Modulated Zn Deposition by Glass Fiber Interlayers for Enhanced Cycling Stability of Zn–Br Redox Flow Batteries

The zinc bromine redox flow battery (ZBB) is one of the most promising candidates for next-generation energy storage systems due to its low cost, inflammability, and high power and energy densities. However, dendritic Zn growth, which intensifies at higher current densities and larger deposition capacities, practically hinders the high-current and high-capacity operation of ZBBs. Herein, we demonstrate that a non-conductive, highly porous, and zincophilic glass fiber (GF) layer on top of a carbon felt electrode notably suppresses dendritic Zn growth. The ZBB with the GF layer successfully operates for more than 4000 cycles at 80 mA cm–2 and 20 mA h cm–2, in contrast to the cell failure outcome at the 45th cycle for a GF-free ZBB. Electrochemical analysis and simulations suggest that the surface polar groups of the GF facilitate Zn ion transport and matrix-guided Zn deposition. A GF layer decorated with negatively charged polymer achieves highly superior uniform Zn deposition and remarkable cycling stability at 200 mA cm–2 and 50 mA h cm–2, verifying the validity of this approach

Contact Problems of IrO_<i>x</i> Anodes in Polymer Electrolyte Membrane Water Electrolysis

Green-hydrogen production by polymer electrolyte membrane water electrolysis (PEMWE) is limited by the use of expensive Ir-based catalysts, presenting a key challenge in achieving a low-IrOx-loaded membrane electrode assembly (MEA). Here, we investigate the abnormally poor performance and large high-frequency impedances in the ultralow-IrOx-loaded MEA (as low as 0.07 mg cm–2) for PEMWE. We reveal that these primarily originate from the electron transport problem in the native oxide on the Ti porous transport layer (PTL). Based on the metal–insulator band model, we conclude that the upward band bending by the Schottky contact with the high-work-function IrOx and the pinch-off effect by massive ionomer contact are the major causes of electron conductivity loss of the Ti oxide. This study highlights the importance of the catalyst/PTL interface and reveals that modulation of the catalyst work function and ionomer distribution is necessary to achieve high-performing but cheap water electrolysis

Pore-Size-Tuned Graphene Oxide Frameworks as Ion-Selective and Protective Layers on Hydrocarbon Membranes for Vanadium Redox-Flow Batteries

The laminated structure of graphene oxide (GO) membranes provides exceptional ion-separation properties due to the regular interlayer spacing (<i>d</i>) between laminate layers. However, a larger effective pore size of the laminate immersed in water (∼11.1 Å) than the hydrated diameter of vanadium ions (>6.0 Å) prevents its use in vanadium redox-flow batteries (VRFB). In this work, we report an ion-selective graphene oxide framework (GOF) with a <i>d</i> tuned by cross-linking the GO nanosheets. Its effective pore size (∼5.9 Å) excludes vanadium ions by size but allows proton conduction. The GOF membrane is employed as a protective layer to address the poor chemical stability of sulfonated poly­(arylene ether sulfone) (SPAES) membranes against VO₂⁺ in VRFB. By effectively blocking vanadium ions, the GOF/SPAES membrane exhibits vanadium-ion permeability 4.2 times lower and a durability 5 times longer than that of the pristine SPAES membrane. Moreover, the VRFB with the GOF/SPAES membrane achieves an energy efficiency of 89% at 80 mA cm^–2 and a capacity retention of 88% even after 400 cycles, far exceeding results for Nafion 115 and demonstrating its practical applicability for VRFB