Evaluation of Immobilized Enzyme in a High-Surface-Area Biofuel Cell Electrode Made of Redox-Polymer-Grafted Carbon Black

The current density of biofuel cell needs to be increased by 2 orders of magnitude to reach 10(-1) A cm(-2), which is the required density for portable energy devices. Model calculations have suggested that high-surface-area biofuel cell electrodes can achieve the required current density. However, experimental current density has amounted to only about 10(-3) A cm(-2) because of low enzyme surface coverage. In this study, we investigated the low surface coverage of glucose oxidase (GOD) in a high-surface-area biofuel cell electrode made of redox-polymer-grafted carbon black. Three possible explanations were considered: (i) low total amount of GOD, (ii) poor contact between GOD and mediator in the redox polymer, and (iii) deactivation of GOD. Among them, iii was found to be the main problem. Reducing this deactivation is the key for achieving a current density of approximately 10(-1) A cm(-2).