Synergistic Catalysis of SnO2/Reduced Graphene Oxide for VO2+/VO2+ and V2+/V3+ Redox Reactions

In spite of their low cost, high activity, and diversity, metal oxide catalysts have not been widely applied in vanadium redox reactions due to their poor conductivity and low surface area. Herein, SnO2/reduced graphene oxide (SnO2/rGO) composite was prepared by a sol–gel method followed by high-temperature carbonization. SnO2/rGO shows better electrochemical catalysis for both redox reactions of VO2+/VO2+ and V2+/V3+ couples as compared to SnO2 and graphene oxide. This is attributed to the fact that reduced graphene oxide is employed as carbon support featuring excellent conductivity and a large surface area, which offers fast electron transfer and a large reaction place towards vanadium redox reaction. Moreover, SnO2 has excellent electrochemical activity and wettability, which also boost the electrochemical kinetics of redox reaction. In brief, the electrochemical properties for vanadium redox reactions are boosted in terms of diffusion, charge transfer, and electron transport processes systematically. Next, SnO2/rGO can increase the energy storage performance of cells, including higher discharge electrolyte utilization and lower electrochemical polarization. At 150 mA cm−2, the energy efficiency of a modified cell is 69.8%, which is increased by 5.7% compared with a pristine one. This work provides a promising method to develop composite catalysts of carbon materials and metal oxide for vanadium redox reactions.

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Exploration of reduced graphene oxide microparticles as electrocatalytic materials in vanadium redox flow batteries

10.33774/chemrxiv-2021-qrz1m ◽

2021 ◽

Author(s):

Amira Alazmi ◽

Charles Wan ◽

Pedro Costa ◽

Fikile Brushett

Keyword(s):

Graphene Oxide ◽

Critical Point ◽

Reduced Graphene Oxide ◽

Surface Area ◽

Reaction Rates ◽

Redox Flow Batteries ◽

Reduced Graphene ◽

Critical Point Drying ◽

Flow Batteries ◽

Vanadium Redox

Augmenting reaction rates on porous carbon electrodes is critical for reducing the cost of all-vanadium redox flow batteries (VRFBs). To this end, reduced graphene oxide (rGO) based carbons hold promise, demonstrating high specific surface area, chemomechanical stability, and electrochemical activity. While initial efforts have shown that rGOs can enhance VRFB performance, the range of unique processing conditions leads to a collection of materials with disparate elemental composition and porous structure, thus obscuring performance-determining characteristics behind redox reactions and frustrating the development of generalizable design principles. Here, we generate rGO electrocatalysts of nearly identical chemical composition but different textures (i.e., surface area and pore structure) by varying the drying step in the graphene synthesis (i.e., vacuum-drying vs. carbon dioxide critical point drying). We apply spectroscopic and electrochemical techniques on the synthesized rGOs, observing a three-fold increase in BET surface area using critical point drying. We subsequently decorate carbon felt electrodes – both pristine and thermally activated – with rGO microparticles via a flow deposition procedure, and evaluate their performance and durability in a VRFB cell. The synthesis approach and findings described in this work inform and complement efforts to advance the material science and engineering of rGO electrocatalysts.

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Analysis of the Performance of Phosphorus and Sulphur Co-Doped Reduced Graphene Oxide as Catalyst in Vanadium Redox Flow Battery

Journal of The Electrochemical Society ◽

10.1149/1945-7111/ac49d0 ◽

2022 ◽

Author(s):

Qiang Li ◽

Junnan Wang ◽

Tianyu Zhang ◽

Zinan Wang ◽

Zhichao Xue ◽

...

Keyword(s):

Graphene Oxide ◽

Catalytic Activity ◽

Specific Surface ◽

Reduced Graphene Oxide ◽

Surface Area ◽

Vanadium Redox Flow Battery ◽

Redox Flow Battery ◽

Reduced Graphene ◽

Vanadium Redox ◽

Co Doped

Abstract In a vanadium redox flow battery, the traditional polyacrylonitrile based graphite felt (GF) electrode suffers the problems of low electrochemical catalytic activity and low specific surface area. To improve the performance of the GF electrode, we prepared phosphorus and sulphur co-doped reduced graphene oxide (PS-rGO) as catalyst with the simple treatment of reduced graphene oxide (rGO) in the mixture of phytic acid and sulfuric acid. The GF electrode modified with PS-rGO (PS-rGO-GF) was characterized by scanning electron microscope, specific surface area, X-ray photoelectron spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and charge-discharge tests. The PS-rGO-GF shows enhanced performance toward VO2+/VO2+ redox reaction. The battery with the PS-rGO decorated GF presents an excellent battery performance with the energy efficiency of 81.37 % at the current density of 80 mA cm-2 and the corresponding discharge capacity of 772 mAh due to the high catalytic activity of PS-rGO.

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Reduced Graphene Oxide-Supported Pt-Based Catalysts for PEM Fuel Cells with Enhanced Activity and Stability

Catalysts ◽

10.3390/catal11020256 ◽

2021 ◽

Vol 11 (2) ◽

pp. 256

Author(s):

Irina V. Pushkareva ◽

Artem S. Pushkarev ◽

Valery N. Kalinichenko ◽

Ratibor G. Chumakov ◽

Maksim A. Soloviev ◽

...

Keyword(s):

Graphene Oxide ◽

Reduced Graphene Oxide ◽

Surface Area ◽

Pem Fuel Cells ◽

Polyol Process ◽

Proton Exchange ◽

Active Surface Area ◽

Electrochemical Performances ◽

Simultaneous Reduction ◽

Reduced Graphene

Platinum (Pt)-based electrocatalysts supported by reduced graphene oxide (RGO) were synthesized using two different methods, namely: (i) a conventional two-step polyol process using RGO as the substrate, and (ii) a modified polyol process implicating the simultaneous reduction of a Pt nanoparticle precursor and graphene oxide (GO). The structure, morphology, and electrochemical performances of the obtained Pt/RGO catalysts were studied and compared with a reference Pt/carbon black Vulcan XC-72 (C) sample. It was shown that the Pt/RGO obtained by the optimized simultaneous reduction process had higher Pt utilization and electrochemically active surface area (EASA) values, and a better performance stability. The use of this catalyst at the cathode of a proton exchange membrane fuel cell (PEMFC) led to an increase in its maximum power density of up to 17%, and significantly enhanced its performance especially at high current densities. It is possible to conclude that the optimized synthesis procedure allows for a more uniform distribution of the Pt nanoparticles and ensures better binding of the particles to the surface of the support. The advantages of Pt/RGO synthesized in this way over conventional Pt/C are the high electrical conductivity and specific surface area provided by RGO, as well as a reduction in the percolation limit of the components of the electrocatalytic layer due to the high aspect ratio of RGO.

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Reduced graphene oxide and inorganic nanoparticles composites – synthesis and characterization

Polish Journal of Chemical Technology ◽

10.1515/pjct-2015-0074 ◽

2015 ◽

Vol 17 (4) ◽

pp. 95-103 ◽

Cited By ~ 6

Author(s):

Magdalena Onyszko ◽

Karolina Urbas ◽

Malgorzata Aleksandrzak ◽

Ewa Mijowska

Keyword(s):

Graphene Oxide ◽

Metal Oxide ◽

Reduced Graphene Oxide ◽

Zirconium Dioxide ◽

Water Solution ◽

Metal Oxide Nanoparticles ◽

Direct Synthesis ◽

Inorganic Nanoparticles ◽

Oxide Nanoparticles ◽

Reduced Graphene

Abstract Graphene – novel 2D material, which possesses variety of fascinating properties, can be considered as a convenient support material for the nanoparticles. In this work various methods of synthesis of reduced graphene oxide with metal or metal oxide nanoparticles will be presented. The hydrothermal approach for deposition of platinum, palladium and zirconium dioxide nanoparticles in ethylene glycol/water solution was applied. Here, platinum/reduced graphene oxide (Pt/RGO), palladium/reduced graphene oxide (Pd/RGO) and zirconium dioxide/reduced graphene oxide (ZrO2/RGO) nanocomposites were prepared. Additionally, manganese dioxide/reduced graphene oxide nanocomposite (MnO2/RGO) was synthesized in an oleic-water interface. The obtained nanocomposites were investigated by transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), Raman spectroscopy and thermogravimetric analysis (TGA). The results shows that GO can be successfully used as a template for direct synthesis of metal or metal oxide nanoparticles on its surface with a homogenous distribution.

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