Abstract
Forces acting on a functional nanomaterial during operation can cause plastic deformation and extinguish desirable catalytic activities. Here, we show that sacrificial materials, introduced into the catalytic composite device, can absorb some of the imposed stress and protect the structural integrity and hence the activity of the functional component. Specifically, we use molecular dynamics to simulate uniaxial stress on a ceria (CeO2) nanocube, an important functional material with respect to oxidative catalysis, such as the conversion of CO to CO2. We predict that the nanocube, protected by a "soft" BaO or "hard" MgO sacrificial barrier, is able to withstand 40.1 or 26.5 GPa, respectively, before plastic deformation destroys the structure irreversibly; the sacrificial materials, BaO and MgO, capture 71 and 54% of the stress, respectively. In comparison, the unprotected nanoceria catalyst deforms plastically at only 2.5 GPa. Furthermore, modeling reveals the deformation mechanisms and the importance of microstructural features, insights that are difficult to measure experimentally.
Highlights
IntroductionThe properties of a functional material can be tuned by changing its size and shape (metamaterial sculpting) as an alternative to elemental control.[1]
The properties of a functional material can be tuned by changing its size and shape as an alternative to elemental control.[1]
We explore the deformation within the nanoceria test material and deformation suffered by the anvils, as well as the effect this may have on the catalytic activity
Summary
The properties of a functional material can be tuned by changing its size and shape (metamaterial sculpting) as an alternative to elemental control.[1]. Small forces can translate to considerable pressures when contact areas are reduced to the nanoscale. When the same force acts upon a contact area that is reduced from 1 cm[2] to 10 nm[2], the pressure increases by 13 orders of magnitude. Plastic deformation of a nanomaterial will irreversibly extinguish any desirable properties; it is vital to understand the mechanical properties of functional nanomaterials. Huang et al showed that the intercalation of Li into SnO2 nanowires introduced considerable localized stress. This resulted in plastic deformation and pulverization of the material; such major mechanical effects plague the performance and lifetime of high-capacity anodes in lithium-ion batteries.[3]
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