Bioelectrocatalytic O2 reduction with a laccase-bearing poly(3-methylthiophene) film based on direct electron transfer from the polymer to laccase

Abstract

This communication reports on O2 reduction with a biocathode composed of poly(3-methylthiophene) (P3MT) and laccase based on direct electron transfer (DET). The biocathode was fabricated simply by adsorption of laccase on a P3MT film which was formed on a gold electrode by electrochemical polymerization. Properties of the biocathode were examined by measuring steady-state currents at an arbitrary potential in buffer solutions saturated with O2 or N2 at room temperature. Efficient O2 reduction was achieved with the biocathode, which was attributed to DET from the P3MT film to laccase. The biocathode gave the O2 reduction current density of −150μA/cm2 at +0.40V (vs. Ag/AgCl). The onset potential of O2 reduction was +0.64±0.01V (vs. Ag/AgCl) at pH4.5. The O2 reduction current became maximum in the pH range 4.0–5.0. This pH dependency of the O2 reduction current is corresponding to that of the activity of native laccase. In addition, the O2 reduction current increased markedly with increasing amount of the charge passed through in the formation of the P3MT film.