Electrochemical reduction of hydrogen peroxide by nanostructured hematite modified electrodes

Abstract

In this study, various nanostructured hematites (α-Fe₂O₃), including nanorods (α-Fe₂O_3NR), nanoparticles (α-Fe₂O_3Np), and nanosheets (α-Fe₂O_3NS), were synthesized and their electrocatalytic properties towards the reduction of H₂O₂ were investigated. All nanostructured α-Fe₂O₃ hematites were synthesized using chemical bath deposition (CBD) under mild conditions, followed by thermal treatment at 500 °C. The nanostructure was controlled simply by adjusting the composition of precursor solution and reaction duration for the CBD process. It was found that iron phosphate (FePO₄) was deposited in situ onto the surface of these nanostructured α-Fe₂O₃ hematites during the electrochemical pretreatment in the phosphate electrolyte, and both FePO₄ and α-Fe₂O₃ showed activity in catalysing the electrochemical reduction of H₂O₂. In addition, the interaction/compatibility between deposited FePO₄ and α-Fe₂O₃ has a decisive effect on the overall electrocatalytic activity of the resultant electrodes; FePO₄ only showed a synergetic effect on the overall electrocatalytic activity with α-Fe₂O_3NR and α-Fe₂O_3NS. The rate constant is highest for the electro-reduction of H₂O₂ on FePO₄ modified α-Fe₂O_3NR (α-Fe₂O_3NR|FePO₄), but FePO₄ modified α-Fe₂O_3NS (α-Fe₂O_3NS|FePO₄) showed the best overall electrocatalytic activity due to its relatively higher surface area. Furthermore, dissolved oxygen showed negligible interference on the activity of α-Fe₂O_3NR|FePO₄ and α-Fe₂O_3NS|FePO₄, which makes them promising sensing materials in oxidase-based electrochemical sensors.