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Asymmetric supercapacitors (ASCs) with high theoretical energy density have attracted extensive attention during the past years. However, the huge capacity gap between the two electrodes greatly limits high energy density. Regulating electrode mass can make the capacity balanced, while sacrificing weight and volume. Herein, a soluble bipolar molecule, 4‐hydroxy‐2,2,6,6‐tetramethylpiperidinyloxyl (4‐OH‐TEMPO), is proposed as a versatile mediator in the electrolyte to balance the capacity gap in different types of ASCs. 4‐OH‐TEMPO is able to quickly obtain or lose electrons at different potentials regardless of the pH values, thus can contribute large redox capacity at the interface of capacitive electrode in ASCs in both positive or negative electrodes, acidic or alkaline systems. A case study of two typical ACSs is presented, Zn//activated carbon (AC) system with 4‐OH‐TEMPO for positive electrode enhancement in a mildly acidic electrolyte and AC//Ni(OH)2 system with 4‐OH‐TEMPO for negative electrode enhancement in an alkaline electrolyte. Both demonstrate that the addition of 4‐OH‐TEMPO can effectively balance the capacity mismatching between two electrodes, and its capacity contribution can be adjusted by concentration. The energy density of the two ACSs with 4‐OH‐TEMPO can be greatly promoted without significant sacrifice of the device's volume or mass.

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High-salinity wastewater is often difficult to treat by common biological technologies due to salinity stress on the bacterial community. Electricity-assisted anaerobic technologies have significantly enhanced the treatment performance by alleviating the impact of salinity stress on the bacterial community, but electricity-assisted aerobic technologies have less been reported. Herein, a novel bio-electrochemistry system has been designed and operated in which a pair of stainless iron mesh-graphite plate electrodes were installed into a sequencing batch reactor (SBR, designated as S1) to strengthen the performance of saline petrochemical wastewater under aerobic conditions. The removal efficiency of phenol and chemical oxygen demand (COD) in S1 were 94.1 and 91.2%, respectively, on day 45, which was clearly higher than the removal efficiency of a single SBR (S2) and an electrochemical reactor (S3), indicating that a coupling effect existed between the electrochemical process and biodegradation. A certain amount of salinity (≤8000 mg/L) could enhance the treatment performance in S1 but weaken that in S2. Illumina sequencing revealed that microbial communities in S1 on days 45 and 91 were richer and more diverse than in S2, which suggests that electrical stimulation could enhance the diversity and richness of the microbial community, and reduce the negative effect of salinity on the microorganisms and enrich some salt-adapted microorganisms, thus improve the ability of S1 to respond to salinity stress. This novel bio-electrochemistry system was shown to be an alternative technology for the high saline petrochemical wastewater.

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