Hybrid Electrode Research Articles

Towards the Reduction of Pt Loading in High Temperature Proton Exchange Membrane Fuel Cells - Effect of Fe-N-C in Pt-Alloy Cathodes.

Pt poisoning by phosphate in high temperature proton exchange membrane fuel cells (HT-PEMFC) leads to loadings up to 1 mgPt cm-2 per electrode of costly materials. While cheaper Fe-N-C catalysts are unaffected by phosphate deactivation and contribute to the catalysis of the oxygen reduction reaction, their volumetric activity is substantially lower. In this study, the effect of Pt-loading reduced hybrid cathodes for HT-PEMFC is investigated using commercial Celtec®-P-based assembling. A promising effect of Fe-N-C incorporation in terms of acid attraction and activity retention is found. A longer activation (230 h, 0.3 A cm-2 ) for the hybrid membrane electrode assembly (MEA) is necessary, due to the slower acid distribution within Fe-N-Cs. This study shows the potential of Pt-content reduction by up to 25 % compared to standard MEA using hybrid electrodes. Moreover, important insights for future strategies of cell activation are revealed for these hybrid MEAs.

Synergetic pseudocapacitive sodium capture for efficient saline water desalination by iron oxide Hydroxide-Decorated palladium nanoparticle anchored 3D flowerlike molybdenum sulfide

Capacitive deionization (CDI)-based saline water desalination presents an admirable alternative for sustainable freshwater production. However, the lack of robust electrode materials impedes its wide application. Herein, a three-dimension (3D) heterostructured iron oxide-hydroxide-incorporated palladium nanoparticle-anchored molybdenum disulphide (FeOOH/Pd/MoS2) hybrid constructed by the two-step spontaneous interfacial redox reactions is reported as efficient Faradaic CDI electrode materials for desalination application. The FeOOH/Pd/MoS2 hybrid electrode delivers a superior desalination capacity of 41.1 mg g−1 in a 500 mg L-1 NaCl solution, along with impressive cycling stability and a high capacitive contribution of 80 % at a rate of 1 mV s−1. The synergetic pseudocapacitive removal process is thoroughly clarified by ex-situ XPS characterizations. Experimental analysis and density functional theory calculations reveal that the bi-component participation of FeOOH and Pd can efficiently tailor the electronic structure of MoS2, leading to the reinforcing electronic conductivity toward the promoted Na+ capture feature. Moreover, the hybrid electrode manifests outstanding removal efficiencies up to 91.25 % for diverse heavy metal ions (i.e., Pb2+, Cd2+, Cu2+, Ni2+, and Cr3+), demonstrating its great prospects for low-concentration wastewater purification. This work supplies an ingenious avenue for the rational design of heterostructured MoS2 Faradaic electrodes for advanced CDI desalination.

N-doped carbon nanotubes with high amount of graphitic nitrogen as an excellent electrocatalyst for water splitting in alkaline solution

Nitrogen-doped carbon nanotubes (NCNTs) containing high amounts of graphitic nitrogen (g-N) deposited on nickel foam (NF) are investigated as catalysts for the hydrogen (HER) and oxygen evolution reaction (OER) in alkaline solution. NCNTs with abundant g-N were synthesised on NF at a low temperature (600 °C) via atmospheric pressure chemical vapor deposition over electrodeposited Fe particles. The physicochemical characteristics of NCNTs@NF hybrid electrodes were investigated by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy and compared to those of graphene@NF, ultrathin graphite@NF, and N-doped graphite@NF. The electrochemical activity towards both the HER and OER on all samples was evaluated by linear sweep voltammetry. Experimental results paired with density functional theory (DFT) calculations revealed the contribution of both the metal substrate and the NCNTs to improve the HER performance. DFT results indicate that NCNTs containing high amounts of g-N are a very promising electrocatalyst for water splitting. Furthermore, this study will motivate a direction for reasonable design defects to improve the electrochemical performance of CNTs and consequently meet the targeted requirement of new clean energy devices.

Evolution of novel nanostructured MoCoFe-based hydroxides composites toward high-performance electrochemical applications: Overall water splitting and supercapacitor

Metal hydroxides are versatile and appealing electrode materials owing to their merits such as easy room-temperature synthesis, nanostructures formation, higher conductivity, crystallite or non-crystallite formation, porous structures, etc. Herein, nanostructured ternary transition metal (M = Mo, Co, Fe) hydroxides (TTMHs) are successfully grown on nickel foams via template-free single-step electrodeposition for overall water splitting and supercapacitor applications. Interestingly, numerous element ratios of Mo5+, Co2+, and Fe3+ in the electrodeposition precursor solutions manifested novel nanostructures viz nanosheets, nanoflakes, nanoparticles, and nanograss-like structures were evolved for different precursor solutions. For water splitting, a negative electrode prepared using aqueous Mo:Co:Fe (4.0:4.0:2.0 M ratio) metal salt solution that exhibited excellent hydrogen evolution activity with 98 mV overpotential, whereas a positive electrode (Mo:Co:Fe = 3.0:3.5:3.5) shows efficient oxygen evolution with 227 mV overpotential, and a full cell assembled from these active electrodes exhibited lower 1.56 V cell voltage at 10 mAcm−2. For the supercapacitor, a working electrode with composition Mo:Co:Fe = 6.0:2.0:2.0 showed 3354.7 mFcm−2 high areal capacitance at 1.0 mAcm−2 with excellent retention (91% after 3000 cycles). An asymmetric supercapacitor (ASC) device was fabricated that exhibited enormous energy and power densities of 1.27 × 10−3 Whcm−3 and 3.75 Wcm−3, respectively. The high-performances of both devices (water splitting full cell and supercapacitor) are due to the unique composition of hybrid electrodes (with nanostructured morphology) and synergistic effects. The present investigation demonstrates a simple strategy for preparing potential TTMHs composite electrodes with the evolution of different morphologies for multiple electrochemical applications.

Development of a polyaniline/CMK-3/hydroquinone composite supercapacitor system

Hybrid supercapacitors are important in energy storage modules owing to their high power density. High-power electrical double-layer capacitor (EDLC) materials are frequently used to host faradaic capacitance materials to maintain a high power density with improved energy density. Herein, a hybrid electrode was developed using ordered mesoporous carbon (CMK-3) as EDLC material and conductive polymer polyaniline (PANi) as faradaic capacitance material. The processing parameters and the synergistic effect of CMK-3 and PANi were determined. Hydroquinone (HQ) was added through charge–discharge in the electrolyte, and its concentration was optimized. The specific capacitance of the PANi/CMK-3/HQ composite system was 684 F/g, whereas those of the PANi/CMK-3 composite, pristine PANi, and CMK3 were 480, 135, and 101 F/g, respectively. The PANi/CMK-3/HQ composite system exhibited excellent cyclic stability, maintaining capacitance retention of 95.45% after 1000 charge–discharge cycles. Finally, the practical applicability of our proposed PANi/CMK-3/HQ composite system was proved with series connected symmetric supercapacitor by powering up the light emitting diodes (LEDs) bulbs for 10 min. The proposed PANi/CMK-3/HQ electrode provides a new route for future supercapacitor design and development.

MOF-derived 3D MnO2@graphene/CNT and Ag@graphene/CNT hybrid electrode materials for dual-ion selective pseudocapacitive deionization

In the present study, an asymmetric pseudocapacitive deionization (PCDI) system was fabricated using redox-active electrode materials of three-dimensional (3D) MnO2@graphene/CNT (MGC) and Ag@graphene/CNT (AGC) as cathode and anode, respectively. The asymmetric PCDI system owns a dual-ion capture mechanism, resulting in a high desalination capacity. The 3D MGC and AGC active electrode materials have been derived through a facile two-step method. Initially, the Mn-BTC and Ag-BTC were in situ grown on the 3D r-GO/CNT structure through a hydrothermal process, yielding Mn-BTC@r-GO/CNT and Ag-BTC@r-GO/CNT hybrids. Subsequently, high-temperature annealing of these hybrids leads to respective MGC and AGC hybrid nanocomposites. Powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analysis facilities were used to investigate the structure and morphology of the as-prepared hybrid nanocomposites. The as-derived 3D MGC and AGC electrode materials exhibit the high specific capacitance of 496.4 and 206.6 F g−1, respectively, at 1 A g−1 using a 1 M NaCl solution. Furthermore, the MGC (cathode)//AGC (anode) electrode pairs-based PCDI system exhibits remarkable desalination performance with a high salt adsorption capacity of 62.4 mg g−1 and a charge efficiency of 95 % in 1000 ppm NaCl solution at 1.2 V.

Synthesis of Synergistic Ni(OH)2@ZnO Core–Shell Nanostructured Electrodes by a Hydrothermal Method and Atomic Layer Deposition for High‐Performance Supercapacitors

A novel nanoporous Ni(OH)2@ZnO core–shell architecture is successfully synthesized via a hydrothermal reaction and atomic layer deposition (ALD). This hybrid material exhibited a well‐defined core–shell nanostructure with high purity and good crystallinity. The conductivity of the electrodes is obviously enhanced by the ALD ZnO thin film. Compared to the conventional Ni(OH)2, the Ni(OH)2 coated with 10 nm of ZnO exhibited significantly enhanced performance, with a maximum specific capacitance value of ≈1,400 F g−1 at a current density of 1 A g−1, which is attributed to the improved charge‐transfer resistance. The asymmetric Ni(OH)2@ZnO//graphene supercapacitor exhibited a good capacitance retention rate and an energy density of 32 Wh kg−1 at a power density of 480 W kg−1, which are higher than those of pure nanostructured Ni(OH)2 and ZnO‐based asymmetric supercapacitors. The remarkable electrochemical performance is contributed to the synergetic presence of the core–shell nanostructure with a high surface area and the highly conductive ZnO films with optimized thickness, which achieve appropriate mass ratio control of the active material. The design of the core–shell architectures demonstrated in this work is expected to be a new and promising approach to ALD for the development of hybrid electrode materials for high‐performance supercapacitor applications.

A self-assembled hybrid electrode for reversible symmetrical solid oxide cells

Reversible Symmetrical Solid Oxide Cell (RSSOC) is a promising energy storage and conversion device with simplified cell configuration and enhanced reliability. However, the compromised activity of the electrodes in reducing and oxidizing atmospheres has restrained the overall performance of RSSOC. In this study, a multifunctional oxide Sr2FeMo0.65Ni0.35O6-δ-Gd0.1Ce0.9O2-δ (SFMN-GDC) developed by a self-assembly method is investigated as the hybrid-electrode to enhance the performance of RSSOC for the first time. The performance of the SFMN-GDC electrode is significantly enhanced with the homogeneous microstructure and extended TPBs length. Moreover, the in situ exsolved Fe-Ni alloy nanoparticle anchored on the SFMN skeleton can further enhance the electrode performance. In SOFC mode operated with H2, the RSSOC with the SFMN-GDC electrode shows a promising peak power density of 0.507 W·cm−2 at 800 °C, while in SOEC mode with 50%CO2–50%H2 at 1.5 V, a current density of 0.803 A·cm−2 is obtained. Most importantly, the RSSOC with SFMN-GDC electrode exhibits excellent stability and cycling reversible operation in both SOFC and SOEC modes for 215 h.

Hierarchical Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate)/Reduced graphene oxide/Polypyrrole hybrid electrode with excellent rate capability and cycling stability for fiber-shaped supercapacitor

Fiber-shaped supercapacitor (FSSC) is considered as a promising energy storage device for wearable electronics due to its high power density and outstanding safety. However, it is still a great challenge to simultaneously achieve high specific capacitance especially at rapid charging/discharging rate and long-term cycling stability of fiber electrode in FSSC for practical application. Here, a ternary poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/reduced graphene oxide/polypyrrole (PEDOT:PSS/rGO/PPy) fiber electrode was constructed by in situ chemical polymerization of pyrrole on hydrothermally-assembled and acid-treated PEDOT:PSS/rGO (PG) hybrid hydrogel fiber. In this case, the porous PG hybrid fiber framework possesses combined advantages of highly-conductive PEDOT and flexible two-dimensional (2D) small-sized rGO sheets, which provides large surface area for the deposition of high-pseudocapacitance PPy, multiscale electrons/ions transport channels for the efficient utilization of active sites, and buffering layers to accommodate the structure change during electrochemical process. Attributed to the synergy, as-obtained ternary fiber electrode presents ultrahigh volumetric/areal specific capacitance (389 F cm−3 at 1 A cm−3 or 983 mF cm−2 at 2.5 mA cm−2) and outstanding rate performance (56 %, 1–20 A cm−3). In addition, 80 % preservation of initial capacitance after 8000 cycles for the corresponding FSSC also illustrates its greatly improved cycle stability compared with 64 % of binary PEDOT:PSS/PPy based counterpart. Accordingly, here proposed strategy promises a new opportunity to develop high-activity and durable electrode materials with potential applications in supercapacitor and beyond.

Design and construction of poly(benzoquinone-diamine)/Ti3C2TX hybrid electrode toward advanced aqueous zinc-ion batteries

Owing to the virtues of low cost, high security, and flexible structure design, zinc-ion batteries (ZIBs) have arisen widespread focus as a rising star in the application of energy-storage devises. Unfortunately, the further advancement of aqueous ZIBs is restricted by the unsatisfactory conduction of electron and structural instability of electrodes. Herein, a new organic-inorganic hybrid material, poly(benzoquinone-diamine)/Ti3C2TX (PBD/Ti3C2TX), has been conceived and fabricated as a cathode of ZIBs for the first time. The abundant CC and CO groups of PBD resulted in improved charge transfer and insolubility, which attributed to various hydrogen bonds and π-π packing interactions. Meanwhile, the Ti3C2TX can improve the electronic conductivity of the hybrid electrode effectively. In addition, the rich functional groups on the surface of Ti3C2TX are propitious to form a tight junction between PBD and Ti3C2TX (such as hydrogen bonds), which is conducive to strengthening the stability of electrode structure. With the synergistic effort of these measures, the PBD/Ti3C2TX composite delivers excellent long-term cycle stability (90 mAh g−1 at 1 A g−1 after 2000 cycles) with high-capacity retention of 78%.

Free‐Standing α‐MoO3/Ti3C2 MXene Hybrid Electrode in Water‐in‐Salt Electrolytes

While transition‐metal oxides such as α‐MoO3 provide high capacity, their use is limited by modest electronic conductivity and electrochemical instability in aqueous electrolytes. Two‐dimensional (2D) MXenes, offer metallic conductivity, but their capacitance is limited in aqueous electrolytes. Insertion of partially solvated cations into Ti3C2 MXene from lithium‐based water‐in‐salt (WIS) electrolytes enables charge storage at positive potentials, allowing a wider potential window and higher capacitance. Herein, we demonstrate that α‐MoO3/Ti3C2 hybrids combine the high capacity of α‐MoO3 and conductivity of Ti3C2 in WIS (19.8 m LiCl) electrolyte in a wide 1.8 V voltage window. Cyclic voltammograms reveal multiple redox peaks from α‐MoO3 in addition to the well‐separated peaks of Ti3C2 in the hybrid electrode. This leads to a higher specific charge and a higher rate capability compared to a carbon and binder containing α‐MoO3 electrode. These results demonstrate that the addition of MXene to less conductive oxides eliminates the need for conductive carbon additives and binders, leads to a larger amount of charge stored, and increases redox capacity at higher rates. In addition, MXene encapsulated α‐MoO3 showed improved electrochemical stability, which was attributed to the suppressed dissolution of α‐MoO3. The work suggests that oxide/MXene hybrids are promising for energy storage.

Enhanced specific capacity and cycling stability of flexible nanocellulose-based pseudocapacitive electrodes by controlled nanostructuring of polyaniline

Flexible, lightweight and electrically conductive composites based on renewable resources have recently attracted a growing interest for the development of high performance sustainable energy storage devices that can meet the needs of modern wearable and portable electronics. Herein, we developed a high performance carbon black@polyaniline (PANI) based flexible electrodes using a facile, low cost and environmentally friendly strategy. The strategy consisted of a co-deposition and nanostructuring of PANI layer with tailored morphology on the surface of carbon black and nanofibrillated cellulose (NFC) via in situ polymerization. NFC acted as a mechanical skeleton and imparted the electrode with strength and flexibility to ensure excellent electrochemical performance. The co-doping of PANI chains via a combination of a primary/secondary dopant, namely, HCl/poly(2-acrylamido-2-methyl-1-propanesulfonic acid), was used to control the morphology of PANI. Correlation between the textural properties of the carbon black, NFC loading, and the properties of the resulting electrodes was established. The maximum specific capacitance of 363±9 F/g at the potential scan rate of 50 mV/s was exhibited by the electrode with 60% of active material loading, for which an effective growth of hierarchical nanostructures of carbon black@PANI on the surface of NFC was achieved, leading to the highest specific surface area of the composite (861 m2/g) and a to a microporosity/mesoporosity balance. The remarkable cycling stability of the hybrid electrodes was attained as the specific capacitance retention was close to 100% with a negligible capacity decay within the tested period (over 500 cycles) regardless of the amount of the active material. This study provides an eco-friendly and cost-effective way to prepare high performance flexible electrodes for pseudo-capacitors

Facile synthesis of microwave-etched Ti3C2 MXene/activated carbon hybrid for lithium-ion battery anode

In this study, we synthesized MXene hybrid electrodes using a novel strategy to generate a synergistic effect between the respective components. Initially, a few-layered Ti3C2 MXene was prepared via microwave-assisted in-situ etching. The AC to Ti3C2 MXene ratio is varied to be 10:0, 9:1, 8:2, and 7:3 in order to maximize electrochemical efficiency. As an anode material for LIBs, the hybrid AC_Ti3C2 (8:2) electrode exhibits the highest initial specific capacity of 1194.2 mAh/g discharged at a current density of 0.2 A/g and maintains over 841.8 mAh/g after 80 consecutive cycles (with a Coulombic efficiency of ∼100 %). An increase in the discharge capacity of the hybrid electrode from 750.5 to 881.9 mAh/g when the current density changed from 1 to 0.2 A/g suggests the excellent rate capability of the AC_Ti3C2 (8:2) hybrid electrode. Furthermore, electrochemical impedance spectroscopic analysis of AC_Ti3C2 (8:2) shows a low charge transfer resistance (Rct) of 8.52 Ω, indicating good conductivity of the hybrid electrode. The work presented here confirms that the AC can be used as an interlayer spacer in synthesizing Ti3C2 MXene hybrids and have excellent application prospects for the next-generation LIBs.

Heterostructures of MXenes and transition metal oxides for supercapacitors: an overview.

MXenes are a large family of two dimensional (2D) materials with high conductivity, redox activity and compositional diversity that have become front-runners in the materials world for a diverse range of energy storage applications. High-performing supercapacitors require electrode materials with high charge storage capabilities, excellent electrical conductivity for fast electron transfer, and the ability of fast charging/discharging with good cyclability. While MXenes show many of these properties, their energy storage capability is limited by a narrow electrochemically stable potential window due to irreversible oxidation under anodic potentials. Although transition metal oxides (TMOs) are often high-capacity materials with high redox activity, their cyclability and poor rate performance are persistent challenges because of their dissolution in aqueous electrolytes and mediocre conductivity. Forming heterostructures of MXenes with TMOs and using hybrid electrodes is a feasible approach to simultaneously increase the charge storage capacity of MXenes and improve the cyclability and rate performance of oxides. MXenes could also act as conductive substrates for the growth of oxides, which could perform as spacers to stop the aggregation of MXene sheets during charging/discharging and help in improving the supercapacitor performance. Moreover, TMOs could increase the interfacial contact between MXene sheets and help in providing short-diffusion ion channels. Hence, MXene/TMO heterostructures are promising for energy storage. This review summarizes the most recent developments in MXene/oxide heterostructures for supercapacitors and highlights the roles of individual components.

High-performance paper-based humidity sensors with Nafion/AgNWs hybrid electrodes.

In the past decade, the development of medical health and human-computer interfaces has put forward requirements for the non-contact application of flexible electronics. Among them, flexible humidity sensors play an important role in the field of non-contact sensing by virtue of their rapid response to humidity changes. In this paper, a flexible paper-based humidity sensor with high performance was fabricated by embedded Au@AgNWs electrodes on filter paper through spraying and electroplating (EP) methods. Benefitting from the moisture-sensitive properties of the paper and the tight integration of the electrodes into the filter paper, the sensor shows the humidity monitoring range of 33-100% RH, large response value of I/I0 = 1958, excellent linearity of R2 = 0.99662 and hysteresis performance under the low excitation voltage of only DC 1 V. In addition, the good biocompatibility of the paper-based humidity sensor endows it with multifunctional applications for breath detection, non-contact applications and food security monitoring. Easy access to raw materials and convenient preparation methods of this work provide new ideas for the development and commercialization of flexible humidity sensors.

Construction of a LiVO3/C core–shell structure for high-rate lithium storage

A LiVO3/C hybrid electrode with a core–shell structure was prepared by a facile two-step synthetic method, and had outstanding lithium-storage performance.

Highly flexible organo-metal halide perovskite solar cells based on silver nanowire-polymer hybrid electrodes.

Flexible perovskite solar cells (FPSCs) have attracted considerable attention due to their broad application possibilities in next generation electronics. However, the commonly used transparent conductive electrodes (TCEs), such as indium tin oxide (ITO), suffer from poor flexible performance, impeding the development of FPSCs. Here, we propose a hybrid electrode (PUA/AgNWs/PH1000) comprising a thin percolation network of silver nanowires (AgNWs) inlaid on the surface of a flexible substrate (PUA) modified with a conductive layer (PH1000), which exhibits high optical transmittance and electrical conductivity, as well as robust mechanical flexibility. By applying the proposed PUA/AgNWs/PH1000 hybrid electrode in FPSCs, the resulting ITO-free devices exhibit the desired flexibility and mechanical stability; it can survive repeated continuous bending cycles and retain 77.4% of its initial power conversion efficiency after 10 000 bending cycles with the bending radius of 5 mm.

Silver nanoparticles - laser induced graphene (Ag NPs - LIG) hybrid electrodes for sensitive electrochemical-surface enhanced Raman spectroscopy (EC-SERS) detection.

This paper presents a novel approach for the fabrication of low cost Electrochemical-Surface Enhanced Raman Scattering (EC-SERS) sensing platforms. Laser Induced Graphene (LIG) electrodes were readily fabricated by direct laser writing of polyimide tapes and functionalized with silver nanoparticles (Ag NPs) to obtain hybrid Ag NPs - LIG electrodes suitable for EC-SERS analysis. Detection was achieved by coupling a handheld potentiostat with a Raman spectrograph, enabling measurement of SERS spectra of target analytes generated during voltage sweeps in the 0.0 to -1.0 V interval range. The sensing capabilities of the fabricated system were first tested with model molecule 4-aminobenzenethiol (4-ABT). Following sensitive detection of 4-ABT, EC-SERS analysis of food contaminant melamine in milk and antibiotic difloxacin hydrochloride (DIF) in river water was demonstrated, achieving sensitive detection of both analytes without pre-treatment steps. The easiness of fabrication, versatility of design, rapid analysis time and potential miniaturization of the system make Ag NPs - LIG electrodes suitable for a large range of in situ applications in the field of food monitoring and for environmental analysis.

Improving electrochemical performance of hybrid electrode materials by a composite of nanocellulose, reduced oxide graphene and polyaniline.

Novel ternary composites of polyaniline (PANI), reduced graphene oxide (RGO), and cellulose nanofibers (CNFs) are prepared by a chemical method for hybrid supercapacitors. CNFs were extracted from sugarcane bagasse waste in sugar production, by physicochemical processes. The composites were investigated as electrode-active materials for hybrid supercapacitors. The obtained results revealed that the presence of RGO and CNFs in the composites led to enhanced electrochemical performances, such as capacitance, rate capability, and long-term cyclability of the composite. The optimal composite of CNFs/RGO/PANI with a weight ratio of 4/16/80 can deliver the highest specific capacitance at 566.2 F g-1 under an applied current of 1 A g-1. After 1000 cycles of repetitive charge and discharge, the optimal composite retains 85.4% of its initial capacitance, whereas the PANI electrode obtained only 36.7% under the same conditions. Moreover, the supercapacitive performance is also strongly dependent on the component of the ternary composites. Overall, the composite is a promising material for hybrid supercapacitors; and the CNF component is a renewable material and a product of waste materials.

Tuning the morphology and size of NiMoO4 nanoparticles anchored on reduced graphene oxide (rGO) nanosheets: The optimized hybrid electrodes for high energy density asymmetric supercapacitors

• Porous NiMoO 4 NPs/rGO composite has been prepared through a facile hydrothermal approach followed by thermal treatment. • NiMoO 4 NPs/rGO composite electrode exhibits high specific capacitance of 2056 Fg -1 and long cyclic stability of 91.4 % after 10,000 cycles. • An asymmetric supercapacitor with high energy density and long cycle life is fabricated. In order to improve the capacitive performance of supercapacitors, NiMoO 4 electrode materials were successfully prepared by a simple and low cost hydrothermal route, and the morphology, microstructure and properties of the materials were successfully optimized by adding reduced graphene oxide (rGO). Electrochemical and sophisticated physical property tests are used to examine the qualities of items. As a supercapacitor electrode material, the NiMoO 4 /rGO composite performed admirably. The specific capacitance reached 2056 Fg -1 at a current density of 2 Ag -1 , which is greater than standard NiMoO 4 at the same current density (788 Fg -1 ). After 1000 charge/discharge cycles, NiMoO 4 /rGO retains 91.1 % of its initial capacitance. NiMoO 4 /rGO composites can be used in asymmetric supercapacitors, and the asymmetric supercapacitor device offers a high power density (60. 2 Whkg -1 ) and energy density (750.5 Whkg -1 ) when used as the positive electrode and activated carbon as the negative electrode. A combination of mesoporous-NiMoO 4 nanoparticles with a high specific surface area and good interaction with conductive rGO is responsible for the improved electrochemical performance of NiMoO 4 /rGO.