Piezo-potential facilitated photocatalytic activation of persulfate over α-Fe2O3 and mechanism insight

Superoxide radical (O-2(center dot-)) is the main active species to generate sulfate radicals during the persulfate (PS) activation assisted by photocatalysis. As a widely-used photocatalyst, alpha-Fe(2)O(3 )usually exhibits negligible activity for O-2(center dot-) generation attributed to the low conduction band (CB) and photogenerated carrier mobility. In this work, we try to overcome the drawbacks by means of negative piezo-potential generated from strained ZnO nanorod. ZnO nanorod array is prepared by a hydrothermal method, and alpha-Fe2O3 is attached on it through a sol-gel process. The as-prepared showed obviously enhanced visible-light activity for PS activation under the impact of water flow, and the PS activation efficiency could reach 70% in 1 h. The activity is rarely decreased in 5 cycles and no Fe ions detected in the solution, indicating the nanocomposite possesses high stability. The enhanced activity is largely related to the additional negative piezo-potential generated in the top of ZnO nanorod. The resulted negative electric field could evaluate the CB of alpha-Fe2O3, thereby improving photogenerated charge reduction activity. Moreover, the field facilitates the opposite transports of photoelectrons and holes, due which the separation rate is enhanced. Consequently, the generation of O-2(center dot-) radicals which act as the dominant species in PS activation is promoted.

Automated summary

The generation of sulfate radicals during persulfate activation assisted by photocatalysis is mainly attributed to the superoxide radical (O-2(center dot-)). By utilizing negative piezo-potential generated from strained ZnO nanorod, the activity of alpha-Fe(2)O(3) for O-2(center dot-) generation is enhanced, leading to improved PS activation efficiency and stability of the nanocomposite. The additional negative electric field at the top of ZnO nanorod evaluates the conduction band of alpha-Fe(2)O(3), facilitating enhanced photogenerated charge reduction activity and separation rate, ultimately promoting the generation of O-2(center dot-) radicals in PS activation.