Rapid and Reliable Electrochemical Measurement of Chemical Oxygen Demand Using SnO₂–Sb-Based Anodes

Abstract

Chemical oxygen demand (COD) indicates the relative content of organics in water. The electrochemical measurement of COD is a promising ecofriendly alternative method for rapidly, automatically, and highly accurately determining the content of organics in water. However, the key anodes must possess high catalytic efficiency and long-term stability, be easy to prepare, and be free of heavy metal leaching. Therefore, in this study, a SnO2–Sb-based porous anode was prepared using simple coating and calcination. Because of its porous, conductive, and robust Ti felt/Pt (TF/Pt) substrate, the anode (TF/Pt/SnO2–Sb) possessed stable current responses that were highly correlated (R 2 = 0.999) with COD measurements in the range of 20–6000 mg L–1. The detection limit was 3.03 mg L–1 (at a signal-to-noise ratio of 3), and the relative standard deviation was within 3.2% (n = 10), which is superior to those of the standard dichromate detection method. The further assembly of a flow-through system with the proposed anode exhibited a wider linear range of up to 8000 mg L–1 at a lower sample injection volume of 50 μL. These results suggest the application potential of the electrochemical method with the porous TF/Pt/SnO2–Sb anode as a reliable alternative for sustainable COD determination.