This research found a cheap and efficient catalyst for electrooxidation of formaldehyde (HCHO). A CuO nano-crystalline modified glassy carbon electrode (GCE) was fabricated and had an excellent electrocatalytic activity towards the oxidation of HCHO. Both the effect of potential scan rate and the effect of HCHO concentration on the electrocatalytic oxidation performance of the electrode were investigated. The amperometric current response of the electrode was proportional to HCHO concentration in the range of 1.0 µmol•L -1 -10.0 mmol•L -1 with a detection limit (s/n＝3) of 0.25 µmol•L -1 . The electrode was stable, showing the CuO nano-crystlline is promising for applications in fuel cells and electrochemical sensors.

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As an alternative selection of electrocatalytic surface modifier, the electrochemically generated copper oxides is reinvestigated by using cyclic voltammetry (CV), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Interesting phenomena have been found, which indicate that the electrodeposition from the Cu 2＋ solution under cyclic voltammetric conditions can generate a transparent Cu(OH) 2 crystalline on the surface of glassy carbon electrodes, and this crystalline can be further transferred to a novel cubic opaque CuO crystalline of about 300 nm in size by second step of cyclic voltammetry in pH 12 NaOH solution. The final electrode (denoted as nano-CuO/GCE) can catalyze the oxidation (as well as the reduction) of H 2 O 2 in basic solutions. It shows pH dependent three-part catalytic mechanism in the range from pH 7 to pH 14. In 0.10 mol/L NaOH solution, the amperometric response at 0.15 V (vs. SCE) can give a current sensitivity as high as 139 mA/(mol•L -1 ) in the rage of 5.0×10 -7 -6.0×10 -4 mol/L with a lower detection limit (s/n＝3) of 2.5×10 -8 mol/L, and a current sensitivity of 78.4 mA/(mol•L -1 ) in the rage of 6.0×10 -4 -2.0×10 -3 mol/L. This electrode also has excellent reproducibility and stability. The mechanisms for the two steps of preparation and the catalytic reactions are proposed. The nano-CuO crystalline modified electrode may have more applications in the field of electrochemical sensing.