The acid-catalyzed desorption of the MDEA CO2-rich liquid under the electrochemical reaction can lower the desorption temperature, thereby reducing the energy consumption for regeneration. In this work, disodium 4,5-dihydroxy-1,3-benzenedisulfonate (tiron) was used as an acidic medium for the electrocatalytic regeneration of the MDEA CO2-rich solution. The results show that the CO2 desorption efficiency reaches more than 90% at 25 °C for the 0.3 M MDEA (0.1 M tiron) system. At 50 °C, compared with 3 M MDEA (without tiron), the maximum CO2 desorption rate and desorption efficiency of the 3 M MDEA (with 0.1 M tiron) CO2-rich solution increased by 27.4 and 18.3%, respectively. Elevating the temperature can increase the quantity of CO2 desorption and the degree of MDEAH+ deprotonation as well as the reactivity of tiron on the electrode, so the desorption rate of CO2 can be further improved by the oxidation of tiron releasing H+ in coordination with thermal desorption.
Redox flow batteries (RFBs) are a promising technology for large-scale energy storage due to their safety, scalability, and design flexibility. This study investigated a tiron-A (4,5-dihydroxybenzene-1,3-disulfonic acid)/tungstosilicic acid (TSA) RFB system, focusing on optimizing the supporting electrolyte and the volumetric ratio of the catholyte (tiron-A) to anolyte (TSA). Electrochemical characteristics, confirmed by CV and EIS, showed that sulfuric acid was the most suitable supporting electrolyte due to its excellent cell potential and lower ohmic resistance compared to sodium chloride and sodium hydroxide electrolytes. To address the inherent electron capacity imbalance between tiron-A (two electrons) and TSA (four electrons), various volumetric ratios were evaluated. The cell with the 3:1 tiron-A:TSA ratio exhibited optimal performance, achieving the highest discharge capacity, excellent cycle stability, and consistent energy efficiency. The electrochemical impedance spectroscopy results revealed that the ohmic resistance was minimized at the 3:1 ratio. This stable, low-ohmic resistance, coupled with a significant reduction in charge transfer resistance after cycling, was confirmed as the dominant factor for the improved long-term performance. These findings demonstrate an effective strategy for developing a high-performance performance tiron-A/TSA RFB system.
Rechargeable aqueous Zn-MnO 2 batteries are promising for large-scale energy storage. A two-electron transfer reaction of MnO 2 /Mn 2+ is available for the cathode, delivering a high theoretical capacity of 616 mAh g −1 . However, this process requires protons, and its practical contribution in conventional mildly acidic zinc batteries is limited. Herein, an organic redox mediator of Tiron is demonstrated to realize dominant two-electron transfer energy storage in MnO 2 cathode materials. The reversible hydroquinone/benzoquinone redox couple of Tiron allows facile spontaneous chemical reaction with MnO 2 to generate Mn 2+ as well as electrochemical redox in zinc cells according to combined in situ/ex situ analysis. Theoretical calculations further reveal that Tiron reduces the energy required for Mn release from the MnO 2 lattice. Therefore, Tiron not only boosts the two-electron reaction of MnO 2 but also reactivates any dead materials. Thanks to these effects, the MnO 2 cathode achieves a high capacity of 525 mAh g −1 at 0.3 A g −1 , far exceeding 384 mAh g −1 in the baseline system. The lifespan also extends four times to 12 000 cycles at 5 A g −1 together with stable capacity retention. This work presents an effective strategy to encourage the high-capacity reaction path of MnO 2 cathodes in aqueous zinc batteries.
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