The volumetric capacities and the lifetime of organic redox flow batteries (RFBs) are strongly dependent on the concentrations of the redox-active molecules in the electrolyte. Single-molecule redox targeting represents an efficient approach toward realizing viable organic RFBs with low to moderate electrolyte concentrations. For the first time, an all-organic Nernstian potential-driven redox targeting system is investigated that directly combines a single-electrode material from organic radical batteries (ORBs) with a single redox couple of an aqueous, organic RFB, which are based on the same redox moiety. Namely, poly(TEMPO-methacrylate) (PTMA) is utilized as the redox target ("solid booster") and N,N,N-2,2,6,6-heptamethylpiperidinyloxy-4ammonium chloride (TMATEMPO) is applied as the sole redox mediator to demonstrate the redox targeting mechanisms between the storage materials of both battery types. The formal potentials of both molecules are investigated, and the targeting mechanism is verified by cyclic voltammetry and state-of-charge measurements. Finally, battery cycling experiments demonstrate that 78−90% of the theoretical capacity of the ORB electrode material can be addressed when this material is present as the redox target in the electrolyte tank of an operating, aqueous organic RFB.

Trimethylammonium-2,2,6,6-tetramethylpiperidine-1-oxyl chlorid (TMA-TEMPO) has been intensively studied for the usage in aqueous organic redox flow batteries. A straightforward synthesis, a reliable electrochemistry, fast kinetics and high cyc¬ling stability are the...

The presented study reports the synthesis and the vibrational spectroscopic characterization of different matrix-embedded model photocatalysts. The goal of the study is to investigate the interaction of a polymer matrix with photosensitizing dyes and metal complexes for potential future photocatalytic applications. The synthesis focuses on a new rhodamine B derivate and a Pt(II) terpyridine complex, which both contain a polymerizable methacrylate moiety and an acid labile acylhydrazone group. The methacrylate moieties are afterward utilized to synthesize functional model hydrogels mainly consisting of poly(ethylene glycol) methacrylate units. The pH-dependent and temperature-dependent behavior of the hydrogels is investigated by means of Raman and IR spectroscopy assisted by density functional theory calculations and two-dimensional correlation spectroscopy. The spectroscopic results reveal that the Pt(II) terpyridine complex can be released from the polymer matrix by cleaving the C═N bond in an acid environment. The same behavior could not be observed in the case of the rhodamine B dye although it features a comparable C═N bond. The temperature-dependent study shows that the water evaporation has a significant influence neither on the molecular structure of the hydrogel nor on the model photocatalytic moieties.

A shorter and more facile synthetic route for a cross-linked polymer based on the Blatter radical with a higher gravimetric capacity is presented. The material is processed in electrode films and characterized via cyclic voltammetry and galvanostatic experiments. Several electrolyte mixtures are investigated to identify optimal conditions for the new material. The electrodes are utilized as a cathode material vs activated carbon in coin cells, where high currents of up to 60 C are applied, with a capacity retention of 24% compared to 1 C. In long-term experiments, the material reveals a promising stability with a capacity retention of 99% after 1000 cycles at 5 C. A comparison with a previously reported Blatter radical-based electrode material is done to investigate the influence of the molecular structure on the battery performance.

A new anthraquinone based anolyte material for redox flow batteries revealed an extraordinarily high stability at elevated electrolyte temperatures.