Inverse vulcanization combines elemental sulfur, a petroleum waste product, and organic monomers to synthesize high sulfur content polysulfides without the need for solvents. The low cost, synthetic ease, and diverse applications have led to the rapid growth of the field. Despite the novelty of inverse vulcanization, many alterations to the synthetic techniques have been introduced. A literature search revealed four primary methodologies that are being used under the umbrella of inverse vulcanization which were used to synthesize poly(S-DVB). Alterations to polymer structure, solubility, and hydrogen sulfide production were characterized. Despite seemingly minor synthetic changes, dramatic impacts on the polymer properties were observed. Analysis of the oxidized polymers by ATR-IR spectroscopy yielded insight into the sulfur rank for these polysulfides. The reported fundamental data provide a guide to determine and control the specific polymer makeup to tailor the material properties for a given application.
The
electrochemical production of rare earth metals (REMs) in ionic
liquids (ILs) has received much attention as a promising, sustainable
replacement to molten salt electrolysis. Water additives have been
suggested as a promoting strategy for the ionic liquid process; however,
the fundamental understanding of the interfacial processes required
to assess the overall viability for REM production is lacking. In
this regard, a full investigation of the impact of water on dysprosium
(Dy) electrodeposition in pyrrolidinium triflate (BMPyOTf) ionic liquid
was carried out. Water introduction was revealed to involve an interplay
of implications on the electrodeposition process, including coordination,
speciation, reduction pathways, interfacial dynamics, nucleation,
and metal stability and purity. Under highly dry conditions, the reduction
occurs at a very negative potential (−3.3 V) in a consecutive
pathway, resulting in negligible metal electrodeposition (low rate
and efficiency) at the electrode surface. Small water concentrations
(<500 ppm) lead to partitioning of the Dy complex between water
and IL-coordinated speciation, giving rise to an additional wave at
a more positive potential (−2.4 V). Probing the heterogeneous
Dy speciation by spectroscopic analyses enabled uncovering of the
reduction mechanism and evaluation of the mass transport properties.
In addition to lowering the reduction thermodynamics, water introduction
also improved the nucleation, deposition rate, and faradic efficiency.
Despite these benefits, stripping voltammetric analysis predicts substantial
chemical reactivity of the deposited Dy metal with water additives
and/or electrolyte components, under long timescales. Surface characterization
of the obtained product confirmed the instability of Dy metal as an
oxidized/fluorinated material and its limited purity (∼60%).
Moreover, high water introduction triggered a fast hydrogen evolution
reaction (HER), downgrading the robustness of system efficiency. The
overall impact of water additives seems to engender both promoting
and mitigating effects on electrochemical REM production in IL, requiring
a specific technoeconomic assessment and/or more innovative strategies
to be sought.
The reduction of rare earth elements (REE) such as Nd, Pr, and Dy to a stable metallic phase at low temperature is difficult due to the high reactivity of REEs. Non-aqueous electrolytes have been investigated due to their wider electrochemical window. While most work has focused on the cathodic reduction of REEs, little attention has been directed to the anode reaction. While not a focus of studies, the anticipated anode reaction is oxidation of the non-aqueous electrolyte. In this work, options for developing alternate anode reactions which do not degrade the electrolyte are being pursued as an alternate pathway of introducing REEs into non-aqueous electrolytes through an anodic reaction that could avoid degradation of the electrolyte. Investigations using electrochemical techniques such as cyclic voltammetry and chronoamperometry permit evaluation of various materials options.
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