The role of ball milled h-BN in the enhanced photocatalytic activity: A study based on the model of ZnO

h-BN/ZnO composite photocatalysts were prepared by ball milling of ZnO with hexagonal BN (h-BN). The photocatalytic activity of ZnO for the degradation of cationic dyes could be significantly enhanced by coupling with ball milled h-BN and the stability of ZnO benefited from the presence of h-BN as well. However, for the degradation of anionic dyes, no apparent enhancement was observed. The optimal amount of h-BN and the ball milling time were found to be 1.0 wt.% and 20 min, respectively. Through various characterization techniques (XRD, UV-vis DRS, SEM, TEM, and terephthalic acid photoluminescence probing) and the compared photocatalytic degradation experiments, the observed photocatalytic behaviors could be attributed to the negatively charged h-BN created by the ball milling process. The role of the milled h-BN was discussed to serve as (1) holes-transfer promoter and (2) attractive or repulsive sites for the adsorption of the charged dyes via electrostatic forces. The study confirms that the ball milled h-BN could be used as a holes transfer promoter for ZnO. However, the finial photocatalytic performance of h-BN/ZnO is determined by the superposition of the two effects for a specific degradation process. This is the reason why the enhancement of ball milled h-BN is only effective for cationic dyes. (C) 2013 Elsevier B.V. All rights reserved.