Fractional factorial design applied to investigate properties of Ti/IrO2–Nb2O5 electrodes

Abstract The effects of the preparation variables on the electrochemical and morphological properties of Ti/IrO 2 –Nb 2 O 5 (60:40 mol%) electrodes prepared by the polymeric precursor method were investigated. In order to reduce the number of experiments, the study was carried out using a two-level fractional factorial design with resolution III. It was observed that the charge depends mainly on the temperature of calcination and on the composition of the precursor solution. An average decrease of 26.9 (mC cm −2 mg −1 ) was observed by changing the calcination temperature from 400 to 500°C. The average anodic charge decreased by 8.93 (mC cm −2 mg −1 ) when the molar ratio CA/EG (citric acid/ethylene glycol) was changed from 1:6 to 1:12. A similar behaviour was observed when the molar ratio between CA/PS (citric acid/precursor salt) was changed from 6:1 to 12:1, a decrease of 10.3 (mC cm −2 mg −1 ) being observed. The anodic charge decrease also occurred by increasing the time of calcination as well as controlling the heating rate. Once the temperature was the main variable affecting the anodic charge it was widely investigated in a range between 250 and 700°C. A maximum anodic charge was observed at 300°C while the electrode calcinated at 600°C showed the maximum value in the accelerated stability test (AST) for the oxygen evolving reaction in acid medium. The effects observed on the electrochemical properties were correlated with the morphological and microstructural changes occurring in the samples.