Improving Na+ transport kinetics and Na+ storage of hierarchical rhenium-nickel sulfide (ReS2@NiS2) hollow architecture by assembling layered 2D-3D heterostructures

Mixed metal sulfides have been widely used as anode material of sodium-ion batteries (SIBs) because of their excellent conductivity and sodium ion storage performance. Herein, ReS₂@NiS₂ heterostructures have been triumphantly designed and prepared through anchoring ReS₂ nanosheet arrays on the surface of NiS₂ hollow nanosphere. Specifically, the carbon nanospheres was used as hard template to synthesize NiS₂ hollow spheres as the substrate and then the ultrathin two-dimensional ReS₂ nanosheet arrays were uniformly grown on the surface of NiS₂. The internal hollow property provides sufficient space to relieve the volume expansion, and the outer two-dimensional nanosheet realizes the rapid electron transport and insertion/extraction of Na⁺. Owing to the great improvement of the transport kinetics of Na⁺, NiS₂@ReS₂ heterostructure electrode can achieve a high specific capacity of 400 mAh/g at the high current density of 1 A/g and still maintain a stable cycle stability even after 220 cycles. This hard template method not only paves a new way for the design and construct binary metal sulfide heterostructure electrode materials with outstanding electrochemical performance for Na⁺ batteries but also open up the potential applications of anode materials of SIBs.     

A Superior Na3V2(PO4)3‐Based Nanocomposite Enhanced by Both N‐Doped Coating Carbon and Graphene as the Cathode for Sodium‐Ion Batteries

A superior Na₃V₂(PO₄)₃‐based nanocomposite (NVP/C/rGO) has been successfully developed by a facile carbothermal reduction method using one most‐common chelator, disodium ethylenediamintetraacetate [Na₂(C₁₀H₁₆N₂O₈)], as both sodium and nitrogen‐doped carbon sources for the first time. 2D‐reduced graphene oxide (rGO) nanosheets are also employed as highly conductive additives to facilitate the electrical conductivity and limit the growth of NVP nanoparticles. When used as the cathode material for sodium‐ion batteries, the NVP/C/rGO nanocomposite exhibits the highest discharge capacity, the best high‐rate capabilities and prolonged cycling life compared to the pristine NVP and single‐carbon‐modified NVP/C. Specifically, the 0.1 C discharge capacity delivered by the NVP/C/rGO is 116.8 mAh g^?1, which is obviously higher than 106 and 112.3 mAh g^?1 for the NVP/C and pristine NVP respectively; it can still deliver a specific capacity of about 80 mAh g^?1 even at a high rate up to 30 C; and its capacity decay is as low as 0.0355 % per cycle when cycled at 0.2 C. Furthermore, the electrochemical impedance spectroscopy was also implemented to compare the electrode kinetics of all three NVP‐based cathodes including the apparent Na diffusion coefficients and charge‐transfer resistances.     

A wide potential window aqueous supercapacitor based on LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript>–rGO nanocomposite

Aqueous supercapacitors based on neutral solutions have the advantages of high-ionic conductivity, being environmentally friendly, safe, and low cost. However, the operating potential window for most aqueous electrolytes is far lower than that of organic electrolytes that are commonly used in commercial supercapacitors. In this work, we report on the fabrication of a wide potential window, high-energy aqueous asymmetric supercapacitor, without sacrificing power, by using a nanostructured LiMn₂O₄/reduced graphene oxide (LMO–rGO) nanocomposite. We synthesized the uniformly distributed LMO in the LMO–rGO nanocomposite using a co-precipitation route followed by a low-temperature hydrothermal treatment. In a three-electrode cell setup, the specific capacitance of the LMO–rGO nanocomposite electrode at 1 A/g (1.2 mA/cm²) is 268.75 F/g (258 mF/cm²), which shows a dramatic improvement over the sum of the specific capacitances of pristine LMO (162.5 F/g) and pure rGO (29.94 F/g) electrodes in their relative ratios, when used alone. This finding suggests a synergistic coupling of LMO and rGO in the nanocomposite. We also assembled the LMO–rGO nanocomposite, as the positive electrode, with activated carbon, as the negative electrode, into an asymmetric cell configuration. The device shows an ultra-wide potential window of 2.0 V in a neutral aqueous Li₂SO₄ electrolyte, with a maximum energy density of 29.6 Wh/kg (which approaches the commercial lead-acid batteries), power density of up to 7408 W/kg, and an excellent cycle life (5% loss after 6000 cycles). These findings confirm that an LMO–rGO nanocomposite is a promising material to meet the demands of real world energy storage.     

Cover: Journal of the Chinese Chemical Society 1/2023

In this figure , two allotropes of graphene, graphene oxide and reduced graphene oxide, were synthesized by the modified Hummers' method. Facile synthesis of Sm₂O₃/GO and Sm₂O₃/rGO nanocomposites was carried out via the sol-gel followed by reflux method. Photocatalysis activities got enhanced in Sm₂O₃/rGO as compared to Sm₂O₃/GO nanocomposite and zones of inhibition of antibacterial activities of Sm₂O₃/rGO were found more as compared Sm₂O₃/GO nanocomposite. More details about this figure will be discussed by Prof. Muhammad Akhyar Farrukh and his co-workers on page 32–45 in this issue.

     

Hollow Co9S8 from metal organic framework supported on rGO as electrode material for highly stable supercapacitors

We demonstrate a hydrothermal method to fabricate a composite of reduced graphene oxide (rGO) with hollow Co₉S₈ derived from metal organic framework (MOF), which exhibits a high specific capacitance of 575.9 F/g at 2 A/g and 92.0% capacitance retention after 9000 cycles.     

Reduced graphene oxide supported 2D-NiO nanosheets modified electrode for urea detection

Nickel oxide (NiO) nanosheets (NSs) deposited on different amounts (0.025, 0.05, 0.1, and 0.2 wt%) of reduced graphene oxide (rGO) are synthesized through hydrothermal method. The NiO NSs on rGO (rGO-NiO) are characterized by using X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) analyses, and electrochemical analysis. Electrocatalytic activity of rGO-NiO nanocomposite modified glassy carbon (GC/rGO-NiO) electrode is examined towards electrocatalytic oxidation of urea in 0.1 M NaOH using cyclic voltammetry and amperometry techniques. The GC/rGO_0.1-NiO nanocomposite modified electrode shows enhanced electrocatalytic oxidation of urea than that of other modified electrodes due to the incorporation of NiO NSs on an optimum amount of rGO. The GC/rGO_0.1-NiO modified electrode is used for designing electrochemical sensor for urea, and the detection limit is estimated as 0.47 μM using the amperometry technique. The sensitivity of GC/rGO_0.1-NiO modified electrode is found to be 2450 μA mM⁻¹ cm⁻². In addition to good electroanalytical performance, the present urea sensor displayed good stability and acceptable anti-interference ability in the presence of 20-fold excess concentration of relevant interferents. The GC/rGO_0.1-NiO nanocomposite modified electrode is successfully used for the determination of urea in water sample.

Schematic representation of electrocatalytic oxidation of urea at GC/rGO-NiO nanocomposite modified electrode.

     

A Full Flexible NH4+ Ion Battery Based on the Concentrated Hydrogel Electrolyte for Enhanced Performance

Non-metal ammonium ( ) ions have recently been explored as effective charge carriers in battery systems due to their abundancy, light weight, small hydration shells in water. The research concerning the use of redox chemistry in batteries, particularly in flexible batteries, is still in its infancy. For the first time, we report a flexible full ion battery (AIB) composed of a concentrated hydrogel electrolyte sandwiched between NH₄V₃O₈ ⋅ 2.9H₂O nanobelts cathode and polyaniline (PANI) anode, for enhanced performance. The hydrogel electrolyte is simply synthesized by using ammonium sulfate, xanthan gum and water. As a reference, the AIB based on the liquid aqueous electrolyte is prepared first, which exhibits a capacity of 121 mAh g⁻¹ and a capacity retention of 95 % after 400 cycles at a specific current of 0.1 A g⁻¹. On the other hand, the simple synthesis of the hydrogel electrolyte allows us to facilely tune and optimize the salt contents in the electrolyte, to maximize the ionic conductivity, transport kinetics, mechanical characteristics, and consequently the battery performance. It is found that the flexible battery based on the hydrogel electrolyte prepared from 3 M ammonium sulfate solution shows the best electrochemical performance, i. e., a capacity of 60 mAh g⁻¹ while maintaining a capacity retention of 88 % after 250 cycles at a specific current of 0.1 A g⁻¹. Moreover, the flexible AIB retains excellent electrochemical performance when bent at different angles, demonstrating remarkable mechanical strength and flexibility. Therefore, this study sheds new light on the utilization of concentrated hydrogel electrolyte in the AIB chemistry, for developments of novel electrochemical energy storage technology with high safety and low cost.     

Preparation and characterization of a new CdS–NiFe<Subscript>2</Subscript>O<Subscript>4</Subscript>/reduced graphene oxide photocatalyst and its use for degradation of methylene blue under visible light irradiation

In this paper, CdS nanoparticles as a visible light active photocatalyst were coupled by NiFe₂O₄ and reduced graphene oxide (rGO) to form CdS–NiFe₂O₄/rGO nanocomposite by facile hydrothermal methods. The CdS–NiFe₂O₄/rGO nanocomposite shows enhanced photocatalytic activity for the degradation of methylene blue (MB) under visible light illumination. In addition to improved photocatalytic performance, this prepared nanocomposite shows increased photostability and is magnetically separable from the aqueous media. The degradation rate constant (k_app) of the optimized photocatalyst, i.e. CdS–NiFe₂O₄ (0.05)/rGO 25 wt% nanocomposite, was higher than the corresponding CdS and NiFe₂O₄ nanoparticles by factors of 11.1 and 8.9, respectively. The synergistic interactions between CdS, NiFe₂O₄ and rGO lead to enhanced surface area, reduced aggregation of the nanoparticles, decreased the recombination of photogenerated electron–hole pairs, and increased the charge separation efficiency and effective electron–hole generation transfer. According to the obtained results, a proposed mechanism of the photodegradation of MB under visible light irradiation is finally mentioned.     

Design and green synthesis of 1-(4-ferrocenylbutyl)piperazine chemically grafted reduced graphene oxide for supercapacitor application

In this paper, we report the green synthesis of 1-(4-ferrocenylbutyl)piperazine chemically grafted rGO (P.Fc/rGO) as a battery-type supercapacitor electrode material. For this purpose, initially, the ability of the aqueous Damson fruit extract is investigated in the reduction reaction of graphene oxide (GO). 1-(4-ferrocenylbutyl)piperazine (P.Fc) is synthesized via nucleophilic substitution reaction of piperazine with as-synthesized 4-chlorobutylferrocene. In continue, P. Fc is incorporated to GO by ring-opening reaction of epoxide groups on the GO surface. In the next step, the modified reduction method by aqueous Damson fruit extract was used to prepare the P.Fc/rGO from P.Fc/GO. The prepared materials were characterized by various techniques including FT-IR, Uv–vis, XRD, SEM, EDX, and BET. N₂ adsorption–desorption data of P.Fc/rGO nanocomposite shows that the surface area is 37.746 m² g⁻¹. The capability of P.Fc/rGO nanocomposite for using as an energy storage electrode material in battery-type supercapacitor was examined by investigation of its electrochemical behavior by CV, EIS, and GCD measurements. The charge storage capacity of 1,102 mAh g⁻¹ is achieved at 2.5 A g⁻¹. This nanocomposite shows 89% retention of charge storage capacity after 2000 CV cycles.     

Flower-like Spherical α-Ni(OH)2 Derived NiP2 as Superior Anode Material of Sodium-Ion Batteries

Transition metal phosphides (TMPs) are promising anode candidates for sodium-ion batteries, due to their high theoretical specific capacity and working potential. However, the low conductivity and excessive volume variation of TMPs during insertion/extraction of sodium ions result in a poor rate performance and long-term cycling stability, largely limiting their practical application. In this paper, NiP₂ nanoparticles encapsulated in three-dimensional graphene (NiP₂@rGO) were obtained from the flower-like spherical α-Ni(OH)₂ by phosphating and carbon encapsulation processes. When used as a sodium-ion batteries anode material, the NiP₂@rGO composite shows an excellent cycling performance (117 mA h g⁻¹ at 10 A g⁻¹ after 8000 cycles). The outstanding electrochemical performance of NiP₂@rGO is ascribed to the synergistic effect of the rGO and NiP₂. The rGO wrapped on the NiP₂ nanoparticles build a conductive way, improving ionic and electronic conductivity. The effective combination of NiP₂ nanoparticles with graphene greatly reduces the aggregation and pulverization of NiP₂ nanoparticles during the discharge/charge process. This study may shed light on the construction of high-performance anode materials for sodium-ion batteries and to other electrode materials.     

From nickel oxalate dihydrate microcubes to NiS<Subscript>2</Subscript> nanocubes for high performance supercapacitors

In this study, NiS₂ nanocubes were successfully synthesized by a novel facile solvothermal method using NiC₂O₄·2H₂O microstructures and used as an electrode for high-performance supercapacitors. The electrochemical properties of the prepared NiS₂ electrode were studied using galvanostatic charge–discharge analysis, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) studies. Its maximum specific capacitance was 2077 F g^?1 at a constant current density of about 0.65 A g^?1. Further, the EIS results confirmed the pseudocapacitive nature of the NiS₂ electrode. The experimental results suggested that the NiS₂ electro-active material demonstrates excellent electrochemical performance with high specific capacitance, low resistance, and excellent cycling stability.     

Preparation of reduced graphene oxide/montmorillonite composite hydrogel and its applications for chromium(VI) and organic compounds adsorption

A novel 3D porous reduced graphene oxide/montmorillonite composite hydrogel (rGO–MMT) was prepared by solvent method, where the MMT nanosheets were homogenously dispersed in 3D rGO hydrogel. The porous 3D structure and the high dispersion of MMT nanosheets can promote the adsorption capacity. The effects of MMT content (wt%), the initial concentration of Cr(VI) solution (C0), pH value (pH0), the adsorption dose and temperatures on the adsorption capacity of rGO–MMT for Cr(VI) ions have been investigated. The optimum pH value for Cr(VI) adsorption is 2, and the adsorption capacity increases with MMT content and adsorption temperature. The rGO–MMT composite hydrogel displays the excellent adsorption property for both the heavy metal and organic pollutants. The adsorption capacity of rGO–MMT composite hydrogel is obviously higher than those of single rGO hydrogel and MMT due to the synergistic adsorption of rGO hydrogel and MMT. The adsorption of Cr(VI) ions on the rGO–MMT composite hydrogel follows linear pseudo-second-order kinetics, and the Langmuir model describes the adsorption process much better. Thermodynamic parameters indicate that adsorption is spontaneous, favorable and endothermic in nature.

Graphic abstract

     

Nanocomposites of Sulfonic Polyaniline Nanoarrays on Graphene Nanosheets with an Improved Supercapacitor Performance

A new nanocomposite, poly(aniline‐co‐diphenylamine‐4‐sulfonic acid)/graphene (PANISP/rGO), was prepared by means of an in situ oxidation copolymerization of aniline (ANI) with diphenylamine‐4‐sulfonic acid (SP) in the presence of graphene oxide, followed by the chemical reduction of graphene oxide using hydrazine hydrate as a reductant. The morphology and structure of PANISP/rGO were characterized by field‐emission (FE) SEM, TEM, X‐ray photoelectron spectroscopy (XPS), Raman, FTIR, and UV/Vis spectra. The electrochemical performance was evaluated by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy. The PANISP/rGO nanocomposite showed a nanosized structure, with sulfonic polyaniline nanoarrays coated homogeneously on the surface of graphene nanosheets. This special structure of the nanocomposite also facilitates the enhancement of the electrochemical performance of the electrodes. The PANISP/rGO nanocomposite exhibits a specific supercapacitance up to 1170 F g^?1 at the current density of 0.5 A g^?1. The as‐prepared electrodes show excellent supercapacitive performance because of the synergistic effects between graphene and the sulfonic polyaniline copolymer chains.     

Sulfur-/Nitrogen-Rich Albumen Derived “Self-Doping” Graphene for Sodium-Ion Storage

The development of sodium-ion batteries (SIBs) is hindered by the rapid reduction in reversible capacity of carbon-based anode materials. Outside-in doping of carbon-based anodes has been extensively explored. Nickel and NiS₂ particles embedded in nitrogen and sulfur codoped porous graphene can significantly improve the electrochemical performance. Herein a built-in heteroatom “self-doping” of albumen-derived graphene for sodium storage is reported. The built-in sulfur and nitrogen in albumen act as the doping source during the carbonization of proteins. The sulfur-rich proteins in albumen can also guide the doping and nucleation of nickel sulfide nanoparticles. Additionally, the porous architecture of the carbonized proteins is achieved through removable KCl/NaCl salts (medium) under high-temperature melting conditions. During the carbonization process, nitrogen can also reduce the carbonization temperature of thermally stable carbon materials. In this work, the NS-graphene delivered a specific capacity of 108.3 mAh g⁻¹ after 800 cycles under a constant current density of 500 mA g⁻¹. In contrast, the Ni/NiS₂/NS-graphene maintained a specific capacity of 134.4 mAh g⁻¹; thus the presence of Ni/NiS₂ particles improved the electrochemical performance of the whole composite.     

Synthesis and Electrochemical Performance of Electrostatic Self-Assembled Nano-Silicon@N-Doped Reduced Graphene Oxide/Carbon Nanofibers Composite as Anode Material for Lithium-Ion Batteries

Silicon-carbon nanocomposite materials are widely adopted in the anode of lithium-ion batteries (LIB). However, the lithium ion (Li⁺) transportation is hampered due to the significant accumulation of silicon nanoparticles (Si) and the change in their volume, which leads to decreased battery performance. In an attempt to optimize the electrode structure, we report on a self-assembly synthesis of silicon nanoparticles@nitrogen-doped reduced graphene oxide/carbon nanofiber (Si@N-doped rGO/CNF) composites as potential high-performance anodes for LIB through electrostatic attraction. A large number of vacancies or defects on the graphite plane are generated by N atoms, thus providing transmission channels for Li⁺ and improving the conductivity of the electrode. CNF can maintain the stability of the electrode structure and prevent Si from falling off the electrode. The three-dimensional composite structure of Si, N-doped rGO, and CNF can effectively buffer the volume changes of Si, form a stable solid electrolyte interface (SEI), and shorten the transmission distance of Li⁺ and the electrons, while also providing high conductivity and mechanical stability to the electrode. The Si@N-doped rGO/CNF electrode outperforms the Si@N-doped rGO and Si/rGO/CNF electrodes in cycle performance and rate capability, with a reversible specific capacity reaching 1276.8 mAh/g after 100 cycles and a Coulomb efficiency of 99%.     

Synergetic catalytic effect of rGO,Pd, Fe3O4 and PPy as a magnetically separable and recyclable nanocomposite for coupling reactions in green media

In this paper, rGO/Pd–Fe₃O₄@PPy as an efficient stable nanocomposite was synthesized. To understand the synergetic effects of rGO, Pd, Fe₃O₄ and PolyPyrrole, the performance of rGO/Pd–Fe₃O₄@PPy as a heterogeneous recyclable nanocatalyst in the green synthesis of C‐C and C‐O coupling products, as well as different conditions are studied. Synthesized rGO/Pd–Fe₃O₄@PPy was characterized by FT‐IR, XRD, FE‐SEM, EDS, TGA and AFM analysis. Best results are obtained under sonication in H₂O for C‐C coupling and by ball‐milling for C‐O coupling. The benefits of this method include: green solvents and conditions, absence of external base, low reaction times with high yield and easy work‐up method.     

A novel synthesis of Nb_2O_5@rGO nanocomposite as anode material for superior sodium storage

The development of novel anode materials,with superior rate capability,is of utmost significance for the successful realization of sodium-ion batteries(SIBs).Herein,we present a nanocomposite of Nb_2 O_5 and reduced graphene oxide(rGO) by using hydrothermal-assisted microemulsion route.The water-in-oil microemulsion formed nanoreactors,which restrained the particle size of Nb_2 O_5 and shortened the diffusion length of ions.Moreover,the rGO network prevented agglomeration of Nb_2 O_5 nanoparticles and improved electronic conductivity.Consequently,Nb_2 O_5@rGO nanocomposite is employed as anode material in SIBs,delivering a capacity of 195 mAh/g after 200 charge/discharge cycles at 0.2 A/g.Moreover,owing to conductive rGO network,the Nb_2 O_5@rGO electrode rende red a specific capacity of 76 mAh/g at high current density of 10 A/g and maintained 98 mAh/g after 1000 charge/discharge cycles at 2 A/g.The Nb_2 O_5@rGO electrode material prepared by microemulsion method shows promising possibilities for application of SIBs.     

Design of hierarchical and mesoporous FeF3/rGO hybrids as cathodes for superior lithium-ion batteries

Iron fluoride (FeF₃) is considered as a promising cathode material for Li-ion batteries (LIBs) due to its high theoretical capacity (712 mAh/g) with a 3e^? transfer. Herein, we have designed a strategy of hierarchical and mesoporous FeF₃/rGO hybrids for LIBs, where the hollow FeF₃ nanospheres are the main contributor to the specific capacity and the 2D rGO nanosheets are the matrix elevating the electronic conductivity and buffering the volume expansion. The unique FeF₃/rGO hybrid can be rationally synthesized by a non-aqueous in-situ precipitation method, offering the merits of large specific surface area with rich active sites, fast transport channels for lithium ions, effective alleviation of volume expansion during cycles, and accelerating the electrochemical reaction kinetics. The FeF₃/rGO hybrid electrode possesses a high initial discharge capacity of 553.9 mAh/g at a rate of 0.5 C with 378 mAh/g after 100 cycles, acceptable rate capability with 168 mAh/g at 2 C, and feasible high-temperature operation (320 mAh/g at 70 °C). The superior electrochemical behaviors presented here demonstrates that the FeF₃/rGO hybrid is a potential electrode for LIBs, which may open up a new vision to design high-efficiency energy-storage devices such as LIBs based on transition metal fluorides.     

Self-assembled oligo(phenylene ethynylene)s/graphene nanocomposite with improved electrochemical performances for dopamine determination

In this work, a novel 1,4-bis (4- aminophenylethynyl)benzene (OPE-NH₂, a symmetric linear conjugated oligo(phenylene ethynylene)s derive) and chemically-reduced graphene oxide (rGO) nanocomposite (OPE-NH₂/rGO) was synthesized by a simple self-assembly method. The OPE-NH₂/rGO nanocomposite was stable and water soluble. The formation of OPE-NH₂/rGO nanocomposite was ascribed to the π–π stacking interaction between the conjugated structure of OPE-NH₂ and rGO as well as the electrostatic force between the amino group of OPE-NH₂ and the carboxyl group on rGO, which was characterized by FT-IR, UV–vis spectra and fluorescence spectra. The OPE-NH₂/rGO nanocomposite exhibited significantly improved electrocatalytic activity to the oxidization of dopamine (DA) than that of rGO or OPE-NH₂. The electrochemical performances of OPE-NH₂/rGO were dependent on the OPE-NH₂ contents, and OPE-NH₂ content of 5 wt% exhibited the highest activity. Compared with that of rGO, the nanocomposite presented superior high sensitivity with detection limit of 5 nM, excellent selectivity, wide linear range (0.01–60 μM) and good stability on the determination of DA. The practical application of the developed OPE-NH₂/rGO nanocomposite modified electrode was successfully demonstrated for DA determination in human serum samples.     

Free‐standing and Flexible MoS2/rGO Paper Electrode for Amperometric Detection of Folic Acid

The development of flexible electrodes is of considerable current interest because of the increasing demand for modern electronics, portable medical products, and compact devices. We report a new type of flexible electrochemical sensor fabricated by integrating graphene and MoS₂ nanosheets. A highly flexible and free‐standing conductive MoS₂ nanosheets/reduced graphene oxide (MoS₂/rGO) paper was prepared by a two‐step process: vacuum filtration and chemical reduction treatment. The MoS₂/graphene oxide (MoS₂/GO) paper obtained by a simple filtration method was transformed into MoS₂/rGO paper after a chemical reduction process. The obtained MoS₂/rGO paper was characterized by scanning electron microscopy, X‐ray diffraction spectroscopy, X‐ray photoelectron spectroscopy, Raman spectroscopy, electrochemical impedance spectroscopy. The electrochemical behavior of folic acid (FA) on MoS₂/rGO paper electrode was investigated by cyclic voltammetry and amperometry. Electrochemical experiments indicated that flexible MoS₂/rGO composite paper electrode exhibited excellent electrocatalytic activity toward the FA, which can be attributed to excellent electrical conductivity and high specific surface area of the MoS₂/rGO paper. The resulting biosensor showed highly sensitive amperometric response to FA with a wide linear range.