Composite Polybenzimidazole Membrane with High Capacity Retention for Vanadium Redox Flow Batteries

Preparation of Sulfonated Poly(arylene ether)/SiO2 Composite Membranes with Enhanced Proton Selectivity for Vanadium Redox Flow Batteries

Proton exchange membranes (PEMs) are an important type of vanadium redox flow battery (VRFB) separator that play the key role of separating positive and negative electrolytes while transporting protons. In order to lower the vanadium ion permeability and improve the proton selectivity of PEMs for enhancing the Coulombic efficiency of VRFBs, herein, various amounts of nano-sized SiO2 particles were introduced into a previously optimized sulfonated poly(arylene ether) (SPAE) PEMs through the acid-catalyzed sol-gel reaction of tetraethyl orthosilicate (TEOS). The successful incorporation of SiO2 was confirmed by FT-IR spectra. The scanning electron microscopy (SEM) images revealed that the SiO2 particles were well distributed in the SPAE membrane. The ion exchange capacity, water uptake, and swelling ratio of the PEMs were decreased with the increasing amount of SiO2, while the mechanical properties and thermal stability were improved significantly. The proton conductivity was reduced gradually from 93.4 to 76.9 mS cm−1 at room temperature as the loading amount of SiO2 was increased from 0 to 16 wt.%; however, the VO2+ permeability was decreased dramatically after the incorporation of SiO2 and reached a minimum value of 2.57 × 10−12 m2 s−1 at 12 wt.% of SiO2. As a result, the H+/VO2+ selectivity achieved a maximum value of 51.82 S min cm−3 for the composite PEM containing 12 wt.% of SiO2. This study demonstrates that the properties of PEMs can be largely tuned by the introduction of SiO2 with low cost for VRFB applications.

Membrane Assemblies with Soft Protective Layers: Dense and Gel-Type Polybenzimidazole Membranes and Their Use in Vanadium Redox Flow Batteries

Polybenzimidazole (PBI) membranes show excellent chemical stability and low vanadium crossover in vanadium redox flow batteries (VRFBs), but their high resistance is challenging. This work introduces a concept, membrane assemblies of a highly selective 2 µm thin PBI membrane between two 60 µm thick highly conductive PBI gel membranes, which act as soft protective layers against external mechanical forces and astray carbon fibers from the electrode. The soft layers are produced by casting phosphoric acid solutions of commercial PBI powder into membranes and exchanging the absorbed acid into sulfuric acid. A conductivity of 565 mS cm^-1 is achieved. A stability test indicates that gel mPBI and dense PBI-OO have higher stability than dense mPBI and dense py-PBI, and gel/PBI-OO/gel is successfully tested for 1070 cycles (ca. 1000 h) at 100 mA cm^-2 in the VRFB. The initial energy efficiency (EE) for the first 50 cycles is 90.5 ± 0.2%, and after a power outage stabilized at 86.3 ± 0.5% for the following 500 cycles. The initial EE is one of the highest published so far, and the materials cost for a membrane assembly is 12.35 U.S. dollars at a production volume of 5000 m² , which makes these membranes very attractive for commercialization.

Recent Advances in Functional Polymer Materials for Energy, Water, and Biomedical Applications: A Review

Academic research regarding polymeric materials has been of great interest. Likewise, polymer industries are considered as the most familiar petrochemical industries. Despite the valuable and continuous advancements in various polymeric material technologies over the last century, many varieties and advances related to the field of polymer science and engineering still promise a great potential for exciting new applications. Research, development, and industrial support have been the key factors behind the great progress in the field of polymer applications. This work provides insight into the recent energy applications of polymers, including energy storage and production. The study of polymeric materials in the field of enhanced oil recovery and water treatment technologies will be presented and evaluated. In addition, in this review, we wish to emphasize the great importance of various functional polymers as effective adsorbents of organic pollutants from industrial wastewater. Furthermore, recent advances in biomedical applications are reviewed and discussed.

Synergistic Catalysis of SnO2/Reduced Graphene Oxide for VO2+/VO2+ and V2+/V3+ Redox Reactions

In spite of their low cost, high activity, and diversity, metal oxide catalysts have not been widely applied in vanadium redox reactions due to their poor conductivity and low surface area. Herein, SnO₂/reduced graphene oxide (SnO₂/rGO) composite was prepared by a sol–gel method followed by high-temperature carbonization. SnO₂/rGO shows better electrochemical catalysis for both redox reactions of VO²⁺/VO₂⁺ and V²⁺/V³⁺ couples as compared to SnO₂ and graphene oxide. This is attributed to the fact that reduced graphene oxide is employed as carbon support featuring excellent conductivity and a large surface area, which offers fast electron transfer and a large reaction place towards vanadium redox reaction. Moreover, SnO₂ has excellent electrochemical activity and wettability, which also boost the electrochemical kinetics of redox reaction. In brief, the electrochemical properties for vanadium redox reactions are boosted in terms of diffusion, charge transfer, and electron transport processes systematically. Next, SnO₂/rGO can increase the energy storage performance of cells, including higher discharge electrolyte utilization and lower electrochemical polarization. At 150 mA cm⁻², the energy efficiency of a modified cell is 69.8%, which is increased by 5.7% compared with a pristine one. This work provides a promising method to develop composite catalysts of carbon materials and metal oxide for vanadium redox reactions.