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Electrochemically exfoliated graphene (EEG) with different levels of doping, electrical conductivity, and sheet size was synthesized with a one-step method and the resulting EEGs were incorporated in a poly(vinyl alcohol) (PVA) matrix via a simple solution-casting approach to prepare high-performance dielectrics. To maximize the EEG potential for making the nanocapacitor structure and minimizing the dielectric loss, we developed an aligned nanofiller structure. The aligned codoped EEG (as nanoelectrodes in the nanocapacitor structure, at 4.0 wt %) in the PVA matrix (as nanodielectric in the nanocapacitor structure) led to a high dielectric constant (203) and low dielectric loss (0.2) in X-band frequency. The chemical and structural characteristics of the nanocomposite account for the enhanced dielectric properties: (i) good dispersion of codoped EEG (nitrogen and sulfur doped) in the polymer matrix resulting in more effective nanocapacitors formation; (ii) enhanced polarization centers in the graphene due to nitrogen/sulfur doping, leading to a higher dielectric constant; (iii) aligned codoped EEG sheets, increasing the effective surface area of the nanocapacitor structure, enhancing the dielectric permittivity of the nanocomposite, and decreasing the dielectric loss; and (iv) functional groups at the surface of EEG acting as conduction barriers and decreasing the possibility of direct contacts of graphene sheets, reducing the dielectric loss.

We present an electrochemical advanced oxidation process (eAOP) reactor employing expanded graphite, potassium iodide (KI), and electrical current, which demonstrates an exceptionally high rate of inactivation of E. coli (6log reduction in viable cells) at low current density 0.12 mA/cm^2), with low contact time (5 minutes) and low concentration of KI (10 ppm). Operando X-ray fluorescence mapping is used to show the distribution of iodine species in the reactor, and operando X-ray absorption spectroscopy in the anodic chamber reveals iodine species with higher effective oxidation state than periodate. Operando electrochemical measurements confirm the conditions in the anodic chambers are favourable for the creation of highly oxidized iodine products. The killing efficiency of this new eAOP reactor far exceeds that expected from either traditional iodine-based electrochemical water treatment or advanced oxidation systems alone, a phenomenon that may be associated with the production of highly oxidized iodine species reported here.

Redox flow batteries (RFBs) are a promising technology for grid scale stationary energy storage to complement renewable energy systems. These batteries have a relatively low energy density; however, they offer important advantages, including: long life-time; decoupled energy (arbitrarily large electrolyte volume) and power (electrode area); high round-trip efficiency; scalability and design flexibility; fast response; and low environmental impacts. These advantages make them superior to many energy storage technologies for stationary applications [1-4]. Among the various types of RFBs, vanadium RFBs (VRFBs) are an emerging technology for grid scale energy storage and the integration of renewable energy generation [5]. The membrane is a key component of a VRFB that separates the two half-cell electrolytes and prevents cross-mixing, while allowing the transport of ions during charge-discharge cycles [6]. The VRFB membrane should exhibit low vanadium ion permeability to minimize self-discharge, low cost, and long‐term chemical stability under normal operating conditions. A high proton conductivity and low vanadium ion crossover are known to improve the efficiency of VRFBs [6-7]. In this study, we present a novel composite Nafion based membrane that results in a significant increase in the VRFB performance. The composite membrane has been characterized for its chemical, structural, and thermal properties using appropriate analytical techniques. The battery performance was evaluated in a flow cell using a ‘zero-gap’ design with an electrode area of 5 cm2. The electrolytic solution, 1.6 M VOSO4 in 3 M H2SO4, was circulated through the cell. Thermally treated carbon papers were used as the cathode and anode electrodes. For charge-discharge experiments, a constant current density (10 to 80 mA cm−2) was applied with upper and lower voltage cut-offs of 1.65 and 0.8 V, respectively. The stability of the battery using the composite membrane was evaluated over 100 cycles. Figures 1 and 2 show the energy efficiency and capacity retention during 100 charge-discharge cycles. The results reveal that the energy efficiency was improved from 51% to 63% by using the composite membrane. In addition, the charge-discharge capacity and capacity retention improved by around 200% and 25%, respectively. This improvement can be attributed to a higher proton conductivity and lower vanadium permeability of the composite membrane. References: [1] M. Skyllas-Kazacos, L. Cao, M. Kazacos, N. Kausar, A. Mousa, Vanadium Electrolyte Studies for the Vanadium Redox Battery-A Review, ChemSusChem. 9 (2016) 1521–1543. [2] A.K. Singh, M. Pahlevaninezhad, N. Yasri, E. Roberts, Degradation of Carbon Electrodes in the All-Vanadium Redox Flow Battery, ChemSusChem. (2021). [3] K.E. Rodby, T.J. Carney, Y. Ashraf Gandomi, J.L. Barton, R.M. Darling, F.R. Brushett, Assessing the levelized cost of vanadium redox flow batteries with capacity fade and rebalancing, J. Power Sources. 460 (2020) 227958. [4] M. Pahlevaninezhad, P. Leung, M. Pahlevani, F. C. Walsh, C. Ponce de Leon, and E. P. L. Roberts, Experimental and Computational Studies of Disperse Blue-1 in Organic Non-Aqueous Redox Flow Batteries, J. Power Sources, Volume 500, 15 July 2021, 229942. [5] X.Z. Yuan, C. Song, A. Platt, N. Zhao, H. Wang, H. Li, K. Fatih, D. Jang, A review of all-vanadium redox flow battery durability: Degradation mechanisms and mitigation strategies, Int. J. Energy Res. (2019). https://doi.org/10.1002/er.4607. [6] X. Li, H. Zhang, Zh. Mai, H. Zhang, I. Vankelecom, Ion exchange membranes for vanadium redox flow battery (VRB) applications, Energy Environ. Sci., 2011, 4, 1147. [7] L. Yu, F. Lin, L. Xua, J. Xi, A recast Nafion/graphene oxide composite membrane for advanced vanadium redox flow batteries, RSC Adv., 2016, 6, 3756. Figure 1