Holmium Metal Nanoparticle PbO2 Anode Formed by Electrodeposition for Efficient Removal of Insecticide Acetamiprid and Improved Oxygen Evolution Reaction

This work examines the possibility of using a PbO₂-based electrode doped with the rare-earth metal holmium in the field of oxygen evolution and the development of an efficient method for the degradation of acetamiprid. Acetamiprid is a widely used insecticide and, as such, it very often reaches waterways, where it can cause many problems for wildlife and the environment. X-ray powder diffraction analysis, Raman spectroscopy, and energy-dispersive X-ray spectroscopy results confirmed the structure of Ti/SnO₂-Sb₂O₃/Ho-PbO₂, while the morphology of its surface was investigated by scanning electron microscopy with energy-dispersive X-ray spectroscopy. Ti/SnO₂-Sb₂O₃/Ho-PbO₂ showed good OER activity in alkaline media with a Tafel slope of 138 mV dec^-1. The Ti/SnO₂-Sb₂O₃/Ho-PbO₂ electrode shows very good efficiency in removing acetamiprid. By optimizing the degradation procedure, the following operating conditions were obtained: a current density of 20 mA cm^-2, a pH value of the supporting electrolyte (sodium sulfate) of 2, and a concentration of the supporting electrolyte of 0.035 M. After optimization, the maximum efficiency of removing acetamiprid (10 mg L^-1, 4.5 × 10^-5 mol) from water was achieved, 96.8%, after only 90 min of treatment, which represents an efficiency of 1.125 mol cm^-2 of the electrode. Additionally, it was shown that the degradation efficiency is strictly related to the concentration of the treated substance.