Coupling the two-electron water oxidation reaction and two-electron oxygen reduction reaction to ensure the concurrent production of H 2 O 2 can remarkably improve its current efficiency and production rate, which is the bottleneck for H 2 O 2 electrosynthesis. However, ion crossover between cathode and anode chambers may significantly restrain two-electron water oxidation reaction and two-electron oxygen reduction reaction. Herein, we report a zero anion crossover system for simultaneous production of H 2 O 2 enables an outstanding overall current efficiency of 156% and a high generation rate of 385 µmol min –1 . The substantially improved performance is resulted from confining the essential anions (e.g., HO 2 – ) for two-electron oxygen reduction reaction in the cathode and maintaining the high activity of CO 3 2− mediator for two-electron water oxidation reaction in the anode. This work underscores the importance of ion crossover in paired electrochemical synthesis cells and provides a practical approach to developing a highly efficient electrogeneration system for H 2 O 2 .
Chao Deng,Xiaoxin Li,Mustafa Kemal Bayazit,Barun Kumar Chakrabarti,Guo-Ming Weng
The polysulfide/iodide flow battery is a promising candidate for large-scale energy storage systems, but the technology suffers from a notably low Coulombic efficiency. This phenomenon arises because the crossover of hydroxide ions triggers the disproportionation reaction of I3– ions in the posolyte. To mitigate these issues, a middle chamber filled with Na2SO4 solution is created between two cation-exchange membranes to separate the posolyte and negolyte chambers of the PSIFB, thereby constructing a trichamber reactor. This middle chamber can serve as a reservoir for the cross-transportation OH– ions during charge-discharge processes, thereby minimizing their adverse effects on the posolyte. Experimental results reveal that the introduction of the middle chamber leads to a 97.3% reduction in the concentration of OH– ions within the posolyte. Furthermore, finite element analysis demonstrates that the trichamber configuration significantly reduces the flux of OH– ions entering the posolyte, achieving levels even lower than half of those in the dual-chamber structure. This innovative architecture markedly enhances the Coulombic efficiency from approximately 78% in the dual-chamber structure to around 91% in the trichamber structure with a high-concentration electrolyte (4 M NaI and 3 M Na2S2), while concurrently sustaining a highly competitive energy density of 20.05 W h Lposolyte+negolyte–1 at 75% state-of-charge. These findings demonstrate an effective strategy for improving the performance of the polysulfide/iodide flow battery through OH– management, showing potential for developing more efficient flow battery systems for renewable energy storage applications
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