Direct electrochemistry and bioelectrocatalysis of hemoglobin immobilized on carbon black

It is reported for the first time that hemoglobin (Hb) was immobilized on the surface of carbon black powders modified at the surface of a glassy carbon electrode. The cyclic voltammetric results showed that the immobilized Hb could undergo a direct quasi-reversible electrochemical reaction. Its formal potential, E0, is − 0.330 V in phosphate buffer solution (pH 6.9) at a scan rate of 100 mV/s and is almost independent of the scan rate in the range of 40–200 mV/s. The dependence of E0, on the pH of the buffer solution indicated that the conversion of Hb–Fe(III)/Hb–Fe(II) is a one-electron-transfer reaction process coupled with one-proton-transfer. The experimental results also demonstrated that the immobilized Hb retained its bioelectrocatalytic activity for the reduction of H2O2. Furthermore, the immobilized Hb can be stored at 4 °C for several weeks without any loss of the enzyme activity. Thus, the immobilized Hb may be used as a biocathodic catalyst in biofuel cells.