First-principles calculations were employed to study the effects of the addition of ZrO 2 on the electrochemical activity and structure of Ir-Zr binary oxide. In the computation model employed, Zr atoms replaced Ir atoms in IrO 2 supercells, so as to form a rutile-type solid solution of Ir 1 -x Zr x O 2 (0 ≤ x ≤ 1). IrO 2 -ZrO 2 oxide coatings were prepared on Ti substrates by thermal decomposition. X-ray diffraction (XRD) analyses, cyclic voltammetry, and galvanostatic charge/discharge tests were performed to investigate the effects of the Zr content on the structure and capacitive performance of the synthesized Ti/IrO 2 -ZrO 2 electrodes. As the Zr content was increased, the density of state of Ir 1 -x Zr x O 2 moved to a higher energy level, and a forbidden band was formed, which reduced its electronic conductivity. The XRD analyses showed that ZrO 2 restrained the crystallization of IrO 2 . Thus, the extent of the amorphous phase increased with the increase in the ZrO 2 content, indicating that the proton conductivity of the binary oxide coating increased with the ZrO 2 content. When the ZrO 2 content was higher than 50 mol%, the IrO 2 -ZrO 2 coating exhibited a relatively narrow energy band gap (0.42eV) and a "amorphous/ crystalline" structure, as well as the highest charge capability, indicating that its electronic and protonic conductivities had reached an equilibrium. This was in accordance with the sudden variation in the length of the M-O bond and the change in the bulk modulus.

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