Fig. 5.

Photocatalytic performance of MO dye under the illumination of UV light; (a) ZnO, (b) Cu/ZnO, (c) Ni/ZnO, and (d) Cu/Ni/ZnO (Experimental condition: dose of photocatalyst: 0.060–0.210 g, pH: 8.7, initial MO dye conc.: 10 mg L⁻¹).