Iron oxide nanorods array in electrochemical detection of H2O2

Nanorod arrays (NRs) of β-FeOOH, γ-Fe2O3, and α-Fe2O3 were synthesized, and their electrocatalytic properties toward the reduction of H2O2 were investigated. In phosphate electrolyte, iron phosphate (FePO4) was in situ deposited onto these iron oxides during pretreatment, and the interaction between iron oxides and the deposited FePO4 played an important role in determining the electrocatalytic activity of the resultant electrodes. It was found that the redox reaction of FePO4 is more facile on α-Fe2O3NR, and the resultant FePO4 modified α-Fe2O3NR showed best electrocatalytic activity toward the reduction of H2O2. In addition, α-Fe2O3NR showed two reduction peaks in phosphate electrolyte containing 1.66 mM H2O2, one being pH-dependent and related to the electrocatalytic properties of FePO4, and the other one being pH-independent and only related to the intrinsic electrocatalytic properties of α-Fe2O3NR. However, all iron oxides showed only one pH-independent reductive peak in non-phosphate electrolyte containing H2O2. The sensing mechanisms in both conditions are proposed. Under optimized condition, α-Fe2O3NR exhibited excellent sensing characteristics, including a high sensitivity of 181 μA mM−1 cm−2, a wide linear range up to 2.5 mM, a low detection limit of 1.3 μM, and high selectivity against some common biomolecules, which indicates its applicability as a reliable electrochemical H2O2 sensor.