Family Tree for Aqueous Organic Redox Couples for Redox Flow Battery Electrolytes: A Conceptual Review

Comparison of the Influence of Oxygen Groups Introduced by Graphene Oxide on the Activity of Carbon Felt in Vanadium and Anthraquinone Flow Batteries

An increasing number of studies focus on organic flow batteries (OFBs) as possible substitutes for the vanadium flow battery (VFB), featuring anthraquinone derivatives, such as anthraquinone-2,7-disulfonic acid (2,7-AQDS). VFBs have been postulated as a promising energy storage technology. However, the fluctuating cost of vanadium minerals and risky supply chains have hampered their implementation, while OFBs could be prepared from renewable raw materials. A critical component of flow batteries is the electrode material, which can determine the power density and energy efficiency. Yet, and in contrast to VFBs, studies on electrodes tailored for OFBs are scarce. Hence, in this work, we propose the modification of commercial carbon felts with reduced graphene oxide (rGO) and poly(ethylene glycol) for the 2,7-AQDS redox couple and to preliminarily assess its effects on the efficiency of a 2,7-AQDS/ferrocyanide flow battery. Results are compared to those of a VFB to evaluate if the benefits of the modification are transferable to OFBs. The modification of carbon felts with surface oxygen groups introduced by the presence of rGO enhanced both its hydrophilicity and surface area, favoring the catalytic activity toward VFB and OFB reactions. The results are promising, given the improved behavior of the modified electrodes. Parallels are established between the electrodes of both FB technologies.

Zinc-Bromine Batteries: Challenges, Prospective Solutions, and Future

Zinc-bromine batteries (ZBBs) have recently gained significant attention as inexpensive and safer alternatives to potentially flammable lithium-ion batteries. Zn metal is relatively stable in aqueous electrolytes, making ZBBs safer and easier to handle. However, Zn metal anodes are still affected by several issues, including dendrite growth, Zn dissolution, and the crossover of Br species from cathodes to corrode anodes, resulting in self-discharge and fast performance fading. Similarly, Br2 undergoes sluggish redox reactions on cathodes, which brings several issues such as poor reaction kinetics, the highly corrosive nature of Br species leading to corrosion of separators and poisoning of anodes, and the volatile nature of Br species causing increased internal pressures, etc. These issues are compounded in flowless ZBB configuration as no fresh electrolyte is available to provide extra/fresh reaction species. In this review, the factors controlling the performance of ZBBs in flow and flowless configurations are thoroughly reviewed, along with the status of ZBBs in the commercial sector. The review also summarizes various novel methodologies to mitigate these challenges and presents research areas for future studies. In summary, this review will offer a perspective on the historical evolution, recent advancements, and prospects of ZBBs.

Sulfonate-Based Triazine Multiple-Electron Anolyte for Aqueous Organic Flow Batteries

A new highly soluble triazine derivative (SPr)34TpyTz showing three reversible redox processes with fast kinetics and high diffusion coefficients has been synthesized using an efficient, low-cost, and straightforward synthetic route. Concentrated single cell tests and DFT studies reveal a tendency of the reduced triazine species to form aggregates which could be avoided by tuning the supporting electrolyte concentration. Under the right conditions, (SPr)34TpyTz shows no capacity decay and good Coulombic, voltage, and energy efficiencies for the storage of two electrons. The storage of further electrons leads to a higher capacity decay and an increase of the electrolyte pH, suggesting the irreversible protonation of the generated species. So, a plausible mechanism has been proposed. A higher concentration of (SPr)34TpyTz shows slightly higher capacity decay and lower efficiencies due to the aggregate formation.

Development and Future Scope of Renewable Energy and Energy Storage Systems

 This review study attempts to summarize available energy storage systems in order to accelerate the adoption of renewable energy. Inefficient energy storage systems have been shown to function as a deterrent to the implementation of sustainable development. It is therefore critical to conduct a thorough examination of existing and soon-to-be-developed energy storage technologies. Various scholarly publications in the fields of energy storage systems and renewable energy have been reviewed and summarized. Data and themes have been further highlighted with the use of appropriate figures and tables. Case studies and examples of major projects have also been researched to gain a better understanding of the energy storage technologies evaluated. An insightful analysis of present energy storage technologies and other possible innovations have been discovered with the use of suitable literature review and illustrations. This report also emphasizes the critical necessity for an efficient storage system if renewable energy is to be widely adopted. 

Potential application of metallacarboranes as internal reference: An electrochemical comparative study to ferrocene

Ferrocene and its derivatives have been extensively used as internal reference in electrochemical processes. Yet, they possess limitations such as solvent restrictions that require chemical modifications. In this regard, we...