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Paterson, Alisa R.

Publications and source records attributed to Paterson, Alisa R..

5 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

A general synthesis of single atom catalysts with controllable atomic and mesoporous structures

The control of single metal atomic sites has been extensively studied in the field of single atom catalysts. By contrast, the precise control of the mesoporous structure in the matrix material, which directly correlates with mass diffusions and may play a dominant role in delivering industrially relevant reaction rates, has been overlooked. In this work, we report a general method for the synthesis of a single atom catalyst with control of the atomic structure of the single atomic site as well as the mesoporous structure of the carbon support for optimized catalytic performance. Various combinations of metal centres (Ni, Co, Mn, Zn, Cu, Sc and Fe) and mass diffusion channels in two dimensions and three dimensions were achieved. Using CO 2 reduction to CO as an example, our Ni single atom catalyst with three-dimensional diffusion channels delivered a practical current of 350 mA cm –2 while maintaining a 93% CO Faradaic efficiency, representing a sixfold improvement in turnover frequency compared to two-dimensional counterparts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Confined Interlayer Water Promotes Structural Stability for High-Rate Electrochemical Proton Intercalation in Tungsten Oxide Hydrates

There is widespread interest in determining the structural features of redox-active electrochemical energy storage materials that enable simultaneous high power and high energy density. Here, we present the discovery that confined interlayer water in crystalline tungsten oxide hydrates, WO 3 · n H 2 O, enables highly reversible proton intercalation at subsecond time scales. By comparing the structural transformation kinetics and confined water dynamics of the hydrates with anhydrous WO 3 , we determine that the rapid electrochemical proton intercalation is due to the ability of the confined water layers to isolate structural transformations to two dimensions while stabilizing the structure along the third dimension. As a result, these water layers provide both structural flexibility and stability to accommodate intercalation-driven bonding changes. Furthermore, this provides an alternative explanation for the fast energy storage kinetics of materials that incorporate structural water and provides a new strategy for enabling high power and high energy density with redox-active layered materials containing confined fluids.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Polarization Mechanisms in P(VDF-TrFE) Ferroelectric Thin Films

Ferroelectric polymers have amassed tremendous attention due to several attractive properties including high breakdown strength, low dielectric loss, relatively fast charge/discharge rates and greater flexibility than their ceramic counterparts. In order to achieve enhanced energy efficiency in high-energy storage capacitor applications, it is desirable to obtain slim polarization hysteresis loops for ferroelectric polymer films. Here, it has been demonstrated that promotion of large crystallites and γ phase content through thermal annealing provides a cost-effective way to obtain a quasi-linear polarization response in a PVDF co-polymer thin film. The polarization mechanisms underlying a thin hysteresis loop in the thermally annealed film are elucidated using direct experimental insights from in situ synchrotron diffraction with two-dimensional detection. It has been demonstrated that the susceptibility for electric-field-induced structural changes is higher in the defective ferroelectric γ phase than the polar phase β, due to a higher flexibility for accommodation of gauche bond along the carbon chain. In addition, the polymer chains in the γ phase also exhibit a range of different responses depending on their orientations with respect to the electric field. These conclusions are broadly significant as they provide a fundamental basis for rational design of phase assemblages to obtain tailor-made properties in ferroelectric polymer films.

36 MATERIALS SCIENCE↗