The potential range for metal oxide deposition on the PN-coated electrodes was determined similarly. The potential range for metal oxide deposition on the PN-coated electrodes was determined the same way. LSV was measured in the potential range between 0 and -1.0 V against SCE with a scan rate of 50 mV s -1 . Suitable potentials for the deposition of ZnO, Fe2O3, and ZnFe2O4 are -0.6 V, -0.7 V and -0.9 V respectively (see Figure ). and ZnFe2O4 in the synthesis precursor solution.