Preparation of Ti/RuO2-IrO2 electrodes and their application in broad-spectrum electrochemical detection of COD

An electrode with RuO2 and IrO2 co-deposited on a Ti surface (Ti/RuO2-IrO2), notable for its high catalytic activity and stability, was developed for the rapid and environmentally friendly electrochemical determination of chemical oxygen demand (COD). This study thoroughly examined factors influencing electrode preparation, COD detection mechanisms, and the factors affecting COD detection, as well as broad-spectrum analysis. Under optimal conditions, which include a deposition time of 53.5 min, a current density of 5.5 mA/cm2, and 2.35 mmol of RuCl3, the electrode achieved a linear correlation coefficient of 0.99 for COD detection. The co-doping of RuO2 and IrO2 significantly enhanced the electrode's specific surface area and charge transfer rate, thereby improving the oxidation of organic compounds. The detection limit for COD was established at 1.8 mg/L, with a range of 0-250 mg/L, using an oxidation potential of 0.90 V and an electrolysis time of 150 s at an initial electrolyte pH of 6 with 0.03 mol/L NaNO3. The electrode effectively oxidized organic compounds across this range and demonstrated tolerance to chloride concentrations up to 800 mg/L. Electrode stability was confirmed through 30 repetitive cycles with no significant performance degradation. The detection results for simulated water samples were in strong agreement with the results obtained from the dichromate colorimetric method, with a linear equation of y = 0.01x+1.11, with an R2 of 0.99. The detection outcomes for six different sources of real water samples indicated consistent correlation between the electrochemical COD detection method using the Ti/RuO2-IrO2 electrode and the dichromate colorimetric method. This research showed the Ti/RuO2-IrO2 electrode has certain potential as COD detection element, leveraging its high charge transfer rate and extensive active area.