Person:

Gao, Jinxu

Aqueous redox flow batteries (ARFBs) constitute a promising technology for grid-scale electricity storage, but it is challenging to implement cell voltages exceeding the 1.23 V thermodynamic water splitting window with high Coulombic efficiency and long lifetime. pH decoupling – the creation of a pH difference between the negolyte and posolyte – can broaden the operating voltage window and improve long-term operational stability. This penalizes the efficiency, however, due to acid-base crossover induced by the pH gradient. As the voltage of the water splitting window varies linearly with pH whereas crossover fluxes vary exponentially, we employed mildly acidic and mildly basic electrolytes to develop a cell with high round-trip energy efficiency at an open-circuit voltage > 1.7 V. Moreover, we implemented an in situ acid-base regeneration system to periodically restore the negolyte and posolyte pH to their initial values. The combined system exhibits a capacity fade rate of less than 0.07% per day, a roundtrip energy efficiency of over 85%, and a Coulombic efficiency of approximately 99%. This work demonstrates principles for addressing critical issues such as lifespan, rate capability, long-term practicability, and energy efficiency in pH-decoupling ARFBs, providing guidance for the design of the next generation of high-voltage ARFBs.

We report the synthesis of an electronically-tuned minimally interfering photo-affinity label (MI-PAL), a compact five-carbon tag functionalized with an alkyl diazirine and alkyne handle. MI-PAL is compatible with protein photo-conjugation, click chemistry and mass spectrometry and readily installed to complex molecules for biological target identification.

Designing electrolytes based on mixture of different organic redox active molecules brings the opportunity of enhancing the volumetric energy density of flow batteries and removes the requirement of high solubility for individual organic species in the mixture. In the present work, we conduct computational and experimental analysis to investigate the electrochemical performance of mixed redox-active organic molecules. A zero-dimensional transient model is employed to investigate the changes in the half-cell potential and the concentrations and partial currents of individual redox reactions in a mixture of organic molecules over time. The model demonstrates the effects of individual properties of species such as kinetic rate constants, mass transfer coefficients, concentration ratios and standard redox potentials and reports the effect of energy-losing homogenous chemical redox reaction on the voltage efficiency and concentration ratios of the mixed species. Pairs of anthraquinone negolyte species were selected for an experimental case study. A mixture of 2,6-N-TSAQ and 2,6-DHAQ showed 40% increase in the volumetric energy density compared to the performance of 2,6-DHAQ alone. Based on the results of the experimental and computational analysis, we propose guidelines for the design of suitable mixed redox-active organic species.