A Four-Electron O₂-Electroreduction Biocatalyst Superior to Platinum and a Biofuel Cell Operating at 0.88 V

TLDR

The bioelectrocatalyst was created by wiring laccase to carbon fiber through an electron‑conducting redox hydrogel, tethering its redox sites with long, flexible spacers to a cross‑linked, hydrated polymer matrix. The wired laccase cathode reduced O₂ to H₂O at 0.5 mA cm⁻² (37 °C, pH 5) with a polarization of only –0.07 V, about one‑fifth that of a platinum cathode, and its tethers boosted the apparent electron‑diffusion coefficient 100‑fold; a miniature glucose‑O₂ biofuel cell using this cathode achieved an operating voltage of 0.88 V, the highest reported for a compartmentless cell.

Abstract

O2 was electroreduced to water, at a true-surface-area-based current density of 0.5 mA cm-2, at 37 degrees C and at pH 5 on a "wired" laccase bioelectrocatalyst-coated carbon fiber cathode. The polarization (potential vs the reversible potential of the O2 /H2O half-cell in the same electrolyte) of the cathode was only -0.07 V, approximately one-fifth of the -0.37 V polarization of a smooth platinum fiber cathode, operating in its optimal electrolyte, 0.5 M H2SO4. The bioelectrocatalyst was formed by "wiring" laccase to carbon through an electron conducting redox hydrogel, its redox functions tethered through long and flexible spacers to its cross-linked and hydrated polymer. Incorporation of the tethers increased the apparent electron diffusion coefficient 100-fold to (7.6 +/- 0.3) x 10-7 cm 2 s-1. A miniature single-compartment glucose-O2 biofuel cell made with the novel cathode operated optimally at 0.88 V, the highest operating voltage for a compartmentless miniature fuel cell.