The electrochemical/electrocatalytic behaviour of the Pd(IV)/Pd(II) redox pair as well as the reduction behaviour of palladous (Pd(II)) oxide on the palladium oxide (PdOx/Ti) electrode fabricated by thermal decomposition (denoted hereafter as type I electrode) and the type I electrode after cathodic polarization at 0 V (vs the) for 30 min (denoted hereafter as type II electrode) are studied by cyclic voltammetry (cv) and linear sweep voltammetry (Isv). The oxygen evolution reaction (OER) is more favourable on the type II rather than type I electrodes due to its higher hydration degree. There are a likely three Pd(IV) oxycations formed on the type I electrode, which are revealed by a combination of changing electrolyte’s pH values and adding ethanol in the solutions. The peak potential of palladous oxide reduction shifts to a less positive value with decreasing its hydration degree.