Characterization of the Chlorine-Hydrogen redox flow battery for electrical energy storage

Abstract

This research focused on the performance of two-phase flow rate reactant cathode electrode to provide advantages due to low pressure of hydrochloric reactant which was sold locally, and safety to use despite an armament property of chlorine gas. The numerical method was used to understand characteristics of methods of the proposed model by simulation with COMSOL and to study the effects of membrane thickness and optimal temperature on the performance of the proton exchange membrane of Redox Flow Battery. The experimental characteristics, including humidity, temperature, current density, flow rate, concentration, electrode synthesis and cell performance, were obtained in operation to validate the numerical results. Hence, the investigation was beneficial as it determined the suitable performance of two-phase flow configuration for the Redox flow battery with low-cost material and helped to understand in depth on the operational characteristics of redox flow battery using hydrochloric acid as a reactant which served as a new model of two-phase flow for cathode. The objectives of the study were as follows: (i) To develop a prototype of redox flow battery using hydrochloric acid as a reactant. (ii) To examine the characteristic and operation of redox flow battery using hydrochloric acid as a reactant including the following parameters: humidity, temperature, current density, flow rate, concentration, membrane synthesis and cell performance.This research study was divided into four parts. The first part focused on cathode's two-phase flow performances of the hydrochloric acid reactant that was affordable,locally sold and provided low-pressure. The experimental characteristics including current density and cathode flow rate were set to 100 - 400 ml/min while the concentration rate was set to 1 - 3 molarity and the reaction area ranged between 25 and 49 cm?. Electrode synthesis and cell performance were obtained in operation to validate the numerical results with comparison between two substances, Pt/C and RuO2. The best performance was achieved at concentration of 2 M and a flow rate of 400 ml/min with a current density and power density exceeding 179 mA/cm2 and 3 mW/om , respectively. The limiting current density and power density for reaction area 49 cm? was about 123 mA/cm2 and 98.1 mW/cm, respectively, at 57.9% voltage efficiency. An increased average voltage efficiency for reaction area 25 cm2 was about 64.5%. The Pt / C side Colleen to RuO2 catalyst loading resulted in decreasing average voltage efficiency (6.6 The second part of research aimed to study the functional groups of active electrocatalysts for the chlorine-side electrode. Catalyst synthesis involved utilizing (RuxCoy)304, Co and Ru contents with different Ru/Co molar ratio of 1:9, 2:8, 3:7, 4:6, 5:5. Conditions of catalytic air furnace temperature ranged from 350 C to 500 *C. The XRD patterns of catalyst samples confirmed the ruthenium oxide and cobalt oxide phases in the products. The EDS spectra detected ruthenium, cobalt and oxygen in the prepared catalysts. The SEM and TEM images showed more dispersion of catalyst ruthenium oxide on cobalt oxide support surface. Characterization using XRD revealed ~57 nm mean diameter of Co3O4 particle sizes, while TEM technique gave ~85.93 nm mean diameter of (Ruo.I Coo9)304 particle size. The test results of catalyst properties using XRD, SEM, EDS, TEM, SAD techniques showed corresponding results. HCI was utilized for RFB by spraying the catalyst material in a range of 0.5-1 M on GDL, the chlorine-side, carbon paper and carbon cloth. With carbon paper that had better discharge voltage efficiency, the 0.5 M treatment generated greatest current density and power density. The catalyst material of 0.5 M on carbon paper created the maximum power density of 19.95 mW/cm2 and current density of 28 mA/cm- at the voltage efficiency of 69.85%. Regarding from the first and second parts of the research, the investigation would be beneficial to determine the suitable performance of two-phase flow configuration for redox flow battery with low-cost materials and to gain in-depth understanding of operation characteristics of a redox flow battery using hydrochloric acid as a reactant for new modeling of two-phase flow in cathode. The third part brought about the development of redox flow battery to replace other types of batteries which worked in a close system, to allow the active substance capable of working for a lifetime while being circulated inside the cell. Due to the ability to increase e power and potential difference performance of the liquid substance, with removable, easy to find, and low-price advantages, hydrochloric acid (HCL) was selected as a reactant used for the redox flow battery in this research. The objective was to study the effects of the optimum temperature of the cathode humidification tank on the performance of redox flow battery. Hydrochloric acid was used as a substrate for testing the humidification tank at temperatures of 5 5 , 6 5 *C and room temperature. The polarization curve was created and the battery redox flow capacity was determined under the optimum operating temperature of the humidification tank. The results showed that for the humidified tank temperature of 65ㆍC, the performance of redox flow battery cells was the highest when it had an electric power of 0.86 watts and a maximum current of 1.35 amperes, resulting in a voltage efficiency of 47.06%. When the standard voltage was 0.6 volts, it was found that the humidification tank temperature of 6 5C provided more power and current at The humidification of the tank compared to 55 'C and the room temperature (0.48, 0.46 watts and 0.75, 0.7 amperes, respectively). The fourth part of research focused on several factors of Proton Exchange Membrane Redox Flow Battery (PEMRFB), one of the most promising energy technologies at the present time. Models of different phenomena occurring in PEMRFB played an important role in this development and performance, which depended on characteristics of the membrane, gas diffusion layer (GDL), catalyst and operating parameters such as operating pressure, cell operation temperature, relative humidity, mass flow rate of feed gases, channel geometries and design of the stack. Recent studies on the compilation of factors affecting durability and performance of PEMRFB indicated that the performance of fuel cell strongly depended on the performance of its membrane. In this research, a three-dimensional PEM Redox Flow Battery model was developed and to investigate the effects of membrane geometry on cell performance. The numerical results indicated that having a thinner membrane corresponded to higher current density, and hydrogen and chlorine consumption in accordance with high hydrochloric production. Finally, the numerical results of the proposed CFD model were compared with the available experimental data which represented good agreement. Redox Flow Battery model was used to analyze operation at a constant temperature and the membrane thickness effect on the performance in a single Redox Flow Battery. According to the three constant temperature of 328,333 and 338 K, it was found that PEMRFB had the highest cell potential at 333 K with a maximum power density of 339.95 mW/cm- and current density of 354.12 mA/cm2. According to the three membrane thicknesses of Nafion 115,117 and 212, Nafion 212 was found to be the best operating thickness for the PEMRFB under the specified inlet operating conditions. At 3330K, the Redox Flow Battery required the optimal relative humidity in the membrane and cathode diffusion layer, which allowed both chlorine and hydrogen proton diffusion to the cathode catalyst layer. The detailed numerical results provided an understanding of the electrochemistry and transport phenomena in a PEM Redox Flow Battery. This model could be used as an effective CFD tool for development aiming to reduce cost for Redox Flow Battery design and optimization.The experimental results in Chapter 3 can answer the two objectives of the study, 1.) To develop a prototype of redox flow battery using hydrochloric acid as a reactant, 2.) To examine characteristics and operation of redox flow battery using hydrochloric acid as a reactant, following these parameters: humidity, temperature, current density, flow rate, concentration, membrane synthesis and cell performance. It was found that 2 M hydrochloric acid together with 400 ml/min flow rate gave the highest efficiency, and using Pt/C catalyst had better performance than RuO2. In Chapter 4, it was found that the synthesized catalyst had the potential as (Ruo. Coo.9)304. Chapter 5 reveals that 65 C is the optimum operating temperature for redox flow batteries. Chapter 6 shows the results of the model indicating that the best performance was obtained at 333K using Nafion 212.