The 6-electron electrochemical reduction of IO₃⁻ to I⁻ represents a breakthrough for the development of next-generation redox flow batteries, offering substantially higher energy densities for oxidizer storage. Our study reveals that on a glassy carbon (GC) electrode in acidic electrolytes, HIO₃ undergoes an autocatalyzed electrochemical reduction to I⁻. This process is mediated by the formation of a thin iodine layer on the electrode, acting as an intermediate and a catalyst. Under steady-state conditions, the iodine layer forms via a comproportionation reaction (HIO₃ + I⁻ + 5H⁺ = I_2 (s) + 3H₂O). Initially, the iodine layer is generated through the slow direct electrochemical reduction of HIO₃ on pristine GC. Once established, this layer significantly enhances the rate of iodate reduction. On voltammetry curves, it is clearly observable as a step-wise current surge to reach a plateau. The limiting current density on the GC seemingly aligns with the Levich equation, varying with the RDE rotation rate. Earlier, we demonstrated the electrochemical oxidation of I⁻ back to HIO₃ using an H₂/HIO₃ flow cell, showcasing a full cycle that underpins the feasibility of this approach for energy storage. This study advances the understanding of iodate electroreduction and underscores its role in enhancing the capacity of next-generation energy storage systems.

Currently, the main type of electrochemical energy storage devices are lithium-ion batteries, the global production of which amounts to billions of units per year. Further progress in electrochemical energy storage systems may follow two general trends: improvement of existing lithium-ion batteries and design of alternative types of energy storage devices (so-called post-lithium-ion batteries). The former trend is limited by the fact that characteristics of lithium-ion batteries are approaching the theoretical limit. The latter one is concerned with sodium-ion batteries, lithium–air batteries and primary power sources, lithium–sulfur batteries, and redox flow systems. The present review analyzes state-of-the-art in the development of virtually all types of electrochemical energy storage devices, which makes it possible to compare their characteristics and determine the most appropriate applications for each type of device. The bibliography includes 316 references.

This work involved the laboratory modeling of biogenic and biogenically mediated corrosion of AISI 304 stainless steel under geochemical conditions representative of the geological disposal of radioactive waste at the Yeniseisky site (Russia). Experiments with a single glucose stimulation of a microbial community sampled from a depth of 450 m established that the initial dominance of organotrophic microflora (primarily genera such as Xanthobacterium, Novosphingobium, Hydrogenophaga, and Pseudomonas) during the first stage (up to 30 days) led to the formation of a microbial biofilm. This biofilm resulted in uniform surface corrosion at a rate of up to 16 µm/year, which is more than 30 times higher than the corrosion rate in the abiotic control. This acceleration is attributed to the accumulation of microbial metabolites, including acetate, ethanol, formate, succinate, n-butyrate, and lactate. The subsequent development of chemotrophic iron- and sulfur-cycling microflora (dominated by genera such as Sideroxydans, Pseudomonas, Geobacter, Desulfuromonas, Desulfovibrio, and Desulfomicrobium) during the second stage of microbial succession (days 60–120) led to the formation of a pit density 10 times greater than that in the abiotic control. It is important to note that the maximum corrosion rates and pit densities were observed upon the addition of a mixture of glucose and sulfate. An assessment of the role of various microbial metabolites and medium components using the potentiodynamic method demonstrated that the combined presence of hydrocarbonate, sulfide, and microbial metabolites in the solution caused a more than fivefold increase in the corrosion current. Thus, the results demonstrate the complex nature of corrosion processes under conditions modeling the geological disposal of radioactive waste, where biological and abiotic factors interact, creating a synergistic effect that significantly enhances corrosion.