CVs of PtCu NC electrode. (a) CVs of PtCu NC electrode in 0.1 M PBS containing 1 mM H2O2 with different scan rates. The inset shows the relationship between the peak current and scan rate. (b) CVs of PtCu NC electrode in 0.1 M PBS with different concentrations of H2O2. The inset shows the dependence of the peak current on the concentration of H2O2.