“…Therein, I pa is the oxidation current peak (A), A is the effective surface area of the electrode (cm 2 ), D is the diffusion coefficient of [Fe(CN) 6 ] 3−/4− (6.3 × 10 −6 cm 2 s −1 ), n is the number of electron transfers ( n = 1), v is the scanning rate (V s −1 ), and c is the volumetric concentration of [Fe(CN) 6 ] 3−/4− (mol cm −3 ). 40 According to the formula, the average electroactive surface areas of the GCE, Fe 3 O 4 @Au/GCE, [P 2 W 17 V/PEI] 4 /GCE, and [P 2 W 17 V/PEI] 4 /Fe 3 O 4 @Au/GCE are 0.0456 cm 2 , 0.0509 cm 2 , 0.0483 cm 2 , and 0.0522 cm 2 , respectively. This indicated that the [P 2 W 17 V/PEI] 4 /Fe 3 O 4 @Au/GCE has a more electrically active surface area, which significantly enhances the current response and redox reaction rate.…”