GO-modified membranes for vanadium redox flow battery

Graphene oxide (GO) has attracted tremendous attention in membrane-based separation field as it can filter ions and molecules. Recently, GO-based materials have emerged as excellent modifiers for vanadium redox flow battery (VRFB) application. Its high mechanical and chemical stability, nearly frictionless surface, high flexibility, and low cost make GO-based materials as proper materials for the membranes in VRFB. In VRFB, a membrane acts as the key component to determine the performance. Therefore, employing low vanadium ion permeability with excellent stability membrane in vanadium electrolytes is important to ensure high battery performance. Herein, recent progress of GO-modified membranes for VRFB is briefly reviewed. This review begins with current membranes used for VRFB, followed by the challenges faced by the membranes. In addition, the transport mechanism of vanadium ion and the stability properties of GO-modified membranes are also discussed to enlighten the role of GO in the modified membranes

Synthesis and characterization of Sn/Ag nanoparticle composite as electro-catalyst for fuel cell

In this research, Sn/Ag nanoparticle composite was produced by using chemical reduction method with the aids of sodium borohydride as reducing agent and sodium succinate as protective agent. The XRD, EDX, and TEM analyses showed that the Sn/Ag nanoparticle composite was formed with an average particle size of 4.37 + 0.44 nm. For the application, LSV analysis was done on Sn nanoparticle and Sn/Ag nanoparticle composite samples, and the analysis showed current produced from Sn/Ag nanoparticle composite (4.10 × 10-6 A) is higher than Sn nanoparticle (3.47 × 10-6 A) at the potential of -0.83V

Fabrication and evaluation of novel non-enzymatic hydrogen peroxide and glucose sensors based on conducting polymer/nanocomposites / Pooria Moozarm Nia

This research utilized seven novel nanocomposites as non-enzymatic hydrogen peroxide (H2O2) sensor viz. glassy carbon electrode (GCE) as substrate. The composites were prepared with various combinations of polypyrrole (Ppy), reduced graphene oxide (rGO), copper and silver nanoparticles (CuNPs and AgNPs) via different electrodeposition processes. Sensors which were prepared by one-step electrodeposition of rGO-CuNPs and rGO-AgNPs showed a linear detection range up to 18 and 24 mmol.L-1, with LOD of 0.601 and 0.016 μmol.L-1, respectively towards H2O2. Their good performance is attributed to high surface area and synergetic effect of AgNPs and CuNPs with rGO. Polypyrrole was electrodeposited into the composite as a matrix on which nanometals could embed. The investigations revealed the type of dopants is highly effective in morphology and electrocatalytic performance of sensor. Polypyrrole was fabricated layer-by-layer electrodeposition method in the form of nanofiber when lithium perchlorate was used and showed the best performance. The synergetic effect of rGO, AgNPs and PpyNFs made (rGO-AgNPs)/PpyNFs composite an excellent H2O2 sensor with LOD of 1.099 μmol.L-1 with the wide linear range up to 90 mmol.L-1. Layer-by-layer electrodeposition of (rGO/PpyNFs/CuxO) led to a sensor which showed the best electrocatalytic response to H2O2 among all modified electrodes where LOD of 0.030 μmol.L-1 and wide linear range detection up to 100 mmol.L-1 were recorded. This electrode was further tested as amperometric glucose sensor and showed satisfactory performance with detection range of 0.038 μmol.L-1 at the same linear range, which enable it to be used for dual analytes detection. Therefore, along with sensing H2O2, this sensor was used as detector for glucose. To further look into the effect of rGO on sensor performance, PpyMTs-CuNPs and PpyNFs/AgNPs were prepared via one-step and layer-by-layer electrodeposition, respectively in the absence of rGO. PpyMTs-CuNPs electrode showed good response towards H2O2 with LOD of 0.900 μmol.L-1 and linear range up to 110 mmol.L-1, whereas PpyNFs/AgNPs showed good electroreduction response to H2O2 with LOD of 0.115 μmol.L-1 with detection range up to 120 mmol.L-1. It is believed the rGO wrinkle-like morphology was able to increase the surface roughness and consequently acted as an excellent underneath layer. Polypyrrole showed an excellent substrate as a suitable matrix for incorporating nanometals and enhanced speed, sensitivity, selectivity and versatility of the prepared sensors for H2O2 detection. Metal nanoparticles (AgNPs and CuNPs) exhibited a narrow size distribution, enhanced electrocatalytic activity and increased electrocatalytic selectivity with wide linear range and the detection of H2O2 at low potential. These unique properties of the silver and copper nanoparticles could be ascribed to their excellent electron transfer abilities as well as the ultra-high surface area derived from their nanoscale size

Electro-catalytic behavior of silver nanoparticles embedded in potato and tapioca starch for oxygen reduction reaction

The present work demonstrates an eco-friendly and facile method for the synthesis of tapioca and potato starches incorporated by silver nanoparticles hereafter named (T-Ag/NPs) and (P-Ag/NPs), respectively. The analysis of UV–vis showed the appearance of surface plasmon resonance. The TEM analysis shows the formation of highly distributed Ag/NPs with an average diameter and standard deviation of 19.65 ± 2.45 and 12.27 ±7.39 nm for (P-Ag/NPs) and (T-Ag/NPs), respectively. The prepared (T-Ag/NPs) show remarkable potential applicability in energy as low-cost electrode material compared with (P-Ag/NPs). They are used as a non-precious catalyst for oxygen reduction reaction (ORR) in the alkaline medium. The presence of starch promotes long-term stability up to 1000 cycles and avoid the dissolution and agglomeration of silver nanoparticles. The (T-Ag/NPs) show significant stability and reproducibility

Tunable electrochemical approach for reduction of graphene oxide: Taguchi-assisted chemical and structural optimization

The effect of significant parameters on the tuning of electrochemical reduction of graphene oxide (GO) and its electrochemical behavior toward ferri/ferrocyanide as a redox couple was investigated for the first time through a systematic methodical procedure. Reduced graphene oxide (rGOs) modified electrodes were prepared by electrodeposition on the surface of indium tin oxide (ITO) electrode under various GO concentrations, solution pH, scan rate and number of cycles. Taguchi is experimental design method involving orthogonal arrays, signal to-noise (S/N) ratio, analysis of variance (ANOVA) were employed to optimize reaction parameters and to analyze their effects on GO reduction. Cyclic voltammetry (CV) and Fourier-transform infrared spectroscopy (FTIR) analysis revealed that redox activity was least dependent on pH and GO concentrations whereas the use of higher scan rate and lower number of cycles led to more reduction of GO. On the other hand, the electrochemical behavior of samples deposited at higher scan rates totally improved despite the assumption that applying more potential causes more reduction of oxygen functional groups of graphene which are recognized to enhance the electron transfer. Moreover, electrochemical impedance spectroscopy (EIS) showed a lower charge transfer resistance for rGO which was prepared at higher scan rate. Such contrasting finding is precisely discussed in the manuscript to unveil the logical reasons

The optimization of effective parameters for electrodeposition of reduced graphene oxide through taguchi method to evaluate the charge transfer

In the present work, the Taguchi experimental design technique, an effective and elegant tool, is employed to design and optimize a system for improving the quality of the products as well as discovering significant factors and optimize the parameters for electrodeposition of graphene oxide, in order to achieve low charge transfer resistance from the minimum number of experiments. Reduced graphene oxide (rGO) was prepared via electrochemical process. Electrochemical Impedance Spectroscopy was employed to evaluate the effects of variables on charge transfer resistance. Graphene oxide concentration, pH, scan rate and number of cycles were chosen as important effective parameters. Charge transfer resistance was minimized by measuring the signal-to-noise (S/N) ratio of the factors. Analysis of variance (ANOVA) was also employed to monitor the parameter influence and optimize the process

Comparative study on the corrosion and wear behavior of plasma-sprayed vs. high velocity oxygen fuel-sprayed Al8Si20BN ceramic coatings

Corrosion and wear are common problems encountered in the oil and gas industry. These entail the gradual destruction of materials by mechanical action on the opposite surface, and the chemical and/or electrochemical reaction with their environment. In this research, Al8Si20BN ceramic powder with specific properties against corrosion and wear was selected, and it was sprayed with high velocity oxygen fuel (HVOF) and plasma spray methods onto carbon steel substrates. The coatings were characterized with respect to phase composition, microstructure, microhardness and adhesion strength. Their wear behavior was inspected by applying 5, 10, 15 and 20 N loads by pin-on-disc machine, after which the results of both methods were compared. According to the results, the HVOF-coated models were more durable than the plasma-coated models under different loads in the same condition. In addition, the corrosion deterioration of the coated specimens in both brine (3.5% NaCl) and fossil oil were tested for one month (30 days). Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) assessment in 3.5% NaCl solution indicated that the HVOF-sprayed specimens had better corrosion protection than the plasma-sprayed specimens. Generally, the HVOF technique facilitated more durable coats with greater corrosion and tribological resistance compared to the plasma coating technique

Electro-Catalytic Behavior of Silver Nanoparticles Embedded in Potato and Tapioca Starch for Oxygen Reduction Reaction

The present work demonstrates an eco-friendly and facile method for the synthesis of tapioca and potato starches incorporated by silver nanoparticles hereafter named (T-Ag/NPs) and (P-Ag/NPs), respectively. The analysis of UV–vis showed the appearance of surface plasmon resonance. The TEM analysis shows the formation of highly distributed Ag/NPs with an average diameter and standard deviation of 19.65 ± 2.45 and 12.27 ±7.39 nm for (P-Ag/NPs) and (T-Ag/NPs), respectively. The prepared (T-Ag/NPs) show remarkable potential applicability in energy as low-cost electrode material compared with (P-Ag/NPs). They are used as a non-precious catalyst for oxygen reduction reaction (ORR) in the alkaline medium. The presence of starch promotes long-term stability up to 1000 cycles and avoid the dissolution and agglomeration of silver nanoparticles. The (T-Ag/NPs) show significant stability and reproducibility

Self-assembled heteropolyacid on nitrogen-enriched carbon nanofiber for vanadium flow batteries

A novel polyoxometalate-based electrode was developed by incorporating phosphotungstic acid (PWA) in nylon-6,6 nanofiber, followed by carbonization. The developed PWA-carbon nanofiber (PWA-CNF) showed the characteristics of the dual-scale porosity of micro- and mesoporous substrate with surface area of around 684 m2 g-1. The compound exhibited excellent stability in vanadium electrolyte and battery cycling. Evaluation of electrocatalytic properties toward V2+/V3+ and VO2+/VO2 + redox couples indicated promising advantages in electron transfer kinetics and increasing energy efficiency, particularly for the VO2+/VO2 + couple. Moreover, the developed electrode exhibited substantially improved energy efficiency (14% higher than that of pristine carbon felt) in the single cell vanadium redox flow battery. This outstanding performance was attributed to high surface area and abundant oxygen-containing linkages in the developed electrode

Electrocatalytic activity of starch/Fe3O4/zeolite bionanocomposite for oxygen reduction reaction

The present work demonstrated an eco-friendly and facile method for the preparation of starch/Fe3O4/zeolite-bionanocomposite (BNC) at moderate temperature. Zeolite and starch were used as solid support and stabilizer, respectively. The analysis of UV–vis showed the appearance of surface plasmon resonance. From PXRD analysis, the incorporation of magnetite nanoparticles (NPs) in zeolite substrate results in reducing of intensities and broadening of the zeolite peaks of BNC. The TEM analysis showed the formation of highly distributed Fe3O4-NPs with an average diameter and standard deviation of 9.24 ± 3.57 nm. The FESEM and EDX analyses imply that Fe3O4-NPs were homogeneously formed on the surface of the zeolite substrate. VSM analysis illustrated the as prepared BNC possessed magnetic behaviour with a saturation magnetization and coercivity of 1.84 emu g−1 and 17.76 G, respectively. The prepared BNC showed potential applicability in energy as low-cost electrode material. The BNC was used as a non-precious catalyst for oxygen reduction reaction (ORR) in the alkaline medium. The presence of starch and zeolite promoted long term stability up to 1000 cycles and avoid the dissolution and agglomeration of iron oxide. The ORR commences at the onset potential of 0 V follows by the two successive reduction peaks at −0.48 V and −1.00 V