Synthesis of octahedral-like ZnO/ZnFe2O4 heterojunction photocatalysts with superior photocatalytic activity

Octahedral-like ZnO/ZnFe2O4 heterojunction photocatalysts were synthesized via a solvothermal method followed by thermal treatment. Appropriate amount of CH3COONa was introduced into the synthesis process to supply a moderate alkaline condition and slowly accelerate hydrolysis of ZnSO4 and FeCl3. The structure, morphology and photoelectric properties of samples were analyzed, and the results indicated that the as-synthesized samples with octahedral-like morphology and superior light absorption characteristics were assembled of ZnO and ZnFe2O4 crystallites as well as dispersed in various orientations. Compared with ZnO and ZnFe2O4, the ZnO/ZnFe2O4 photocatalysts exhibited enhanced photocatalytic activity in degradation of methylene blue. Especially, the optimal photocatalyst (ZF3) showed the highest catalytic activity, achieving 91.2% and 82.7% degradation efficiency after 120 min of UV-vis (350 <= lambda <= 780 nm) and 140 min of visible-light (lambda >= 420 nm) irradiation, respectively. The degradation process agreed well with pseudo-first-order kinetics. The improved photocatalytic activity was attributed to the synergetic effect of low bandgap energy, mesoporous structure and efficient charge separation, which enhanced the visible-light utilization and adsorption of pollutants.