Electrochemical sensing chemical oxygen demand based on the catalytic activity of cobalt oxide film

• Published in: Analytica chimica acta Vol. 736; pp. 55 - 61
• Main Authors: Wang, Jinqi, Wu, Can, Wu, Kangbing, Cheng, Qin, Zhou, Yikai
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 29.07.2012; Elsevier
• Subjects: Acetates; Analysis methods; Analytical chemistry; Applied sciences; Biological Oxygen Demand Analysis; Carbon - chemistry; Catalysis; Chemical oxygen demand (COD); Chemistry; Cobalt - chemistry; Cobalt oxide; Cobalt oxides; Crack opening displacement; Detection; Electrochemical methods; Electrochemical sensor; Electrochemical Techniques - instrumentation; Electrodeposition; Electrodes; Exact sciences and technology; General, instrumentation; Glass - chemistry; Lakes - chemistry; Limit of Detection; Mathematical analysis; Microscopy, Atomic Force; Natural water pollution; Oxidation-Reduction; Oxides - chemistry; Oxygen demand; Pollution; Surface chemistry; Surface Properties; Three dimensional; Water Pollutants - analysis; Water pollution; Water treatment and pollution; Cobalt oxide; Chemical oxygen demand (COD); Electrodeposition; Water pollution; Electrochemical sensor; Atomic force microscopy; Cobalt Oxides; Electrochemical method; In situ; Fresh water; Roughness; Time; Cobalt; Electrocatalysis; Accuracy; Signal; Three dimensional structure; Chemical oxygen demand; Detection limit; pH; Oxidation; Surface activity; Surface potential; Catalytic reaction; Sample; Carbon electrode; Acetate; Concentration; Chemical sensor; Electrochemical detector; Sensitivity; Valence; Morphology; Application
• ISSN: 0003-2670; 1873-4324
• DOI: 10.1016/j.aca.2012.05.046

[Display omitted] ► A novel electrochemical sensor was developed for COD using cobalt oxide film. ► It exhibited high sensitivity, rapid response, good simplicity and practicability. ► It was used in numerous water samples, and accuracy was tested by standard method. Cobalt oxide sensing film was in situ prepared on glassy carbon electrode surface via constant potential oxidation. Controlling at 0.8V in NaOH solution, the high-valence cobalt catalytically oxidized the reduced compounds, decreasing its surface amount and current signal. The current decline was used as the response signal of chemical oxygen demand (COD) because COD represents the summation of reduced compounds in water. The surface morphology and electrocatalytic activity of cobalt oxide were readily tuned by variation of deposition potential, time, medium and Co2+ concentration. As confirmed from the atomic force microscopy measurements, the cobalt oxide film, that prepared at 1.3V for 40s in pH 4.6 acetate buffer containing 10mM Co(NO3)2, possesses large surface roughness and numerous three-dimensional structures. Electrochemical tests indicated that the prepared cobalt oxide exhibited high electrocatalytic activity to the reduced compounds, accompanied with strong COD signal enhancement. As a result, a novel electrochemical sensor with high sensitivity, rapid response and operational simplicity was developed for COD. The detection limit was as low as 1.1mgL−1. The analytical application was studied using a large number of lake water samples, and the accuracy was tested by standard method.