Long-Term Stability of Ferri-/Ferrocyanide as an Electroactive Component for Redox Flow Battery Applications: On the Origin of Apparent Capacity Fade

We assess the suitability of potassium ferri-/ferrocyanide as an electroactive species for long-term utilization in aqueous organic redox flow batteries. A series of electrochemical and chemical characterization experiments was performed to distinguish between structural decomposition and apparent capacity fade of ferri-/ferrocyanide solutions used in the capacity-limiting side of a flow battery. Our results indicate that, in contrast with previous reports, no structural decomposition of ferri-/ferrocyanide occurs at tested pH values as high as 14 in the dark or in diffuse indoor light. Instead, an apparent capacity fade takes place due to a chemical reduction of ferricyanide to ferrocyanide, via chemical oxygen evolution reaction. We find that this parasitic process can be further exacerbated by carbon electrodes, with apparent capacity fade rates at pH 14 increasing with an increased ratio of carbon electrode surface area to ferricyanide in solution. Based on these results, we report a set of operating conditions that enables the long-duration cycling of alkaline ferri-/ferrocyanide electrolytes and demonstrate how apparent capacity fade rates can be engineered by the initial system setup. If protected from direct exposure to light, the structural stability of ferri-/ferrocyanide anions allows for their practical deployment as electroactive species in long duration energy storage applications. © 2023 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited

Ion Transport Through Polymers: New Insights into the Design of Polymer films as Ion Transporting Membranes for Renewable Energy Applications

Lecture delivered on 28 September 2012 at Haverford College, KINSC, Hilles 109 by Sergio Granados-Focil, Assistant Professor of Chemistry at Clark University

Ring Opening Metathesis Polymerization of Triazole-Bearing Cyclobutenes: Diblock Copolymer Synthesis and Evaluation of the Effect of Side Group Size On Polymerization Kinetics

© 2017 Wiley Periodicals, Inc. Cyclobutenes containing pendant groups of varying sizes were polymerized via ring opening metathesis polymerization using Grubbs catalyst 2nd generation (G2). The rate of polymerization depended on the size of the pendant groups attached to the cyclobutene rings, with longer side-chains producing slower polymerization rates and narrower molecular weight distributions. The polymerization of these new molecules proceeded with first order kinetics, consistent with a living polymerization. Chain extension experiments produced cyclobutene-based diblock copolymers with polydispersity indices below 1.33. The synthetic methods in this report will allow the use of G2 to access new complex polymeric architectures with a higher density of pendant groups than those derived from norbornene analogs and cyclooctene moieties. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 1929–1939

Thermo-Optically Responsive Phase Change Materials for Passive Temperature Regulation

© 2020 International Solar Energy Society. Many phase change materials (PCMs) experience a change in transparency when undergoing a phase transition. These thermo-optically responsive materials can be used to generate passive temperature control systems for building enclosures. The integration of optical and thermal switches into smart temperature-controlling elements requires rationally designed PCMs featuring tunable optical and thermal properties. Two polymers, poly (Octadecyl methacrylate) (PSMA) and poly(2-(2-(octadecyloxy) ethoxy) ethyl methacrylate) (PE2SMA) were synthesized and evaluated for their potential use in passive thermal energy storage systems. UV–Visible Spectroscopy, Near Infra-Red Spectroscopy, and Differential Scanning Calorimetry were used to evaluate the effect that changes in the polymer chemical structure had on the optical and thermal properties of the resulting materials. Insertion of a 6-atom flexible spacer (diethylene glycol) between the pendant crystalline motif and the polymer backbone of PSMA resulted in increases of latent heat storage capacity from 62 J/g to 94 J/g and thermal conductivity from 0.218 W/mK to 0.318 W/mK. Notably, insertion of a flexible spacer also resulted in a melting transition temperature increase from 37.7 °C for PSMA to 48 °C for PE2SMA. The visible transmittance of the polymers increased from 0% to 90% upon transition from crystalline to amorphous state. This study presents a synthetic strategy to control thermal and optical properties of polymeric PCMs materials. The material properties and structure-property relationships derived from this study will enable the refinement of the models used to predict the performance of passive temperature-regulating systems. More accurate models will guide the development of the thermo-responsive polymeric materials required for better perfoming temperature-regulating building enclosures