One-year stability for a glucose/oxygen biofuel cell combined with pH reactivation of the laccase/carbon nanotube biocathode

• Glucose biofuel cell exhibits 22% of its initial maximum power after one year.
• Laccase electrodes are inhibited by hydroxide at pH 7 but are reactivated at pH 5.
• Several 1 h discharge cycles during 1 year lead to the total production of 30 mW·h.
• Stability of glucose biofuel cells is limited by the stability of the GOx itself.

This study reports a mixed operational/storage stability of a MWCNT-based glucose biofuel cell (GBFC) over one year. The latter was examined by performing a one hour discharge every day during one month followed by several discharges over a period of 11 months. Under continuous discharge in physiological conditions (5 mM glucose, 37°, pH 7), the GBFC exhibits a 25% power decrease after 1 h of operation. This decrease is mainly due to the deactivation of laccase biocathodes at neutral pH. Nevertheless, the biocathodes can be reversibly reactivated via storage in phosphate buffer (pH 5). Under these conditions, the GBFC finally exhibits 22% of its initial maximum power density after one year at intermittent reactivation/discharge cycles. Although both GBFC electrodes can exhibit one year stability, short-term experiments show that biocathodes are limited by hydroxide inhibition while long-term experiments indicate that bioanodes are likely limited by the stability of the GOx itself. While most of the GBFCs in the literature present stability in the range of several weeks, these results demonstrate the viability of a GBFC for industrial applications in a long period of time.