We present a colloidal route for the synthesis of ultrathin ZrS(2) (UT-ZrS(2)) nanodiscs that are ~1.6 nm thick and consist of approximately two unit cells of S-Zr-S. The lateral size of the discs can be tuned to 20, 35, or 60 nm while their thickness is kept constant. Under the appropriate conditions, these individual discs can self-assemble into face-to-face-stacked structures containing multiple discs. Because the S-Zr-S layers within individual discs are held together by weak van der Waals interactions, each UT-ZrS(2) disc provides spaces that can serve as host sites for intercalation. When we tested UT-ZrS(2) discs as anodic materials for Li(+) intercalation, they showed excellent nanoscale size effects, enhancing the discharge capacity by 230% and greatly improving the stability in comparison with bulk ZrS(2). The nanoscale size effect was especially prominent for their performance in fast charging/discharging cycles, where an 88% average recovery of reversible capacity was observed for UT-ZrS(2) discs with a lateral diameter of 20 nm. The nanoscale thickness and lateral size of UT-ZrS(2) discs are critical for fast and reliable intercalation cycling because those dimensions both increase the surface area and provide open edges that enhance the diffusion kinetics for guest molecules.
The activities of Au/AlPO 4 nanocomposites with the variation of metal phosphates were examined for oxygenreduction reactions, both in an alkaline and acidic environment. In an alkaline media, the activities of the Au/AlPO 4 nanocomposites on the oxygen-reduction were enhanced. The steeper reduction slope as well as larger reduction current density were observed in the potential range of approximately 0.8-1.0 V (vs reversible hydrogen electrode) with the newly appeared peak at ∼0.85 V. In an acidic media, the oxygen reduction on the Au/AlPO 4 nanocomposites presented both higher onset potential and steeper reduction slope than that on the Au catalyst. Such enhancements were attributed to the electronic interactions between Au and AlPO 4 , as confirmed by X-ray photoelectron spectroscopy.
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