Journal of the Electrochemical Society

WS2/Graphene Composite as Cathode for Rechargeable Aluminum-Dual Ion Battery

2019-11-18T16:31:15+00:00November 18th, 2019|Categories: Publications|Tags: , , |

Tungsten disulfide/graphene nano-sheets (WS2/G) composite is prepared by the ultra-sonication process and applied as a cathode for rechargeable Aluminum-dual ion battery (ADIBs). X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), Fourier transform-infra red spectroscopy (FT-IR) and Raman spectroscopy are used to examine the morphology and architecture of the composite. WS2/G composite displays good electrochemical performance with remarkable specific capacity (152 mA h/g) and good cyclic stability (150 cycles). The aluminum-dual ion intercalation mechanism in the composite is analyzed by XRD, Raman and XPS analysis. WS2/G composite exhibits better electrochemical results than neat WS2, owing to the synergistic effect between highly conductive graphene and WS2.

Published in: "Journal of the Electrochemical Society".

Tyrosinase Incorporated with Au-Pt@SiO2 Nanospheres for Electrochemical Detection of Bisphenol A

2019-08-16T14:38:22+00:00August 16th, 2019|Categories: Publications|Tags: |

Based on tyrosinase modified Au-Pt@SiO2/Au-graphene (APS/Au-GN) electrode, a highly sensitive biosensor was developed for the direct electrochemical detection of bisphenol A (BPA) in food matrices. In this work, Au-graphene (Au-GN), Au-Pt@SiO2 nanocomposites (APS NPs) and tyrosinase (Tyr) were subsequently cast on glass carbon electrode (GCE) via the electrostatic interaction and Van der Waals force. The self-assembled APS NPs and Tyr were decorated on Au-GN forming a new hierarchical three dimensional nanostructure. Due to the dense Au/Pt dots distributed on silica nanoparticles, APS NPs could behave excellent catalytic activity and stability. In this regard, BPA could be sensitively detected by square wave voltammetry (SWV) and differential pulse voltammetry (DPV) with well-defined oxidation peaks at 480 mV and 660 mV, respectively. Under the optimal conditions, SWV detection behaved good analytical performance toward BPA with a wide linear response ranging from 0.01 mg L–1 to10 mg L–1. The detection limit of APS/Au-GN/GCE for BPA was 1.80 μg L–1 (S/N = 3). Moreover, the method showed good reproducibility in practical samples with recoveries from 87.4% to 110.7%, suggesting its potential application in food analysis and safety verification.

Published in: "Journal of the Electrochemical Society".

An Ultrasensitive Electrochemical Sensor Based on Multiwalled Carbon Nanotube@Reduced Graphene Oxide Nanoribbon Composite for Simultaneous Determination of Hydroquinone, Catechol and Resorcinol

2019-08-16T14:38:09+00:00August 16th, 2019|Categories: Publications|Tags: , |

Three dihydroxybenzene isomers, hydroquinone (HQ), catechol (CC) and resorcinol (RS), were determined simultaneously by an ultrasensitive electrochemical sensor based on a glassy carbon electrode modified by multiwalled carbon nanotube@reduced graphene oxide nanoribbon (MWCNT@rGONR) composite. The material was synthesized via hydrothermal method and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). We used cyclic voltammetry (CV) to study the electrochemical performance of the three isomers and differential pulse voltammetry (DPV) to optimize the experimental parameters. Based on the optimal experimental condition, our electrochemical sensor displayed a good linear relationship with the concentration range of 15 to 921 μM, 15 to 1101 μM, and 15 to 1301 μM and detection limit of 3.89 μM, 1.73 μM and 5.77 μM for HQ, CC and RS respectively. The electrochemical sensor based on MWCNT@GONR composite showed outstanding ability of reproducibility, stability and anti-interference. In addition, this sensor was also used successfully for simultaneous determination of HQ, CC and RS in real samples with satisfactory result.

Published in: "Journal of the Electrochemical Society".

Phase Engineering from 2H to 1T-MoS2 for Efficient Ammonia PL Sensor and Electrocatalyst for Hydrogen Evolution Reaction

2019-08-16T14:37:47+00:00August 16th, 2019|Categories: Publications|Tags: , |

In the recent years, phase transitions in MoS2 from 2H to 1T has gained considerable research interest that finds significant technological applications. This paper describes the development of active 1T MoS2 exhibiting metallic behavior from the semiconducting 2H MoS2 by simple two-step hydrothermal method without adding any additional atoms. This strain induced synthesis method allows the modification of the crystal phase and facilitate the electron transfer with reduced resistance of 89 . We studied the formation of 1T MoS2 nanostructures using X-ray diffraction, spectroscopic and microscopic scientific tools. The metallic 1T phase is found to exhibit markedly high optoelectronic properties demonstrating an excitation wavelength dependent down-conversion and up-conversion photoluminescence. The large surface area, tunable bandgap, high electron mobility and increased active sites of 1T MoS2 elucidates a viable designing of optical photoluminescence ammonia sensing. Finally, we investigated the integration of 1T polymorph into an efficient electrocatalytic hydrogen evolution system to compare their catalytic activity with that of 2H MoS2. 1T MoS2 is found to exhibit a low onset potential of 240 mV vs RHE than the 2H phase with a comparatively high onset potential of 550 mV vs RHE. The superior activity of 1T MoS2 owing to the abundant catalytic edge sites are critical for global production of clean and renewable energy sources.

Published in: "Journal of the Electrochemical Society".

A High-Performance Nonenzymatic Urea Sensor Based on Graphene-NiO-Polyaniline

2019-08-16T14:37:07+00:00August 16th, 2019|Categories: Publications|Tags: |

A novel graphene-NiO-polyaniline (Gr-NiO-PANI) was prepared by electrolysis, electrodeposition and electropolymerization methods, respectively. The X-ray diffraction (XRD) proved the successful preparation and composition of the Gr-NiO-PANI hybrid. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to further determine the structure and morphology of as-prepared composites. Cyclic voltammetry confirmed that Gr-NiO-PANI composite had excellent detection effect on urea. By comparing the electrochemical behavior of Gr-NiO-PANI with Gr-NiO and Gr-PANI modified electrodes toward urea, the role of NiO in composite and the detection mechanism of urea were explored. A common linear sweep voltammetry technique was used to detect urea. The test results showed that urea exhibited a good response on the Gr-NiO-PANI modified electrode. In the range of 60~160 μM urea concentration, the response current of the Gr-NiO-PANI modified electrode is proportional to the urea concentration, and the concentration stand curve equation was I(μA) = –0.0886C(μM) + 58.39 (R2 = 0.9917). The as-fabricated sensor exhibited high sensitivity (1.266 μA/μM), lower limit of detection (7.35 μM), excellent reproducibility, and so it can provide a simple and cheap method for detection of urea in environmental monitoring, agriculture, medical industry.

Published in: "Journal of the Electrochemical Society".

Review–Biosensing and Biomedical Applications of Graphene: A Review of Current Progress and Future Prospect

2019-08-16T14:36:56+00:00August 16th, 2019|Categories: Publications|Tags: , |

Graphene has generated widely interest in biosensor study because it had a large surface area, excellent electrical and thermal conductivity, high mechanical strength and other unique physical and chemical properties. In this paper, graphene was reviewed from three aspects. Firstly, several common fabrication methods and characteristics of graphene were introduced. Secondly, applications of the nanosized graphene (NG) and nanosized graphene oxide (NGO) in biosensor and medical imaging were discussed. The NG and NGO had the characteristics of photoluminescence. Based on the fluorescence quenching nature of the graphene surface, the targeting molecules could be confirmed by detecting the fluorescent substance. In addition, the graphene oxide (GO) had a promising prospect in the field of surface-enhanced Raman imaging. In the field of electrochemistry, graphene and its derivatives could be modified on the surface to couple with ligands and antigens and were able to detect specific biomolecules, such as glucose, DNA, proteins and etc. Thirdly, this paper introduced graphene applications in medical treatment. Due to the inherent high near-infrared (NIR) absorbance, graphene materials were widely used in the treatment of in vivo cancer photothermal therapy. The combination of the graphene, anticancer drugs, and specific antigens was highly efficient for drug delivery. This paper summarized the achievements of graphene materials in the medical diagnostics, the presents challenges, and the future prospect.

Published in: "Journal of the Electrochemical Society".

Electrochemical Sensor for the Simultaneous Detection of Guanine and Adenine Based on a PPyox/MWNTs-MoS2 Modified Electrode

2019-08-16T14:36:52+00:00August 16th, 2019|Categories: Publications|Tags: |

Guanine (G) and adenine (A) are two important components of nucleic acid and some small molecules in an organism. In this paper, we developed a new and convenient biosensor for the simultaneous determination of G and A based on overoxidized polypyrrole/multi- walled carbon nanotube and molybdenum disulfide modified glassy carbon electrode (PPyox/ MWNTs-MoS2/GCE). The composite material exhibited remarkable electro-catalytic properties toward the oxidation of G and A due to its large surface area and fast electron transfer. The oxidation peak positions of G and A were at 0.73 V and 1.03 V, respectively, which allowed simultaneous detection of the two substances in coexistence solution. The designed biosensor exhibited linear responses to G and A both in the ranges 5–30 μM and 30–120 μM, with detection limits (S/N = 3) of 1.6 μM (G) and 1.7 μM (A), respectively. Moreover, interferences from some coexisting electro-active species including inorganic ions, glucose, glycine and citric acid were nearly negligible. Further, the sensing strategy was successfully used for the detection of G and A in real samples with satisfactory results, indicating a potential application for the simultaneous electrochemical detection of G and A.

Published in: "Journal of the Electrochemical Society".

Highly Flexible and Durable Graphene Hybrid Film Electrode Modified with Aminated {beta}-Cyclodextrin for Supercapacitor

2019-08-16T14:36:37+00:00August 16th, 2019|Categories: Publications|Tags: , |

The aminated beta-cyclodextrin (β-CD-N) molecules were first used to modify graphene for fabricating the hybrid film electrode (G/β-CD-N) using a method combining mild water bath heat-treatment and vacuum filtration. As compared with pure graphene film (G) and beta-cyclodextrin (β-CD) modified graphene film (G/β-CD), the prepared G/β-CD-N hybrid film exhibits better hydrophilic property, thermal stability and higher mechanical flexibility. Particularly, the G/β-CD-N hybrid film has a remarkably high areal specific capacitance (614 mF cm–2 at 0.5 mA cm–2), good mechanical flexibility (maintaining 98.2% for 1000 bending/unbending cycles) and long-term cycle stability (maintaining 96.8% for 10000 charge/discharge cycles). Moreover, the assembled G/β-CD-N based flexible and symmetric all-solid-state supercapacitor shows an excellent volumetric specific capacitance of 22.53 F cm–3 at 0.5 mA cm–2 and a high energy density of 3.13 mWh cm–3 at a power density of 0.014 W cm–3. The high comprehensive performances of the developed hybrid film electrodes can be ascribed to the combined effects of β-CD molecules and the amination process. This work provides a new approach for the fabrication of flexible supercapacitor with high performance.

Published in: "Journal of the Electrochemical Society".

The Inhibition Mechanism of Lithium Dendrite on Nitrogen-Doped Defective Graphite: The First Principles Studies

2019-08-16T14:36:33+00:00August 16th, 2019|Categories: Publications|Tags: , |

The initial Li-ions nucleation on the basal plane of graphite anode with N-doped defects during the charge progress of lithium-ion battery was investigated theoretically by first-principle calculations using double-layered graphene (DLG) model. Based on the geometric structure optimization, the Li-ions are found to be accumulated on the top surface of N-doped DLG with single vacancy defect (SV-3N) in the near 2D structure. Also for the N-doped DLG with double vacancy defect (DV-4N), the Li-ions are deposit on its top surface, as well as could enter the interlayer space. The electronic analysis proves the ion character of Li layer. Therefore, the initial Li-ions nucleation on the basal plane of graphite with both N-doped SV and DV defects can be suppressed with different detailed mechanisms. The calculation of diffusion energy and lithiation potential shows that the Li-ions nucleation is inhibited via an adsorption-like and intercalation-like process on the DLG with SV-3N and DV-4N, respectively. Additionally, the calculated adsorption energy suggests that more Li atoms are adsorbed due to the presence of N, and thus the capacity of N doped graphite anode can be enhanced accordingly.

Published in: "Journal of the Electrochemical Society".

A Single-Step Electrochemical Preparation of Cadmium Sulfide Anchored ERGO/{beta}-CD Modified Screen-Printed Carbon Electrode for Sensitive and Selective Detection of Nitrite

2019-08-16T14:36:28+00:00August 16th, 2019|Categories: Publications|Tags: , , |

We report a single-step electrochemical process for the preparation of electrochemically reduced graphene oxide/β-cyclodextrin/cadmium sulfide (ERGO/β-CD/CdS) composite on the screen-printed carbon electrode (SPCE). Thereby, the cyclic voltammetry was employed to simultaneously reduce the GO and deposit the CdS from aqueous solutions. This preparation technique was successfully promoted the ERGO/β-CD/CdS on SPCE. The structure and morphology of ERGO/β-CD/CdS were studied by scanning electron microscope (SEM), energy dispersive X-ray (EDX), Raman spectra, FTIR spectra and electrochemical techniques. These techniques are confirmed that the as-deposited material was CdS and it was strongly anchored on ERGO/β-CD. Herein, the β-CD was used to facilitate the strong binding of CdS on RGO/SPCE. This ERGO/β-CD/CdS/SPCE revealed an excellent electrocatalytic activity toward the detection of nitrite when compared with other modified electrodes. The ERGO/β-CD/CdS/SPCE was showed a well-defined oxidation peak for nitrite and also the amperometric responses indicated the sensor has a wide linear range and very low limit of detection 21 nM. These results suggested that the ERGO/β-CD/CdS would be a promising material for the development of electrochemical nitrite sensor and it was successfully applied to the analysis of nitrite in water samples.

Published in: "Journal of the Electrochemical Society".

Ultrasensitive Reduced Graphene Oxide-Poly(Procion)/Gold Nanoparticles Modified Glassy Carbon Electrode for Selective and Simultaneous Determination of Ascorbic Acid, Dopamine, and Uric Acid

2019-08-16T14:36:24+00:00August 16th, 2019|Categories: Publications|Tags: , |

A highly ultrasensitive electrochemical sensor based on electrochemically reduced graphene oxide (ERGO), Procion Red MX-5B (PR) and gold nanoparticles (AuNPs) modified glassy carbon electrode (GCE) was developed. Cyclic voltammetry (CV) was employed to electropolymerize GO-PR mixture on GCE followed by deposition of AuNPs to obtain ERGO-poly(PR)/AuNPs/GCE. The physical properties of the nanocomposite were explored through field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FT-IR). The electrochemical performance of the ERGO-poly(PR)/AuNPs/GCE showed remarkable enhancement in the peak current toward oxidation of AA, DA, and UA with peak potentials separation of 0.21 V for AA-DA, and 0.15 V for DA-UA. Differential pulse voltammetry (DPV) was applied to perform individual and simultaneous analysis of the aforementioned analytes at optimized pH. DPV responses of AA, DA, and UA concentration were obtained over the range of 0.4–110, 0.4–170 and 0.4–150 μM with sensitivities of 0.48, 0.40, and 0.63 μA/μM (S/N = 3), respectively. Limit of detections for AA, DA, and UA were 54, 5.6 and 5.8 nM, respectively. Good repeatability, reproducibility as well as long-term stability were obtained. The developed modified electrode was used successfully to monitor AA, DA, and UA in vitamin C tablets, and human urine samples with favorable recoveries.

Published in: "Journal of the Electrochemical Society".

Effective Electrochemical Determination of Chloramphenicol and Florfenicol Based on Graphene/Copper Phthalocyanine Nanocomposites Modified Glassy Carbon Electrode

2019-08-16T14:36:19+00:00August 16th, 2019|Categories: Publications|Tags: |

In this paper, a highly effective electrochemical sensor based on graphene (Gr)/copper phthalocyanine (CuPc) nanocomposites was successfully designed and achieved. The morphology of Gr/CuPc nanocomposites was characterized by UV-vis, IR, Raman spectra and scanning electron microscopy (SEM). Gr/CuPc nanocomposites were gathered on the surface of the glassy carbon electrode (GCE), and the performence of Gr/CuPc/GCE toward chloramphenicol (CAP) and florfenicol (FF) was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The Gr/CuPc/GCE presented good electrochemical properties, stability, reproducibility, excellent anti-interference ability and satisfying recovery rate in real samples for the detection of CAP and FF. The performance of Gr/CuPc/GCE exhibited a linear ranging from 1.0 x 10–7 to 2.0 x 10–5 M with a detection limit of 2.7 x 10–8 M (–0.652 V vs. Hg/Hg2Cl2, S/N = 3) toward CAP. For FF, it exhibited a linear ranging from 1.0 x 10–6 to 3.0 x 10–5 M with a detection limit of 7.5 x 10–7 M (–0.863 V vs. Hg/Hg2Cl2, S/N = 3). Furthermore, it is for the first time that FF is determined by electrochemical sensor through nanocomposites modified electrode. This proposed electrochemical sensor can provide an opportunity for convenient and reliable determination of CAP or FF.

Published in: "Journal of the Electrochemical Society".

Photoelectrochemical and Non-Enzymatic Glucose Sensor Based on Modified Fehling’s Test by Using Ti/TiO2 NTs-rGO-Cu2O Electrode

2019-08-16T14:36:08+00:00August 16th, 2019|Categories: Publications|Tags: , |

Herein, semiconductor Cu2O/reduced graphene oxide (rGO) coated TiO2 nanotubes (NTs) arrayed titanium foil was used as a photoelectrochemical (PEC) glucose sensor. The concentration of Cu2O nanoparticles (NPs) obtained by Fehling’s solution is directly proportional to glucose amount, and the sensor combined the sensitive feature of PEC analysis and low-cost production of enzymeless sensors with the modified Fehling’s test for the first time. The greatly enhanced photocurrent can be attributed to the p-n heterojunction formation between Cu2O NPs and TiO2 NTs, combined with the excellent conductive rGO, which can simultaneously enhance the charge separation efficiency and facilitate electron transfer. Also, rGO caused Cu2O NPs to cohere with each other on the electrode surface. The wide linear measurement range was found to be 0.0007–20 mM, with a sensitivity of 0.87 μAmM–1 at 0 V vs Ag/AgCl. The proposed nanocomposite can be used for the glucose measurements in beverages.

Published in: "Journal of the Electrochemical Society".

Fabrication of Electro-Active Pt/IMo6O24/Graphene Oxide Nanohybrid Modified Electrode for the Simultaneous Determination of Ascorbic Acid, Dopamine and Uric Acid

2019-08-16T14:36:03+00:00August 16th, 2019|Categories: Publications|Tags: , |

A novel electrochemical active electrode based on isopolyacid ion IMo6O245- (IMo6), Pt and graphene oxide (GO) had been fabricated, which was used as a biosensor in double signal amplification platform for simultaneous detection of ascorbic acid (AA), dopamine (DA) and uric acid (UA). Cyclic voltammetry, amperometry and differential pulse voltammetry indicated that a glass carbon electrode modified with Pt/IMo6/GO (Pt/IMo6/GO-GCE) presented higher electrochemical activity toward the oxidation of AA, DA and UA and faster response than those of a bare GCE, GO-GCE, Pt/GO-GCE and IMo6/GO-GCE. As an electrochemical sensor, the Pt/IMo6/GO-GCE showed a wide linear range of 50–4000 μM, 4–750 μM, and 75–300 μM with the limits of detection (S/N = 3) as 6.4 μM, 0.22 μM and 0.72 μM, corresponding to AA, DA and UA, respectively. In addition, the Pt/IMo6/GO-GCE provided a new option in the simultaneous determination of AA, DA and UA in human blood serum with reliable recovery.

Published in: "Journal of the Electrochemical Society".

Lithium Intercalated-Layered Manganese Oxide and Reduced Graphene Oxide Composite as a Bifunctional Electrocatalyst for ORR and OER

2019-08-16T14:35:54+00:00August 16th, 2019|Categories: Publications|Tags: , |

The bifunctional electrocatalytic activities of birnessite-type layered manganese oxide with lithium ion as an intercalated cation (Li-bir) and its composite with reduced graphene oxide (Li-bir/rGO) toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) were investigated. The enhanced catalytic activity of the Li-bir/rGO composite can be ascribed to the elevated electrical conductivity of the birnessite suggested via a lower charge transfer resistance obtained from the electrochemical impedance spectroscopy. Moreover, the local oxidation states of Mn in the Li-bir/rGO were investigated by in situ X-ray absorption spectroscopy during the ORR and OER processes. Interestingly, the generated oxygen gas from the OER process observed via the in situ gas chromatography of the Li-bir/rGO is 5.44 mmol g–1 which is higher than that of the pristine Li-bir (4.98 mmol g–1). These results suggest that the Li-bir/rGO can be further utilized as a bifunctional electrocatalyst for high-performance metal-air batteries.

Published in: "Journal of the Electrochemical Society".

Easy and Direct Sensing of Toxic Cadmium Using In Situ Bismuth Plating Free Method and Environmentally Friendly Synthesized Graphene Composite

2019-08-16T14:35:48+00:00August 16th, 2019|Categories: Publications|Tags: |

In this study, an environmentally friendly and simple method to synthesize rGO–BiNP nanocomposite was newly developed to address some drawbacks of in-situ Bi plating method for heavy metal ions detection and the synthesized nanocomposite was confirmed using physical and electrochemical analysis. Furthermore, the feasibility of Cd ions detection by the synthesized nanocomposite was confirmed using square-wave anodic stripping voltammetry (SWASV) without in-situ Bi plating, which can change the pH value of test solution and the sensing results. Therefore, the fabricated sensor can directly test target solution without pre-treatment. Under the optimal conditions, the sensitivity for Cd ions was 49 nA/ppb and the correlation coefficient was 0.983, respectively. The limit of detection was 0.3 ppb for Cd ions for a short deposition time of 150 s. The fabricated sensor exhibited linear response to Cd ions in the concentration range from 10 ppb to 120 ppb with good linearity. The determination efficiency toward Cd ions was significantly enhanced by the synthesized rGO–BiNP coated working electrode, due to the enlargement of active area and its electrochemical properties. These results indicate a great potential of the rGO–BiNP electrode for electrochemical heavy-metal ion sensor applications.

Published in: "Journal of the Electrochemical Society".

Polysulfide Reduction and Oxidation at MoS2, WS2 and Cu-Doped MoS2 Thin Film Electrodes

2019-08-16T14:35:43+00:00August 16th, 2019|Categories: Publications|Tags: , , |

The sluggish kinetics of cyclic polysulfide electrochemistry, where sulfur species typically range from S22– to S62–, presents a challenge in several common electrochemical systems. Recently, transition metal dichalcogenides such as WS2 and MoS2 have been proposed for catalysis of polysulfide oxidation-reduction. Here electrodeposited WS2, MoS2, and Cu-doped MoS2 thin films are tested for 24 h cycling in an electrolyte containing 1.8 M Na2Sx + 1.0 M NaOH. Although their initial catalytic activity is high, electrodeposited WS2 films delaminated after ~4 h. The initial catalytic activity of MoS2 films is also high, but MoS2 gradually transforms to Mo2S3 during 24 h of polysulfide oxidation-reduction cycling, as shown by X-ray diffraction (XRD), cross-sectional scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). The best results were obtained for Cu-doped MoS2, which exhibited both high catalytic activity and stable polarization curves during 24 h of potential cycling. To the best of the authors’ knowledge, this is the first report of MoS2 stabilization during cyclic polysulfide electrochemistry through incorporation of a metal dopant into MoS2.

Published in: "Journal of the Electrochemical Society".

Facile Synthesis Gold-Polyindole-Reduced Graphene Oxide Ternary Nanocomposites with Enhanced Electrocatalytic Activity for the Electrochemical Sensing of Caffeine

2019-08-16T14:35:32+00:00August 16th, 2019|Categories: Publications|Tags: , |

An efficient and eco-friendly ultraviolet (UV) irradiation method was developed to synthesize a ternary nanocomposites of gold-polyindole-reduced graphene oxide (Au-PIn-RGO), and as-prepared nanomaterial was then used to fabricate an electrochemical caffeine (CAF) sensor. In the synthesis process, the polymerization of the indole monomer, the reduction of Au3+ ions and GO occurred simultaneously by UV irradiation without using any chemical reagents. The synthesis procedure was simple, inexpensive and green environmentally. Morphology, structure and composition of the Au-PIn-RGO nanocomposites were characterized by various technologies including UV-visible (UV-Vis) spectroscopy, fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Under the optimum conditions, a linear relationship existed between oxidation peak currents and the concentration of CAF in the range of 0.8–40 μM and 40–1000 μM, with a detection limit of 0.26 μM (S/N = 3). The proposed method was successfully applied to determine the CAF in beverages.

Published in: "Journal of the Electrochemical Society".

Synthesis of Fe2O3 Nanoparticle-Decorated N-Doped Reduced Graphene Oxide as an Effective Catalyst for Zn-Air Batteries

2019-08-16T14:35:27+00:00August 16th, 2019|Categories: Publications|Tags: , , |

The advancement of Zn-air batteries requires effective and inexpensive electrocatalysts that facilitate the oxygen reduction reaction (ORR) and evolution reaction (OER). Herein, we report an effective electrocatalyst of Fe2O3 nanoparticle-decorated N-doped reduced graphene oxide (Fe2O3/N-rGO), in which porous Fe2O3 nanoparticles of ~37 nm are anchored on the N-rGO surface uniformly. In an alkaline solution, the synthesized Fe2O3/N-rGO affords superior ORR and OER activity in comparison with Fe2O3 and N-rGO, demonstrating the reinforced synergistic effect. Moreover, it exhibits a comparable limiting current density and a higher current retention ratio in the ORR than commercial Pt/C. A Zn-air battery with Fe2O3/N-rGO delivers a peak power density of 80.1 mW cm–2, and the energy density reaches 730.2 Wh kgZn–1. In addition, stable voltage gaps of ~0.91 V during discharge and charge are achieved at 5 mA cm–2, and the energy efficiency is maintained at ~60% over 120 cycles, illustrating the remarkable stability for rechargeable Zn-air batteries.

Published in: "Journal of the Electrochemical Society".

Editors’ Choice–Methanol Electrooxidation with Platinum Decorated Hematene Nanosheet

2019-08-16T14:35:24+00:00August 16th, 2019|Categories: Publications|

Developing a durable electrocatalyst with a high methanol oxidation reaction activity is highly important for anode design in direct methanol fuel cells. To that end, Pt-hematene sheets have been successfully synthesized by ultrasonic exfoliation followed by a double pulse deposition strategy to adjust the Pt loading. The morphology, structure, and composition of this new class of Pt decorated metal oxide nanosheet have been characterized by transmission electron microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. Electrocatalytic characteristics have been systematically investigated by cyclic voltammetry and compared with commercial Pt/C catalyst. The novel Pt-hematene sheets exhibit a good mass activity with a low peak potential but most of all show an enhanced tolerance to the intermediates of methanol oxidation.

Published in: "Journal of the Electrochemical Society".

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