Fabrication of CuO/CuiTiO₂ nanotube arrays modified electrode for detection of formaldehyde

A CuO/Cu/TiO2 nanotube arrays (TNAs) modified electrode was fabricated by electrochemical method. Cu first deposited on TNAs electrode by a galvanostatic pulse method and CuO was prepared by in-situ oxidation copper in alkaline solution through cyclic voltammetry (CV). The effect of the cycle number of cyclic voltammograms and different substrate on the sensing performance were investigated. It was found that the optimal cycle number of CV is 100. The optimal CuO/Cu/TNAs electrode presents high sensitivity (814 mu A mM(-1) cm(-2)) and wide linear range, with formaldehyde concentration from 65.0 mu M to 7.80 mM, a detection limit of 25.0 mu M (S/N = 3) and good repeatability, allowing prompt quantitative analysis of formaldehyde in alkaline solutions. Furthermore, compared to the glass carbon electrode (GCE) modified by a layer of CuO nanopaticles growing on the surface of Cu for the oxidation of formaldehyde, the CuO/Cu/TNAs electrode presents higher anodic oxidation current density and excellent cycling stability, showing that the CuO/Cu/TNAs electrode is more electro-active for oxidation of formaldehyde than the CuO/Cu/GCE. The prominent and stable electrocatalytic activity toward formaldehyde result from the synergistic effect between CuO/Cu and TNAs. In addition, the surface CuO nanoparticles on the CuO/Cu/TNAs electrode are more likely to form the highly active CuOOH species during oxidation process, which is the key to enhance the catalytic efficiency of CuO/Cu/TNAs electrodes. (C) 2020 Elsevier B.V. All rights reserved.