Functionalized graphene oxide for efficient capacitive deionization

ENERCHEM

Novel infiltration method of membranes over activated carbons electrodes

A novel method to modify activated carbons electrodes through addiction of selective ion exchange membrane (IEM) is presented. Nowadays the preferred method to modify an electrode in an electric double layer supercapacitor is to apply a stand-alone membrane in proximity of the electrode itself. This technique produces some drawbacks in terms of dimensions of the device, increase of the internal series resistance and reduction of the total capacitance. With the present method it is possible to use the membrane with a conformal contact with the electrode or directly in the production of the slurry. In particular the first approach studied consists into melting the membrane and casting and drying it under vacuum over activated carbons. This drying process, is performed in a glass oven B-585 from BÜCHI. In this way it is possible to reduce internal resistance of the device, providing good ion selectivity and maintaining a high capacitance. The second approach consists in exploiting the IEM as polymeric functional binder inside the slurry. It is possible to exploit the long chains of ion exchange polymers to bind activated carbons together and onto the substrate. This strategy allows the substitution of common binders like PVDF, with several benefits in terms of reduced electrical resistance, tunable surface charge of the electrodes, reduced cost and increased sustainability

Functionalized graphene oxide for efficient capacitive deionization

ENERCHEM

Performance study on the addition of novel functionalized graphene oxide in activated carbon-based electrodes for capacitive deionization

Graphene oxide (GO) and its reduced and functionalized forms have been attracting the interest of the scientific community. Widely studied for its unique properties, GO finds applications in the vast and heterogenous scenario of various research fields. When focusing on porous electrodes for capacitive applications, GO is commonly proposed in its reduced form (rGO) for improved electrical conductivity. Specifically, designed functionalization procedures are also used to tune the charges spontaneously present on the surface of GO. In this context, this work reports on the investigation of few novel functionalized GO materials proposed for capacitive deionization application. The modification of the GO has been pursued following different strategies in order to achieve a controlled tuning of the surface charge of the GO. The functionalized materials have been widely characterized by means of morphological, physico-chemical and electrochemical characterization techniques. Finally, the materials have been mixed with activated carbons and coated onto metallic current collectors to assemble a device for capacitive deionization application. Performances of the different materials have been compared in terms of salt adsorption and charge efficiency, proving the beneficial effect of the presence of functionalized GO. Interestingly, the same approach and materials can also be applied for the case of aqueous supercapacitors, since they share many features and similar working mechanism with capacitive deionization

Performance study on the addition of novel functionalized graphene oxide in activated carbon-based electrodes for capacitive deionization

Graphene oxide (GO) and its reduced and functionalized forms have been attracting the interest of the scientific community. Widely studied for its unique properties, GO finds applications in the vast and heterogenous scenario of various research fields. When focusing on porous electrodes for capacitive applications, GO is commonly proposed in its reduced form (rGO) for improved electrical conductivity. Specifically, designed functionalization procedures are also used to tune the charges spontaneously present on the surface of GO. In this context, this work reports on the investigation of few novel functionalized GO materials proposed for capacitive deionization application. The modification of the GO has been pursued following different strategies in order to achieve a controlled tuning of the surface charge of the GO. The functionalized materials have been widely characterized by means of morphological, physico-chemical and electrochemical characterization techniques. Finally, the materials have been mixed with activated carbons and coated onto metallic current collectors to assemble a device for capacitive deionization application. Performances of the different materials have been compared in terms of salt adsorption and charge efficiency, proving the beneficial effect of the presence of functionalized GO. Interestingly, the same approach and materials can also be applied for the case of aqueous supercapacitors, since they share many features and similar working mechanism with capacitive deionization

Green Methods for the Fabrication of Graphene Oxide Membranes: From Graphite to Membranes

Graphene oxide (GO) has shown great potential as a membrane material due to its unique properties, including high mechanical strength, excellent thermal stability, versatility, tunability, and outperforming molecular sieving capabilities. GO membranes can be used in a wide range of applications, such as water treatment, gas separation, and biological applications. However, the large-scale production of GO membranes currently relies on energy-intensive chemical methods that use hazardous chemicals, leading to safety and environmental concerns. Therefore, more sustainable and greener approaches to GO membrane production are needed. In this review, several strategies proposed so far are analyzed, including a discussion on the use of eco-friendly solvents, green reducing agents, and alternative fabrication techniques, both for the preparation of the GO powders and their assembly in membrane form. The characteristics of these approaches aiming to reduce the environmental impact of GO membrane production while maintaining the performance, functionality, and scalability of the membrane are evaluated. In this context, the purpose of this work is to shed light on green and sustainable routes for GO membranes’ production. Indeed, the development of green approaches for GO membrane production is crucial to ensure its sustainability and promote its widespread use in various industrial application fields

Performance study of a thin film cation exchange membrane on carbon electrode for supercapacitor application

In this work we report a green procedure for the infiltration of a SPEEK solution into a porous carbon electrode resulting in a thin-film cation exchange membrane. The electrodes have been investigated by a morphological point of view, showing the formation of a thin coating infiltrated into the porous carbonaceous matrix, while mechanical peeling of a tape demonstrated the adhesion of the proposed layer. The fabricated electrodes have been analyzed by electrochemical measurement. The 3-electrode cyclic voltammetry measurements allowed to verify the voltage window resulting in an improved negative potential, while the electrochemical impedance spectroscopy showed a reduction of the electrical resistance. The SPEEK electrode was used in a supercapacitor and deeply characterized by electrochemical analysis. The reported findings demonstrate for the first time the possibility to exploit a cation exchange material in thin film configuration for supercapacitor application with improved performance of the device and exclusively involving the use of nontoxic reagents

Crown-Ether Functionalized Graphene Oxide Membrane for Lithium Recovery from Water

The massive worldwide transition of the transport sector to electric vehicles has dramatically increased the demand for lithium. Lithium recovery by means of ion sieves or supramolecular chemistry has been extensively studied in recent years as a viable alternative approach to the most common extraction processes. Graphene oxide (GO) has also already been proven to be an excellent candidate for water treatment and other membrane related applications. Herein, a nanocomposite 12-crown-4-ether functionalized GO membrane for lithium recovery by means of pressure filtration is proposed. GO flakes were via carbodiimide esterification, then a polymeric binder was added to improve the mechanical properties. The membrane was then obtained and tested on a polymeric support in a dead-end pressure setup under nitrogen gas to speed up the lithium recovery. Morphological and physico-chemical characterizations were carried out using pristine GO and functionalized GO membranes for comparison with the nanocomposite. The lithium selectivity was proven by both the conductance and ICP mass measurements on different sets of feed and stripping solutions filtrated (LiCl/HCl and other chloride salts/HCl). The membrane proposed showed promising properties in low concentrated solutions (7 mg(Li)/L) with an average lithium uptake of 5 mg(Li)/g in under half an hour of filtration time