This study described the bioelectrochemistry of hemoglobin (Hb) immobilized on GC electrode modified by ceria (CeO₂). The characteristics of Hb/CeO₂/Nafion/GC electrode were studied by using electrochemical methods. Hb immobilized on Nafion-CeO₂ film retained its native secondary structure, achieved direct electron transfer with the apparent heterogeneous electron transfer rate constant (k_s) of (0.68±0.09) s^－1 and showed excellent bioelectrocatalytic activity to the reduction of hydrogen peroxide. The electrocatalytic response of the biosensor varied linearly with the H₂O₂ concentration ranging from 2.45 to 19.6 μmol• L^－1, with a detection limit of 1.013 μmol•L^－1 and good long-term stability. In the experiment, CeO₂ showed an excellent biocompatibility and provided a friendly microenvironment for the electron transfer between Hb and GC. The successful practice of CeO₂ modified electrode for the direct electrochemical analysis of proteins and the bioelectrocatalytic activity of enzymes offers an efficient strategy and a new promising platform for the applications of rare earth oxide materials in the field of electrochemical sensors.

Key words: hemoglobin, ceria, hydrogen peroxide, direct electrochemistry