Comparison of two different nickel oxide films for electrochemical reduction of imidacloprid

A nickel oxide (NiO) thin film was successfully prepared on Ni foil via a sol–gel method and a reduced state nickel oxide (r-NiO) thin film was obtained by etching NiO with hydrazine hydrate solution. Structure characterization through X-ray diffraction and scanning electron microscopy revealed the growth of nanostructure films on the surface of nickel foil. Cyclic voltammetry, linear sweep voltammetry and electrochemical impedance spectroscopy were used to assess the performance of the two films. Electroreduction of alkaline imidacloprid solution under potentiostatic conditions was carried out in a three-electrode system. The removal efficiencies of 80.2% (r-NiO) and 66.3% (NiO), and the current efficiencies of 67.3% (r-NiO) and 58.9% (NiO) were much higher than 41.7% (removal efficiency) and 0.003% (current efficiency) on the bare Ni electrode. This study prepared two novel thin films with composites of NiO or r-NiO, and thus provided feasible and efficient electrochemical degradation of imidacloprid. The degradation products were characterized and the possible degradation pathways were proposed.