection based on metal organic framework nanozyme

A novel electrochemical immunosensor with poly(vinyl pyrrolidone)-tungsten disulfide (PVP/WS2) nanosheets electrode was fabricated for fibroblast growth factor 21 (FGF-21) detection based on gold nanoparticles and metal organic framework (AuNPs/MOFs) nanozyme. The PVP/WS2 nanosheets enabled direct antibody immobilization on the electrode surface and exhibited high conductivity. The MOFs nanozyme peroxidase-like activity efficiently converted a o-phenylenediamine substrate to 2,2-diaminoazobenzene, which generated an ideal electrochemical signal for monitoring FGF-21 concentrations. The electrochemical immunosensor was fully characterized via Impedance spectroscopy (EIS), Cyclic voltammetry (CV), Squarewave voltammetry (SWV), Scanning electron microscope (SEM), Transmission electron microscope (TEM) and Ultraviolet-visible spectroscopy (UV–vis). The biosensor exhibited a good linear relationship over the range 1 pg mL−1 to 100 ng mL−1, and a superior limit of detection (LOD) as low as 0.24 pg mL−1. It was successfully used to determine FGF-21 concentrations in serum samples and achieved satisfactory results, indicating great potential applications in clinical diagnostics.

Facile preparation of functionalized and oxygen-deficient V2O5 nanosheets electrode as a versatile platform for biomimetic- and photoelectro-catalysis

Facile preparation of functionalized and oxygen-deficient V 2 O 5 nanosheets modified electrode with enhanced biomimetic- and photoelectro-catalytic activity • One-step preparation of functionalized V 2 O 5 nanosheets electrode was demonstrated. • Roles of formamide in functionalizing V 2 O 5 nanosheets electrode was uncovered. • The obtained electrode (FTO|exf-V 2 O 5 ) can reduce Ag ions to Ag nanoparticles. • FTO|exf-V 2 O 5 shows remarkably high H 2 O 2 affinity and biomimetic activity. • Photoelectrocatalytic activity of FTO|exf-V 2 O 5 to methanol oxidation was explored. In this study, we present a facile and scalable preparation of formamide-functionalized and oxygen-deficient V 2 O 5 nanosheets (thickness: 30 ∼ 40 nm) modified electrode (FTO| exf -V 2 O 5 ) with promising peroxidase-like and photoelectrocatalytic activity. FTO| exf -V 2 O 5 was prepared by the direct top-down exfoliation of the V 2 O 5 sub-micron plates (thickness: 300 ∼ 550 nm) modified electrode (FTO| micro -V 2 O 5 ) in the presence of formamide as the exfoliation agent at mild conditions. Formamide molecules were found to adsorb on FTO| exf -V 2 O 5 and serve as the active sites for the reduction of noble metal, which not only enables the application of FTO| exf -V 2 O 5 for the recovery of noble metals but also allows further functionalization and electrocatalytic oxidation of H 2 O 2 . As compared with FTO| micro -V 2 O 5 , FTO| exf -V 2 O 5 had significantly higher oxygen vacancy (V O ) content and exhibited remarkably enhanced peroxidase activity with an ultra-low Michaelis-Menten constant of 68.24 μM and a high catalytic constant (or maximal turnover frequency) of 0.28 s −1 . Finally, FTO| exf -V 2 O 5 with lower dimension and higher V O content showed improved kinetics of charge-transport and interfacial charge-transfer, resulting in the enhanced activity towards photoelectrocatalytic oxidation of water and methanol. This work opens a new avenue for the preparation of exfoliated 2-D material based platform for biomimetic catalysis and energy conversion.

Facile Fabrication of Bifunctional Hydrogen Catalytic Electrodes for Long-Life Nickel-Hydrogen Gas Batteries.

The renaissance of long-lasting nickel-hydrogen gas (Ni-H2) battery by developing efficient, robust, and affordable hydrogen anode to replace Pt is particularly attractive for large-scale energy storage applications. Here, we demonstrate an extremely facile corrosion induced fabrication approach to achieve a self-supporting hydrogen evolution/oxidation reaction (HER/HOR) bifunctional nanosheet array electrode for Ni-H2 battery. The electrode is constituted by ultrafine Ru nanoparticles on Ni(OH)2 nanosheets grown on nickel foam. Experimental and theoretical calculation results reveal that the electrode with optimized geometric and electronic structures ensures the efficient and robust catalytic hydrogen activities. The fabricated Ni-H2 battery using the Ru-Ni(OH)2/NF anode with an industrial scale areal capacity of 16 mAh cm-2 demonstrates a high energy density, good rate capability and excellent durability without capacity decay over 1800 h. This study casts light on the development of low manufacturing cost and high performance bifunctional hydrogen catalytic electrodes for future hydrogen energy applications.

Construction of Pd/Ni2P-Ni foam nanosheet array electrode by in-situ phosphatization-electrodeposition strategy for synergistic electrocatalytic hydrodechlorination

Designing a high-efficiency electrocatalyst with low Pd loading on the electrodes is the key to the electrocatalytic hydrodechlorination (EHDC) of chlorophenols (CPs) but still challenging. Herein, a novel three-dimensional network structure Pd/Ni2P-Ni foam nanosheet array electrode with Pd loading content only 1 wt% was prepared by an in-situ phosphatization-electrodeposition strategy for robust EHDC. The EHDC performance of the constructed Pd/Ni2P-Ni foam electrode was tested with 4-CP as the model pollutant. Complete dechlorination is achieved within 90 min, and the consumption of Pd is reduced by 50 %. The mechanism study shows that the improvement of EHDC performance can be attributed to the synergistic effect of Ni2P nanosheets and Pd NPs, in which Ni2P replaces Pd0 to produce atomic hydrogen (Hads), and promotes more Pd2+ generation, which is beneficial to the fracture of the C-Cl bond, thus improving the mass activity of Pd and the EHDC performance simultaneously. This work provides a simple and practical strategy for designing low noble metal supported catalysts with high EHDC performance.

MOFs assisted construction of Ni@NiOx/C nanosheets with tunable porous structure for high performance supercapacitors

High specific surface area (SSA) and optimized porous structures are necessary for supercapacitors electrodes. MOFs have porous structure which make them potential candidates for electrodes materials. Here, a MOF derivative with Ni@NiOx nanoparticles embedded in porous carbon nanosheets (Ni@NiOx/C) is prepared by hydrothermal method and carbonization process. Among them, the porous structure is tuned by the ZnO templates. Results show that the amount of doped ZnO nanoparticles can affect the morphology, porous structure and electrochemical properties of Ni@NiOx/C nanosheets electrodes. In three electrode system, the Ni@NiOx/C-2 electrode has a high specific capacitance of 752 F g−1 (at 1 A g−1) and prominent rate performance (the initial capacitance retains 56% when the current density increased to 100 A g−1). After 10,000 cycles, 99% of the initial capacitance is maintained. The assembled asymmetric device (Ni@NiOx/C-2//AC) also exhibits a high-power density (15,840 W kg−1).

Construction of three-dimensional (3D) vertical nanosheets electrode with electrochemical capacity applied to microsupercapattery

The preparation of heterostructure composites is regarded as an effective measure to enhance the electrochemical performances of pure component materials for energy conversion and storage. This paper reports a rapid microwave process to synthesize novel hierarchical multi-walled carbon nano-tubes and graphene nano-ribbons/Co–Ni LDH (MWGR/Co–Ni LDH) composites with superior performances in supercapattery. MWCNTs-GONRs with high conductivity, structural stability and electrochemical properties, and LDH with the construction of p-n junction are also profitable to transpire redox reaction. Thus, MWGR/Co–Ni LDH exhibites the distinctive heterostructure and splendid electrochemical properties (a high specific capacitance of 1030.2 C g−1 at 1 A g−1). In addition, the as-prepared MWGR/Co–Ni LDH//AC device performs the maximum energy density of 47.2 Wh kg−1 at power density of 0.85 kW kg−1 and good cycling performance of 88.8% retention after 10,000 cycles at 10 A g−1. Furthermore, the assembled asymmetric supercapattery (ACS) is adequate to provide energy for multiple lights emitting diodes (LEDs), which holds great promising practical applications for supercapattery.

Toward Enhanced Electrochemical Performance by Investigation of the Electrochemical Reconstruction Mechanism in Co2V2O7 Hexagonal Nanosheets for Hybrid Supercapacitors.

As for hybrid supercapacitors, it is important to enhance the long cycling performance and high specific capacitance. In this paper, cobalt vanadate (Co2V2O7) hexagonal nanosheets on nickel foam are manufactured by a facile hydrothermal method and then transformed into numerous smaller size interconnected hierarchical nanosheets without any shape change via electrochemical reconstruction. Benefiting from the favorable architecture of hierarchical nanosheets via electrochemical reconstruction, the Co2V2O7 hexagonal nanosheet electrode exhibits a remarkable long cycling performance with 272% specific capacitance retention after 100,000 cycles at a current density of 5 A g-1 and then displays an increasing specific capacitance of 1834 F g-1 (tested at 1 A g-1). Furthermore, an aqueous hybrid supercapacitor device based on the Co2V2O7 hexagonal nanosheet electrode exhibits a high energy density of 35.2 Wh kg-1 at a power density of 1.01 kW kg-1 and an excellent cyclic stability with 71.4% capacitance retention after 10,000 cycles at 5 A g-1. These results offer a practicable pathway for enhancing the electrochemical properties of other metal oxides through electrochemical reconstruction.

Scalable preparation of a CuO nanosheet arrayviacorrosion engineering for selective C–C coupling in CO2electroreduction

A CuO nanosheet array electrode was preparedviaa facile corrosion strategy for the electrochemical CO2reduction reaction. In order to produce C2+products efficiently, both abundant defect sites and moderate surface roughness are required.

Preparation of mixed-valent manganese-vanadium oxide and Au nanoparticle modified graphene oxide nanosheets electrodes for the simultaneous determination of hydrazine and nitrite

• Mixed valent metal–metal oxides were performed by SEM-EDX, XPS, CV, EIS techniques. • Simultaneous and individual determination of hydrazine and nitrite. • LOD for LSV 3.0 and 10.0 µM for hydrazine and nitrite, respectively. • AuNP/MnOx-VOx/ERGO was tested in river water and food samples. In this study, for the first time in the literature, simultaneous and individual determination of hydrazine and nitrite have performed by combining the triple electrocatalytic properties of electrochemically reduced graphene oxide (ERGO), multivalent metal oxide (MnOx-VOx) films and gold nanoparticles (AuNPs). Characterization studies of AuNP/MnOx-VOx/ERGO electrode were performed using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM) methods. The determinations of hydrazine and nitrite in pH 8 BR buffer solution were studied using linear sweep voltammetry (LSV) and amperometry methods. The limit of detection (LOD) for simultaneous detection was 3.0 and 10.0 µM for hydrazine and nitrite, respectively, and the LOD for amperometric detection was 0.1 and 0.33 µM, respectively. AuNP/MnOx-VOx/ERGO electrode was tested for the determination of hydrazine and nitrite in river water and food samples, and this electrode provides a recovery of 91.0% to 113.0%. Also, the electrode has practical preparation, good repeatability, selectivity, accuracy.

Food seasoning-derived gel polymer electrolyte and pulse-plasma exfoliated graphene nanosheet electrodes for symmetrical solid-state supercapacitors.

Kitchen sea salt or table salt is used every day by cooks as a food seasoning. Here, it is introduced into a gel polymer (poly(vinyl) alcohol (PVA)-table salt) for use as an electrolyte, and an electrode was constructed from graphene nanosheets for use as symmetrical solid-state supercapacitors. The graphene sheets are prepared by a pulse control plasma method and used as an electrode material, and were studied by X-ray diffraction (XRD), Raman spectroscopy, as well as scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). A specific capacitance of 117.6 F g−1 at 5 mV s−1 was obtained in a three electrode system with table sea salt as an aqueous electrolyte. For a symmetrical solid-state supercapacitor: graphene/PVA-table sea salt/graphene gave a good specific capacitance of 31.67 F g−1 at 0.25 A g−1 with an energy density of 6.33 W h kg−1 at a power density of 600 W kg−1, with good charge–discharge stability, which was 87% after 8000 cycles. Thus, the development of table sea salt as an environmentally friendly electrolyte has a good potential for use in energy storage applications.

MnO2 Nanosheets Decorated MOF-Derived Co3O4 Triangle Nanosheet Arrays for High-Performance Supercapacitors

ABSTRACT In this work, hierarchical Co3O4@MnO2 nanosheet (NS) hybrid nanostructures are grown on carbon cloth by a facile method combining the metal–organic framework (MOF) templating process and electrodeposition. Due to the synergetic effect between Co3O4 triangle NSs and MnO2 NSs and the unique structure with large surface area and numerous channels for ion diffusion, the Co3O4@MnO2 core–shell NS array electrode shows good electrochemical properties with a high specific capacitance of 644.8 F g−1 at a current density of 1 A g−1, remarkable rate capability (capacitance retention of 64.5% at 20 A g−1) and excellent cycle performance (capacitance retention of 91% after 3000 cycles at 5 A g−1). The excellent electrochemical performance makes the Co3O4@MnO2 core–shell NSs promising candidates in supercapacitors.

High-performance asymmetric supercapacitor based on urchin-like cobalt manganese oxide nanoneedles and biomass-derived carbon nanosheet electrode materials

A novel high-performance asymmetric supercapacitor (ASC) has been fabricated based on the cobalt manganese oxide (Co2Mn3O8) nanoneedles as a positive electrode and the hibiscus fruits-based carbon nanosheet (HBFC) as a negative electrode. The Co2Mn3O8 nanoneedles are synthesized by employing a one-step hydrothermal procedure using nickel foam as a support framework for the nanoneedle growth. The Co2Mn3O8 sample shows a distinct urchin-like morphology structure consisting of uniform nanoneedle arrays. The HBFC is prepared by chemical activation of the hibiscus fruits biomass carbon precursor using NH4Cl and KOH activation reagents. The as-prepared Co2Mn3O8 nanoneedles exhibited the highest specific capacity of 238 mAh g−1 at a current density of 1 A g−1. Moreover, the novel Co2Mn3O8//HBFC ASC device assembled based on those electrode materials at a maximum operating potential of 1.7 V shows an excellent energy density of 24.3 Wh kg−1 at a power density of 850 W kg−1. Besides, long-term cycling stability of 91.7% capacitance retention after 10,000 cycles in 2 M KOH electrolyte.

Variation in Capacitive Performance of Poly(3-methylthiophene) Nanosheet Electrodes with Liquid/Semi-Solid/Solid Electrolytes

Variation in Capacitive Performance of Poly(3-methylthiophene) Nanosheet Electrodes with Liquid/Semi-Solid/Solid Electrolytes

High-energy aqueous supercapacitors enabled by N/O codoped carbon nanosheets and “water-in-salt” electrolyte

A facile fabrication strategy is reported to obtain N/O codoped porous carbon nanosheets for purpose of ameliorating the charge transfer and accumulation in the concentrated LiTFSI (lithium bis(trifluoromethane sulfonyl)imide) electrolyte. By tunning the feed ratio of comonomers, the porous nanosheet structure is endowed with a significant ion-adsorption surface area (1630 m2/g) and interconnected hierarchical porosity; meanwhile, high-level N/O dopants (N: 3.58 at%, O: 12.91 at%) increase the effective contact area for electrolyte ions, and further facilitate rapid ion/electron transfer. Benefiting from the advantageous features, carbon nanosheets electrode reveal an enhanced specific capacitance (375 F/g) in three-electrode configuration and the H2SO4-based device yields a high gravimetric energy density of 11.4 Wh/kg. Particularly, the ion-diffusion highways in porous carbon nanosheets contribute to the 2.25 V LiTFSI-based symmetric device with a high energy delivery up to 33.1 Wh/kg. This work offers an inspiring strategy for facile fabrication of carbon nanosheets, and demonstrates their promising application in “water-in-salt” electrolyte-based supercapacitor systems.

Designing PEDOT-modified V6O13 nanosheet arrays for sodium storage

Vanadium oxides, such as V6O[Formula: see text], have a high theoretical capacity for sodium storage, but their performance faces the challenges of low conductivity and poor cycling stability caused by side reactions. To solve these problems, we report on the material design of self-supported nanosheet arrays coated with poly(3, 4-ethylenedioxythiophene) (PEDOT). In this design, the nanosheet architecture facilitates the electron and ion transport to boost the charge storage, while the PEDOT coating prevents the direct contact between the electrode nanosheet and the electrolyte, thus inhibiting the occurrence of side reactions. This PEDOT-modified nanosheet electrode exhibits a reversible capacity of 179 mAh g[Formula: see text] in the potential range of 1.5–3.8 V, and retains 66% of the initial capacity at a rate of 1 C for 100 cycles.

Self-induced matrix with Li-ion storage activity in ultrathin CuMnO2 nanosheets electrode

Conversion anode materials such as Mn3O4 draw much attention due to their considerable theoretical capacity for lithium-ion batteries (LIBs). However, poor conductivity, slow solid-state Li-ion diffusion, and huge volume expansion of the active materials during charge/discharge lead to unsatisfied electrochemical performance. Despite several strategies like nanocrystallization, fabricating hierarchical nanostructures, and introducing a matrix are valid to address these crucial issues, the achieved electrochemical performance still needs to be further enhanced. What is worse, the matrix with less or no Li-ion storage activity may lower the achieved capacity of the electrodes. Herein, ultra-thin CuMnO2 nanosheets with the thickness of 5–8 nm were evaluated for LIBs. The ultra-thin sheet-like nanostructure offers sufficient contact areas with electrolyte and shortens the Li-ion diffusion distance. Moreover, the in-situ generated Mn and Cu along with their oxides could play the role of matrix and conductive agent in turn at different stages, relieving the stress brought by volume expansion. Therefore, the as-prepared ultra-thin CuMnO2 nanosheets electrode displays a remarkable reversible capacity, long cycling stability, and outstanding rate capability (a reversible capacity of 1160.5 mAh g−1 at 0.1A g−1 was retained after 100 cycles with a capacity retention of 95.1 %, and 717.8 mAh g−1 at 2.0 A g−1 after 400 cycles).

Front Cover: Two‐Dimensional Organic/Inorganic Hybrid Nanosheet Electrodes for Enhanced Electrical Conductivity toward Stable and High‐Performance Sodium‐Ion Batteries (ChemSusChem 16/2021)

Front Cover: Two‐Dimensional Organic/Inorganic Hybrid Nanosheet Electrodes for Enhanced Electrical Conductivity toward Stable and High‐Performance Sodium‐Ion Batteries (ChemSusChem 16/2021)