Fig. 3
a Nyquist plots of the CuO/C-350oC, CuO/C-400 °C, CuO/C-450 °C and commercial CuO in 0.1 M KCl electrolyte containing 5 mM Fe(CN)63− /4− and an applied AC frequency range of 0.1–105 Hz at 0.2 V (vs. Ag/AgCl) with an amplitude of 5 mV; b Cyclic voltammograms of the CuO/C-400 °C electrodes in 0.1 M NaOH with/without 0.2 mM glucose at a scan rate of 100 mV·s− 1; c Amperometric i-t response of the CuO/C-350 °C, CuO/C-400 °C and CuO/C-450 °C electrodes in 0.1 M NaOH at 0.5 V (vs. SCE) with stirring, insert is the response current density of 1.0 mM glucose on the CuO/C-350 °C, CuO/C-400 °C and CuO/C-450 °C electrodes derived from Fig. 3c (MEAN ± SD, n = 3, *p < 0.05); d CV curves of CuO/C-400 °C in 0.5 mM K3Fe(CN)6/0.1 M KCl electrolyte at different scan rate and (e), f the corresponding fitting curves