The preparation of Fe-N-C SANs was based on our previous reports . 100 mg of Fe(NO3)3•9H2O was introduced into 160 mL of methyl alcohol containing 3.39 mg of Zn(NO3)2•6H2O with intense ultrasound for 30 minutes. Following this, another 160 mL of methyl alcohol solution containing 3.94 g of 2-Methylimidazole (2-MeIM) was added to the above solution. Then, the above mixture for 24 hours to obtain a GOx-coated SPE. The CV method was conducted to evaluate the electrochemical properties of modified SPEs. The CV settings were the same as in section 2.5.