Abstract: This article adopted the composite made up of chitosan and meso-porous carbon doped with nitrogen material which was secured by mechanical mixing as carrier for laccase immobilization. Entrapped laccase based biocathode was prepared by complex with enzyme dripping and coating on the surface of bare glassy carbon electrode and drying process in air consecutively. The direct electrochemical behavior of this as-prepared electrode in the electrolyte without any substrate was investigated, furthermore its catalytic function for oxygen reduction reaction(ORR), its long-term usability, reproducibility and mechanical stability were systematically estimated. On the basis of previous results, performance of this laccase based electrode as oxygen electrochemical sensor was examined. Results from research indicate that the composite composed of meso-porous carbon doped with nitrogen and chitosan with entrapped enzyme modified electrode displays the direct electron transfer between T1 active centre in laccase and the electrode in the absence of any extra electron relay and can catalyze oxygen electrochemical reduction(ORR) under higher potentials. The onset potential for ORR is ～860 mV and the mid-wave current density for ORR is 78×10-12 A/cm2. This laccase based electrode shows excellent reproducibility and desirable long-term stability, but its mechanical stability is inferior. This laccase base electrode was proved to be a suitable sensor for oxygen molecules with the detection limit low to 0.4 μmol/L, the high sensitivity of 67.9×10-6 A·L/mmol and the preferable affinity KM=764.0 μmol/L for oxygen.

Key words: Laccase, direct electron transfer, oxygen reduction reaction, electrochemical sensor