High Sensitive Microsensor Based on Organic‐Inorganic Composite for Two‐Dimensional Mapping of H 2 O 2 by SECM

The present work describes the development of a selective, sensitive and stable sensing microsensor for scanning electrochemical microscopy (SECM) to measure H 2 O 2 during electrochemical reduction of oxygen. The microsensor is based on graphene and Poly(3,4‐ethylenedioxythiophene) composite as support to iron (III) hexacyanoferrate (II) (PEDOT/graphene/Fe III 4 [Fe II (CN) 6 ] 3 microsensor). The electrochemical properties of the PEDOT/graphene/Fe III 4 [Fe II (CN) 6 ] 3 microsensor were investigated by cyclic voltammetry (CV) and scanning electrochemical microscopy (SECM). The PEDOT/graphene/Fe III 4 [Fe II (CN) 6 ] 3 microsensor showed an excellent electrocatalytic activity toward hydrogen peroxide (H 2 O 2 ) reduction with a diminution of the overpotential of about 500 mV in comparison to the process at a bare gold microelectrode. The microsensor presented excellent performance for two dimensional mapping of H 2 O 2 by SECM in 0.1 mol L −1 phosphate buffer solution (pH 7.0). Under optimized conditions, a linear response range from 1 up to 1000 µmol L −1 was obtained with a sensitivity of 0.08 nA L µmol −1 and limit of detection of 0.5 µmol L −1 .