Ternary transition metal chalcogenides decorated on rGO as an efficient nanocatalyst towards urea electro-oxidation reaction for biofuel cell application

A ternary transition metal chalcogenide, containing MoS2, NiS, and Co3S4 (MCNS), and MCNS/reduced graphene oxide (MCNS/rGO) composite were prepared as anode catalysts by a simple hydrothermal process for Urea electro-oxidation. It's expected that rGO with high specific surface area provides superior catalytic performance for MCNS/rGO than MCNS. Also, the synergic effect of Mo, Ni, and Co in the composite accelerates the urea oxidation and enhances the performance of the catalyst. The composites were characterized by field emission electron microscopy, transition electron microscopy, and X-ray diffraction spectroscopy. Electrochemical properties of composites were evaluated by cyclic voltammetry. The MCNS/rGO demonstrated superior electrocatalytic performance than the MCNS catalyst. The incorporating of rGO into MCNS creates a high electrochemical surface area for urea electro-oxidation that resulted in a higher current density (18 mA cm�2) than MCNS (3.7 mA cm�2) at the presence of 0.6 M urea and the scan rate of 20 mV s�1. The maximum current density obtained 43 mA cm�2 for MCNS/rGO at the scan rate of 70 mV s�1 in room temperature. Also, single cells based on MCNS and MCNS/rGO supplied a maximum power density of 7.7 mW cm�2 and 21.0 mW cm�2 at room temperature, respectively. Hence, MCNS/rGO can be a favorable electrocatalyst for application in the direct urea fuel cell. © 2019 Elsevier B.V

NiO-Co3O4-rGO as an Efficient Electrode Material for Supercapacitors and Direct Alcoholic Fuel Cells

Transition metal oxides can be performant electrode materials for supercapacitors and alcohol oxidation if their conductivity and capacity are improved. Herein, an advanced nanocomposite material made of NiO-Co3O4 on reduced graphene oxide (rGO) is synthesized by a one-step hydrothermal method for supercapacitors and methanol/ethanol oxidation. It is demonstrated that the nanocomposite is a promising material for energy storage as NiO-Co3O4-rGO supercapacitor electrodes achieve a specific capacity of 149 mAh g−1 (894 F g−1) at a current density of 0.5 A g−1, the discharge time of 689 s, and excellent stability of 95% after 6000 cycles. Moreover, NiO-Co3O4-rGO shows a current density of 15 and 10 mA cm−2 in methanol and ethanol oxidation reactions, respectively, along with excellent stability

A remarkable three-component RuO2-MnCo2O4/rGO nanocatalyst towards methanol electrooxidation

A three-part nano-catalyst including ruthenium oxide, manganese cobalt oxide, and reduced graphene oxide nanosheet in form of RuO2-MnCo2O4/rGO is synthesized by one-step hydrothermal synthesis. The material is placed on a glassy carbon electrode (GCE) for electrochemical studies. The ability of these nano-catalysts in the oxidation process of methanol in an alkaline medium for usage in direct methanol fuel cells (DMFC) was examined with electrochemical tests of cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS). The effect of the addition of rGO to the nanocatalyst structure in the methanol oxidation reaction (MOR) process was investigated. We introduced the RuO2-MnCo2O4/rGO as a nanocatalyst with excellent cyclic stability of 97% after 5000 cycles in the MOR process. Besides, the study of the Tafel plots and the effect of temperature and scan rate in the MOR process showed that RuO2-MnCo2O4/rGO nanocatalyst has better electrochemical properties than MnCo2O4 and RuO2-MnCo2O4. This high electrocatalytic activity could be related to the synergistic effect of placement of metal oxides of ruthenium, manganese, and cobalt near each other and putting them on rGO, which enhances conductivity and surface area and improve electron transfer. The decrease in the resistance against charge transfer and the increment in the anodic current density illustrated that the reaction rate is enhanced at higher temperature. Thus RuO2-MnCo2O4/rGO shows robust stability and superior performance for MOR

Hierarchical nanostructures of MgCo2O4 on reduced graphene oxide as a high-performance catalyst for methanol electro-oxidation

A flower-like binary transition metal oxide, in the form of MgCo2O4, was successfully synthesized and investigated by XRD and Raman spectroscopy as well as by SEM and TEM micrographs. A hybrid of MgCo2O4 with reduced graphene oxide (rGO) was prepared to distinguish between the rGO-riched and rGO-free catalysts for potential applications in direct methanol fuel cell (DMFC) anodes (methanol electro-oxidation process). The synergetic effect due to the proximity of magnesium and cobalt oxides, along with their hybridization on the rGO, makes MgCo2O4-rGO an efficient and low-cost catalyst for an anode electrode in the DMFC applications. EIS, CV, LSV tests, and cyclic stability of MgCo2O4-rGO for 2000 subsequent CV cycles confirm the pivotal role of rGO in the catalyst structure. Finally, the single-cell test indicated the suitability of our proposed catalyst for practical applications of DMFC. Indeed, the single-cell polarization diagrams show a significantly improved power density for single cells with MgCo2O4-rGO-based anode (19 mW cm−2) compared to MgCo2O4- based anode (11 mW cm−2)

Hierarchical nanostructures of MgCo2O4 on reduced graphene oxide as a high-performance catalyst for methanol electro-oxidation

A flower-like binary transition metal oxide, in the form of MgCo2O4, was successfully synthesized and investigated by XRD and Raman spectroscopy as well as by SEM and TEM micrographs. A hybrid of MgCo2O4 with reduced graphene oxide (rGO) was prepared to distinguish between the rGO-riched and rGO-free catalysts for potential applications in direct methanol fuel cell (DMFC) anodes (methanol electro-oxidation process). The synergetic effect due to the proximity of magnesium and cobalt oxides, along with their hybridization on the rGO, makes MgCo2O4-rGO an efficient and low-cost catalyst for an anode electrode in the DMFC applications. EIS, CV, LSV tests, and cyclic stability of MgCo2O4-rGO for 2000 subsequent CV cycles confirm the pivotal role of rGO in the catalyst structure. Finally, the single-cell test indicated the suitability of our proposed catalyst for practical applications of DMFC. Indeed, the single-cell polarization diagrams show a significantly improved power density for single cells with MgCo2O4-rGO-based anode (19 mW cm�2) compared to MgCo2O4- based anode (11 mW cm�2). © 2021 Elsevier Ltd and Techna Group S.r.l

Green Synthesis of Zeolitic Imidazolate Frameworks: A Review of Their Characterization and Industrial and Medical Applications

Metal organic frameworks (MOF) are a class of hybrid networks of supramolecular solid materials comprising a large number of inorganic and organic linkers, all bound to metal ions in a well-organized fashion. Zeolitic imidazolate frameworks (ZIFs) are a sub-group of MOFs with imidazole as an organic linker to metals; it is rich in carbon, nitrogen, and transition metals. ZIFs combine the classical zeolite characteristics of thermal and chemical stability with pore-size tunability and the rich topological diversity of MOFs. Due to the energy crisis and the existence of organic solvents that lead to environmental hazards, considerable research efforts have been devoted to devising clean and sustainable synthesis routes for ZIFs to reduce the environmental impact of their preparation. Green chemistry is the key to sustainable development, as it will lead to new solutions to existing problems. Moreover, it will present opportunities for new processes and products and, at its heart, is scientific and technological innovation. The green chemistry approach seeks to redesign the materials that make up the basis of our society and our economy, including the materials that generate, store, and transport our energy, in ways that are benign for humans and the environment and that possess intrinsic sustainability. This study covers the principles of green chemistry as used in designing strategies for synthesizing greener, less toxic ZIFs the consume less energy to produce. First, the necessity of green methods in today’s society, their replacement of the usual non-green methods and their benefits are discussed; then, various methods for the green synthesis of ZIF compounds, such as hydrothermally, ionothermally, and by the electrospray technique, are considered. These methods use the least harmful and toxic substances, especially concerning organic solvents, and are also more economical. When a compound is synthesized by a green method, a question arises as to whether these compounds can replace the same compounds as synthesized by non-green methods. For example, is the thermal stability of these compounds (which is one of the most important features of ZIFs) preserved? Therefore, after studying the methods of identifying these compounds, in the last part, there is an in-depth discussion on the various applications of these green-synthesized compounds