Electrochemical modification of ITO with Di-(3-diaminorpropyl)-viologen and its electrocatalytic behavior of the oxygen reduction reaction in an alkaline solution

Abstract

We present a Di-(3-diaminopropyl)-viologen cation radical (DAPV(+)center dot) modified ITO electrode prepared by an electrochemical reduction of DAPV(2+) in an aqueous solution and its electrocatalytic behavior for the oxygen reduction reaction (ORR). Electrochemically reduced DAPV(+)center dot was self-assembled on an ITO surface, and cyclic voltammograms (CVs) show an EC-typed voltammetric shape induced by the electrochemical reduction of DAPV(2+). A surface coverage of adsorbed DAPV(+)center dot (DAPV(+)center dot(ads)) on an ITO surface, which was formed by scanning a potential from 020 to -0.55 V for 1000 cycles (DAPV(1000)-ITO) was estimated to 5.1 x 10(-10) mol/cm(2), and DAPV(+)center dot(ads) on an ITO surface was spectroscopically and topographically identified. DAPV(+)center dot(ads) on an ITO surface did not show any blocking effect on 1e(-) transfer in an outer sphere, Fc/Fc(+) redox reaction. However, an electrochemical activity for the ORR in a 0.1 M KOH solution was enhanced in order of a DAPV(100)-ITO, DAPV(500)-ITO, and DAPV(1000)-ITO electrode. An electron number in the ORR obtained from a DAPV(1000)-ITO electrode was estimated to 2, indicating that a DAPV(+)center dot modified ITO electrode electrochemically mediates 2e(-) transfer pathway for the ORR in the alkaline aqueous solution.