Study On The Electrochemical Properties Of IrO₂-ZrO₂ Oxide Electrode

IrO2 were mainly applied to the titanium anodes of electrolysis industry due to their superior electrocatalytic activities and redox pseudo-capacitance characteristics inherently, which had achieved significant results. The structures of IrO2 electrode could be improved by adding some cheap metal elements, ZrO2 has strong ability to resist corrosion and excellent chemical stability, so it gets considerable concern in many fields such as fuel cells and structural ceramics, while in respect of the fields of titanium electrodes and the super capacitors, the research of adding Zr to coatings is little. In this paper, IrO2-ZrO2 binary oxide coatings deposited on Ti substrate were prepared by thermal decomposition and the effect preparation temperatures and Ir/Zr ratios had on the surface morphology, organization structure, surface composition, capacitive and catalytic performance of IrO2-ZrO2 binary oxide coatings were analyzed by XRD, SEM, EDX, XPS and CV, etc. After obtaining the the active sites located inside and outside of the coatings by a nonlinear equation, the band structure and density of rutile type IrxZri-xO2 solid solution were calculated by the first-principles calculation method. The result showed that:(1) Annealing temperature has significant influence on the structure and electrochemistry performance of 70% IrO2-30% ZrO/Ti electrode. The critical crystallization temperature of oxide coatings was between 340～360℃, moreover, with the increase of temperature, the crystallinity increased. With the rise of temperature, the specific capacitance of electrode increased first and then decreased, the electrode with annealing temperature at 360℃ exhibited biggest capacitance and excellent stability, even after 5000 cycles the capacitance did not decline. Under this condition, the oxide coatings on structure surface consisted of crystalline and amorphous structures, and it was also found that the existing states of Ir (Ⅲ), Ir (Ⅳ), as well as higher valence Ir atoms exist in the coatings;(2) ZrO2 could restrict the crystallization degree of IrO2, and with the increasing amount of zirconium, the crystallization degree of oxide coatings decreased. With the increasing amount of zirconium, the specific capacitance of electrode increased at the beginning and decreased later; When the content of ZrO2 was 50 mol%, the electrode showed typical "amorphous/crystalline" structure style, and it had the biggest specific capacitance value and most excellent catalytic activity;(3) Nonlinear equation could accurately be used to express the relationship between charge(q*) and scan rate(mV/s), and based on this, the active sites of coating surface could be calculated, which could better represent the information of active sites inside coatings compared with traditional linear extrapolation methods. The proton migration capacity had more influence on the capacitance than that of electronic conductivity. The effect of the CV scanning speed on proton migration was greater than that of electronic conductivity;(4) The electronic conductivity of IrO2-ZrO2 is worse with increasing Zr4+ content in the rutile type IrxZr1-xO2 solid solution with the replace of Ir with Zr, and the enery band gap increases from OeV to 3.25eV. In this case, the activities of the electrodes may rely on the proton diffusion.