Operational Stability Assays for Bioelectrodes for Biofuel Cells: Effect of Immobilization Matrix on Laccase Biocathode Stability

One of the main issues of enzymatic biofuel cells is the need to develop stable bioelectrodes. However, there is no standard method to study bioelectrode stability. In this study, laccase and anthracene modified multiwall carbon nanotubes (anth-MWCNTs) were used in conjunction with different immobilization polymers in order to increase the stability of the biocathodes. A series of stability assays were used to understand the operational stability of the biocathode in a biofuel cell environment. The immobilization matrices used in this study were tetrabutyl ammonium bromide modified Nafion (TBAB modified Nafion), octyl modified linear polyethylenimine (C-8-LPEI), and vapor deposited tetramethyl orthosilicate (TMOS) gels. The decrease in activity of the galvanostatic and potentiostatic measurements over a 24 hour period of the TBAB modified Nafion were 4.0 +/- 0.6% and 4.1 +/- 0.4%; C-8-LPEI were 0.7 +/- 0.1% and 9.6 +/- 0.5%; and TMOS were 4.1 +/- 0.1% and 10 +/- 2.0%, respectively. This data show that potentiostatic measurements provide a harsher environment for the enzyme and result in lower stability, as well as showing that the TBAB modified Nafion offers a more stabilizing immobilization strategy compared to the C-8-LPEI or TMOS matrices. (C) 2014 The Electrochemical Society.