Development of broma-resistant hydrogen oxidation and reduction catalysts in hydrogen brom flow batteries

Renewable energy sources have a volatile and variable nature, such as solar and wind. Storing the energy obtained from these sources using redox flow batteries, which is one of the electrical energy storage systems, enables it to be used when the energy demand is low and helps to balance the energy supply. Hydrogen-Bromine flow cell is a type of flow cell used for energy storage and conversion. In this type of battery, energy is stored and recycled using hydrogen and bromine electrolytes. The bromine electrolyte used in the H2-Br2 flow cell accumulates on the electrode surfaces due to its toxic nature and slows down the electrochemical reactions. This causes the performance of the battery to decrease. Within the scope of this study, two different ratios (15 and 20%) IrNi/C catalysts that can catalyze bromine resistant hydrogen reduction and oxidation reactions were synthesized in order to eliminate the performance degradation caused by bromine. Charge-discharge performance tests of the H2-Br2 flow cell were carried out in order to see the performance effects and reaction catalysis capabilities of the IrNi/C catalyst with 20% and 15% total metal loadings. H2-Br2 flow cell tests were carried out on 20% IrNi/C catalyst by performing surface modification (acidic, acidic+thermal modification) to the anode and cathode electrodes. Performed H2-Br2 flow cell performance tests were compared with 67% Pt/C (Tanaka) catalyst. As a result of the H2-Br2 flow cell discharge performance tests of the synthesized catalyst, it was determined that the 20% IrNi/C catalyst achieved a power density of 0.034 W/cm2 and achieved higher performance than the 15% IrNi/C catalyst. As a result of the surface modifications applied to the electrodes, a current density of 0.129 A/cm2 and a power density of 0.088 W/cm2 were obtained for the anode catalyst loaded with acidic+thermal modified IrNi/C catalyst, and these values are higher than the pure electrode with 67% Pt/C catalyst. In the H2-Br2 charge test, a circuit potential of 1.22 V was reached with the IrNi/C catalyst with an acidic + thermal electrode and a color change was observed between the electrolytes. When the structural characterizations of the synthesized catalyst were examined, it was observed that the IrNi/C structure was formed, the metal loading was successfully carried out at different rates, and the Vulcan-XC72 carbon structure used as the support material was bonded to the iridium and nickel metal structures.