Characterization and electrochemical properties of stable Ni2+ and F- co-doped PbO2 coating on titanium substrate

Abstract

• A stable Ni 2+ and F - co-doped PbO 2 coating was fabricated by tsition method. • The electrochemical behavior of un-doped and doped PbO 2 coatings was evaluated before and after ALT. • Simultaneously doping of F - and Ni 2+ ions in PbO 2 coating leads to the best electrocatalytic activity. • The service life of Ni 2+ and F - co-doped Ti/SnO 2 -Sb 2 O 3 /PbO 2 electrode was several times as much as that of the un-doped electrode. In the present work, a novel Ni 2+ and F - co-doped PbO 2 coating featuring high stability toward electrochemical degradation was fabricated on titanium substrate by anodic electrodeposition method. The microstructure of the coatings was characterized using scanning electron microscopy (SEM), energy-dispersive X-Ray spectroscopy (EDS), and X-ray diffraction (XRD). The results showed that the addition of dopants into PbO 2 coating, encourages the formation of a compact coating without any cracks and pores on its surface. The stability of the Ti/SnO 2 -Sb 2 O 3 /PbO 2 electrode was measured using the accelerated life test (ALT) in chloride ion-containing solution with a large current density of 2.5 A.cm −2 . Before and after ALT, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were utilized to evaluate the electrochemical behavior of the electrodes. It was found that the service life of Ni 2+ and F - co-doped Ti/SnO 2 -Sb 2 O 3 /PbO 2 electrode was 120 h, such that was several times as much as that of the un-doped electrode. The results of EIS and CV measurements indicated that Ni 2+ and F - co-doped anode compared to F - doped and the un-doped anodes has the lowest charge transfer resistance and also the best electrocatalytic activity. These characteristics are due to the simultaneously doping of F - and Ni 2+ , which inhibited the penetration of chloride ions toward the titanium substrate and also delayed the formation of the non-conductive TiO 2 layer at the coating/substrate interface.