Influence of iridium content on electrochemical performance of tantalum interlayer-coated titanium anodes

• The influence of iridium content on the electrochemical properties of titanium-based Ta/IrO 2 -Ta 2 O 5 coated anodes used in electrolytic copper foil was studied. • As the iridium content increased, more highly catalytically active iridium oxide crystals formed on the coating surface, while tantalum pentoxide existed in an amorphous form. • The distribution of iridium and tantalum elements highly coincides, and the sandblasting process of the titanium substrate enhances the adhesion between the coating and the substrate. • The surface of the coating with iridium content of 30 g/m 2 produced more cracks, which increased the contact area with the interface of the solution, and led to the enhancement of its electrocatalytic activity. Electrolytic copper foil is an important material for the manufacture of copper-clad laminates (CCL), printed circuit boards (PCB), and lithium-ion batteries. Coated titanium anodes of IrO 2 -Ta 2 O 5 for electrolytic copper foils with different iridium contents were prepared by the conventional thermal decomposition method. The crystal structure, surface and cross-section elements, surface and cross-section morphology of the coated titanium anodes with different iridium contents were analyzed using XRD, EDS and SEM. The electrochemical performance of the anodes was analyzed by testing the polarization curves, cyclic voltammetry and electrochemical impedance of the coated titanium anodes with different iridium contents. The results indicated that the crystal structures of the coatings with iridium contents of 21, 25, 28, and 30 g/m² were identical. As the iridium content increases, more elemental iridium is oxidized, forming iridium oxide crystals, causing more IrO 2 crystals to precipitate. Higher iridium content leads to increased formation of oxides, which, during the sintering process, results in a larger disparity in the coefficient of thermal expansion between the coating and the titanium substrate, thereby generating more cracks. Following cyclic voltammetry and electrochemical impedance spectroscopy tests, the charge from cyclic voltammetry and the charge transfer resistance for the anode with an iridium content of 25 g/m² were respectively 0.71 and 2.44 times those of the anode with an iridium content of 30 g/m². This suggests that a higher concentration of iridium oxide crystals and cracks is beneficial to the electrochemical performance of the coating.