AgI Microplate Monocrystals with Polar {0001} Facets: Spontaneous Photocarrier Separation and Enhanced Photocatalytic Activity.

Elucidating the facet-dependent photocatalytic activity of semiconductor photocatalysts is important in improving the overall efficiency of photocatalysis. Furthermore, combining facet control with selective deposition of oxidation and/or reduction cocatalysts on specific faces of semiconductor photocatalysts is potentially an effective strategy to synergistically optimize the functionality of photocatalysts. In the present study, high-purity wurtzite-type β-AgI platelet microcrystals with polar {0001} facets were prepared by a facile polyvinylpyrrolidone-assisted precipitation reaction. The polar-faceted AgI microplates were used as archetypes to demonstrate preferential diametric migration (i.e., effective separation) of photogenerated electrons and holes along the c axis. Such vectorial electron-hole separation stems from the asymmetric surface structures, which give rise to distinct photoexcited reaction behaviors on the ±(0001) polar facets of wurtzite-type semiconductors. Furthermore, on selective deposition of Ag and MnO x (1.5< x<2) cocatalysts on the reductive (0001) and oxidative (000 $\bar 1$) facets, respectively, photocatalytic activity of the AgI microplates in degrading organic pollutants was dramatically enhanced thanks to the broad light-absorption range, strong dye-adsorption ability, and effective spatial separation of photocarriers. [ABSTRACT FROM AUTHOR]