Eric J. Dufek

Electrochemical production of syngas from CO2 captured in switchable polarity solvents

An operational advantage that enables the deployment of technologies for the valorization of CO2 can be achieved through the integration of the capture and conversion technologies. In that perspective, switchable polarity solvents (SPS) were assessed as re-usable capture-electrolyte media for the electrochemical production of syngas at low temperatures and pressures. A polymer electrolyte membrane cell was used to liberate captured CO2 gas in proximity to the cathode without the addition of CO2 gas. Due to the proximate location of release, the produced syngas had minimal CO2 dilution with H2 : CO ratios between 2 to 4. For the first time captured CO2 has been reduced to CO with conversions and yields over 70% and at current densities over 100 mA cm−2.

A new detection mechanism involving keto–enol tautomerization: selective fluorescence detection of Al(III) by dehydration of secondary alcohols in mixed DMSO/aqueous media

A new mechanism for the fluorescence detection of metal cations in solution is introduced involving a unique keto–enol tautomerization. Reduction of 1,8-anthraquinone-18-crown-5 yields the doubly reduced secondary alcohol, 2. Compound 2 acts as a chemodosimeter for Al(III) ions producing a strong blue emission due to the formation of the anthracene fluorophore, 3, via dehydration of the internal secondary alcohol in DMSO/aqueous solution. The enol form is not the most thermodynamically stable form under these conditions however and slowly converts to the keto form 4. Reduction of 1 with Fe/AcOH or the reaction of 2 with HCl directly yields compound 4, the keto tautomer of 3, which also produces the same blue emission in more polar solvents. Competition studies reveal that compound 2 produces a blue emission exclusively in the presence of the strong Lewis acidic Al(III) ion and at relatively low pH.

Sampling dynamics for pressurized electrochemical cells

A model describing the gas distribution within a constant pressure electrolysis system and how the distribution impacts electrochemical efficiencies is presented. The primary system of interest is the generation of syngas (CO and H2) associated with the co-electrolysis of H2O and CO2. The model developed for this system takes into account the primary process variables of operation including total system pressure, applied current, and the in-flow of reactant gases. From these, and the chemical equilibria within the system, the impact on electrochemically generated gases is presented. Comparison of predicted and measured faradaic efficiency of an electrodes processes reveals significant disagreement under certain conditions. Methods to minimize and account for the discrepancy are presented with the goal of being able to discern, in a real-time manner, degradation of electrode performance. Comparison of the model to experimental data shows a strong correlation between the two with slight variation in experimental data, which is attributed to reversible system dynamics such as wetting of the gas diffusion electrode used as the cell cathode.

2.20 Batteries

In order to meet the growing global energy demand, while preserving environment, it is important to develop comprehensive electrochemical energy storage (EES) systems for a sustainable future to reduce the dependence on nonrenewable energy sources and greenhouse gas emissions. Batteries are among the major EES systems, which have the promise to meet the sustainable energy needs. Among all practical battery technologies, the rechargeable lithium-ion battery is the leading technology. This chapter covers fundamental characteristics of batteries, current challenges of battery materials and related cell chemistries, and brief overviews of state-of-the-art battery materials.

Section IV.D.3 for DOE 2013 Annual Report: Novel Phosphazene-based Compounds to Enhance Safety and Stability of Cell Chemistries for High Voltage Applications (INL)

Electrolytes play a central role in performance and aging in most electrochemical systems. As automotive and grid applications place a higher reliance on electrochemical stored energy, it becomes more urgent to have electrolyte components that enable optimal battery performance while promoting battery safety and longevity. Safety remains a foremost concern for widespread utilization of Li-ion technology in electric-drive vehicles, especially as the focus turns to higher voltage systems (5V). This work capitalizes on the long established INL expertise regarding phosphazene chemistry, aimed at battery-viable compounds for electrolytes and electrodes that are highly tolerant to abusive conditions. This report showcases our 2013 work for the DOE applied battery research (ABR) program, wherein testing results are summarized for INL electrolytes and alternative anode materials.