Spatial Separation of Electrons and Holes among ZnO Polar {0001} and {10(1)over-bar0} Facets for Enhanced Photocatalytic Performance

Spatial separation of electrons and holes is critical for improving their photocatalytic performance, which is ascribed to the suppressed photoinduced carriers' recombination among facets. In this work, the ZnO-Au-MnOx heterogeneous nanostructure photocatalyst was prepared by photodepositing Au and MnOx on the ZnO polar {0001} and {10 (1) over bar0} crystal facets, respectively. The photocatalytic performance of ZnO-Au-MnOx was higher than ZnO and ZnO-Au for the degradation of rhodamine B dye under UV light irradiation. Due to the potential difference between different crystal planes of zinc oxide, electrons and holes will migrate to different crystal planes of zinc oxide. This will lead to the deposition of Au and MnOx on different crystal facets of zinc oxide. The efficient photoinduced carrier separation of ZnO-Au-MnOx resulted in the high photocatalytic activity, which is well supported by photoelectrochemical and photoluminescence analyses. The intermediated species formed during the reaction were investigated by high performance liquid chromatography. The reaction mechanism was investigated by radical trapping experiments and electron spin resonance analysis. The special structure of selective deposition of redox cocatalysts on the different facets should be promising and intriguing for designing highly efficient photocatalysts.