Electrochemical and morphological investigation on the effect of reduction temperature on the electrochemical behavior of a novel magnéli phase nanotubes on titanium

In this study the effect of hydrogen reduction temperature on the electrochemical performance of magneli phase titanium oxide nanotubes in oxygen evolution reaction (OER) was investigated. Anodizing of titanium led to the production of TiO₂ nanotubes. The anodized layer was annealed at 480 °C. The layer was finally exposed to a reducing atmosphere at temperature range of 700–900 °C. The surfaces of the samples were examined using scanning electron microscopy (SEM). The phases on the surface were characterized using X-ray diffraction (XRD) method. The electrochemical properties of the surface layer were studied using electrochemical impedance spectroscopy analysis (EIS) and cyclic voltammetry. The results showed that the nanotubes produced on the surface are completely destroyed when the heat treatment temperature is increased to 900 °C. Furthermore, the surface conductivity decreased as the titanium oxide in the rutile phase increased and the amount of Ti₄O₇ in the Magnéli phase decreased. During the reduction process, the maximum proportion of the Magnéli phase was reached at 700 °C. This sample also has the lowest charge transfer resistance value, which qualifies it for use as a novel electrocatalyst for oxygen evolution reactions.