A Self-Supported CuO/Cu Nanowire Electrode as Highly Efficient Sensor for COD Measurement

Abstract

A self-supported CuO/Cu nanowire electrode (CuO/CuNWE), which was prepared by annealing Cu nanowires to form a porous Cu nanowire electrode (CuNWE) and then anodizing the as-prepared CuNWE in alkaline medium to generate Cu(OH)₂ nanowires followed by calcination, was employed for chemical oxygen demand (COD) determination using cyclic voltammetry (CV). The structure and electrochemical behavior of the CuO/CuNWE were investigated by scanning electron microscopy, X-ray diffraction, and CV. The results indicated that the as-synthesized CuO/CuNWE, in which CuO nanowires with a length of several micrometers and a diameter of 100 to 300 nm could be found, was stable in alkaline medium and more electrocatalytically active for oxidizing a wide range of organic compounds in comparison with the CuNWE. Under optimized alkaline concentration and scan rate, the CuO/CuNWE exhibited a good performance for COD measurement, with a linear range of 5 to 1153 mg L^-1, a sensitivity of 2.46× 10^-2 mA /(mg L^-1), and a detection limit of about 2.3 mg L^-1. In addition, an excellent correlation was observed in COD values obtained by our method and the classic dichromate method (r = 0.9995, <i>p</i> < 0.01, n = 11). Finally, our method was successfully used to measure the COD values in real water samples, showing great potential for practical application in water pollution control.