Energy Focus: Functionalized-carbon-supported Pt-Co alloy nanoparticle catalyst yields reduced-cost fuel cells
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ENERGY FOCUS
The normal practice during nanocrystal synthesis is to cover the surfaces with surfactants, the role of which is to impart colloidal stability to the nanocrystals and to enhance their optical properties by securing their surfaces from unwanted oxygen and moisture attack. One set of the surfaces of the TTQDs was intentionally covered with a different surfactant than the others. This surfacespecific surfactant coating had crucial implications when TTQDs were allowed to interact during self-assembly. Surface facets with similar surfactants had enhanced affinity to come closer, enhancing self-assembly and leading to decagonal units. Importantly, it was found that during self-assembly, the decagons could flexibly share edges and transform into polygons of five to nine edges wherever necessary to fill gaps. “The present work is a fascinating discovery on quasicrystalline assemblies from anisotropic nanocrystals,” says Xingchen Ye, an assistant professor of chemistry at Indiana University Bloomington, and an expert in quasicrystalline self-assembly. “The observed tenfold rotational symmetry is distinct from the dodecagonal symmetry
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Functionalized-carbon-supported Pt-Co alloy nanoparticle catalyst yields reduced-cost fuel cells
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uel cells are electrochemical devices that convert chemical energy stored in fuels (e.g., hydrogen gas) into electricity. Their functionality relies on a rapid oxygen reduction reaction (ORR) for energy generation. Since ORR is a non-spontaneous process with a high reaction potential barrier, electrocatalysts containing noble metals (e.g., Pt) are typically used to reduce this barrier and improve the fuel cell energy efficiency. The scarcity and high cost of Pt is one of the reasons hindering broad adoption of fuel cells. A research team led by Di-Jia Liu, a senior chemist at Argonne National Laboratory, recently developed a novel ORR catalyst with record low Pt mass (0.035 mgPt/cm2) that outperformed
predicted by computer simulations of assemblies of hard tetrahedra, motivating further investigations on how details of shape and interaction anisotropy encoded at the single-nanocrystal level lead to mesoscopic ordering.” The demonstration of QCSLs from single-component building blocks enabled by the discovery of the “flexible polygon tiling rule” has opened a new realm in the field of quasicrystalline structures and will enrich the tool chest for chemical synthesis of superstructures. “We have demonstrated a fundamentally new type of quasicrystal. The decagons form quasicrystalline superlattices by making their edges flexible, utilizing our flexible polygon tiling rule,” Chen says. “Our findings have implications for research in materials science, chemistry, mathematics, and even art and design.” Quantum dot superlattices are increasingly being explored for electronic and optoelectronic applications with claims of enhanced charge transport and optical properties due to increased order. The present study is anticipated to soon bring into view the exciting subfield of quantum d
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