ZnO monodispersed microspheres exhibiting only a c(þ)-plane on the surface were successfully synthesized by a novel soft-chemical solvothermal method with ethylene glycol (EG) and hexamethylenetetramine. The concentration of EG plays a critical role in the formation of these spherical particles. The spherical particles are dense and have hierarchical structure, where small crystallites are radially aligned along the c-axis. The polarity was determined using convergent-beam electron diffraction, and we established that the whole surface of the microspheres is a c(þ)-plane.
A robust ceramic
solid electrolyte with high ionic conductivity
is a key component for all-solid-state batteries (ASSBs). In terms
of the demand for high-energy-density storage, researchers have been
tackling various challenges to use metal anodes, where a fundamental
understanding on the metal/solid electrolyte interface is of particular
importance. The Na+ superionic conductor, so-called NASICON,
has high potential for application to ASSBs with a Na anode due to
its high Na+ ion conductivity at room temperature, which
has, however, faced a daunting issue of the significantly large interfacial
resistance between Na and NASICON. In this work, we have successfully
reduced the interfacial resistance as low as 14 Ω cm2 at room temperature by a simple mechanical compression of a Na/NASICON
assembly. We also demonstrate a fundamental study of the Na/NASICON
interface in comparison with the Na/β′′-alumina
counterpart by means of the electrochemical impedance technique, which
elucidates a stark difference between the activation energies for
interfacial charge transfer: ∼0.6 eV for Na/NASICON and ∼0.3
eV for Na/β′′-alumina. This result suggests the
formation of a Na+-conductive interphase layer in pressing
Na metal on the NASICON surface at room temperature.
This study investigated the effect of UV light irradiation on a Pt working electrode during the anodic electrodeposition of ceria (CeO 2 ) thin films in an aqueous solution containing Ce 3+ . UV light irradiation on the Pt anode induced the formation of holes in the valence band of anodically preformed CeO 2 nuclei, which serve as photoabsorbers. The resultant holes oxidized Ce 3+ to CeO 2 at the CeO 2 /solution interface as well as at the bare Pt surface. That is, CeO 2 itself acted as a sensitive layer for photoelectrochemical deposition. Although the current efficiency was reduced by the UV irradiation, the deposition amount and crystal size of CeO 2 clearly increased as compared to the dark process. It was verified that the oxygen saturation of the electrolyte solution was also effective in enhancing the deposition. In this paper, the photoelectrochemical deposition mechanism of CeO 2 is discussed in detail, and the positive effects of photoirradiation on film quality are demonstrated.
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