Redox flow batteries: from vanadium to earth abundant organic molecules (quinones)
- Autores: Francisco Javier Vázquez Galván
- Directores de la Tesis: Joan Ramon Morante i Lleonart (dir. tes.), Cristina Flox Donoso (dir. tes.)
- Lectura: En la Universitat de Barcelona ( España ) en 2019
- Idioma: español
- Tribunal Calificador de la Tesis: Pere Lluis Cabot Juliá (presid.), Angel Cuadras Tomas (secret.), Francisco José Fernández Carretero (voc.)
- Programa de doctorado: Programa de Doctorado en Nanociencias por la Universidad de Barcelona
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
Along this Thesis dissertation book, which is focused on the topic of Redox Flow Batteries, many efforts have been done in order to improve different aspects of the all-Vanadium Redox Flow batteries (VRFBs) technology, as monitoring each battery compartment, increasing operational temperature range, enhancing negative electrode to reduce side reactions and charge transfer towards V3+/V2+ redox reaction and also modifying positive electrode to obtain a faster VO2+/VO2+ redox reaction. Vanadium technology was chosen over all redox flow technologies due to its mature development reaching the barrier to commercial breakthrough. The main targeted aspects about VRFBs have been:
• Reference electrode implementation into a single cell device (battery) to study separately anolyte and catholyte in real working conditions. This set-up allows following the contribution of each one of the electrodes separately, and consequently knowing the limiting factor in the battery, in order to improve them.
• Electrolyte modifications with catalytic quantities of an additive allowing a larger vanadium ion concentration being able to be solved into the electrolyte, as well as increase the operational temperature window. These improvements are done in order to increase the energy density of the system, and also allow the battery to work in a wider temperature range to adapt this system to broader climate areas without temperature control.
• Electrodes enhancement:
Initially, we will focus our attention into electrode modifications to enhance their electrochemical properties. Firstly, increasing functional groups on the electrode’s surface, which make them more electroactive towards vanadium redox reactions. Secondly, different catalysts are deposited to obtain faster vanadium redox reactions on a carbon-based structure (as graphite felt or carbon felt).
o Anode, main lacks are large ohmic overpotential due to competing side reaction.
- It has been done an exhaust study of different structures of the same material, as it is nanoparticles (NPs), single-nanorods (SNRs) and multi-nanorods assembly (MNRs).
- Graphite and/or carbon felt enhancement using the synthesis of different catalyst (TiO2, TiO2:H, TiO2:iN, O and N groups) which help not only to make the negative redox reaction (V3+/V2+) faster and reduce the voltage drop, but also avoid side reactions (gas evolution) as can be hydrogen evolution reaction (HER). All of these help to elevate the reachable energy and power densities of the battery.
o Cathode, which lacks of a fast kinetics.
- Deposition of a catalyst over graphite felt, as it is ceria (CeO2), to aid the positive redox reaction (VO2+/VO2+) making it faster, as well as improve the efficiencies and accessible capacity of the battery.
Despite the fact that the systems described previously were already proposed several decades ago, they are still the subject of current research. These systems show several inconvenient related to the vanadium abundance, the cost of it, as well as the geopolitical impact caused by its mining. As a consequence, the implementation of organic redox active species is a first step in order to avoid these disadvantages. Organic molecules are abundant, tunable by synthetic pathways and an improved kinetic with the possibility of having two-electron transfer process (as happens to quinones)1,2. Such a battery has the potential to meet the demanding cost, durability, eco-friendliness, and sustainability requirements for grid-scale electrical energy storage.
Furthermore, this system has been studied targeting on a Quinone-based redox flow battery. After the selection of the catholyte (benzoquinone-based molecules as p-benzoquinone, o-benzoquinone and disodium 4,5-dihydroxy-1,3-benzenedisulfonate) and anolyte (Anthraquinone-2,7-disulfonic acid disodium salt) in a methanosulfonic acid solvent, the next step has been improving the electrode technology on both single cell compartments to promote positive and negative redox reactions. In order to do that surface modification has been done, by means of nitrogen and oxygen functionalization using different methods.
Finally, it has been commented the present of all-Vanadium and Aqueous Organic Redox Flow Batteries, as well as some future perspective of both technologies.
