Stable ‘Floating' Air Diffusion Biocathode Based on Direct Electron Transfer Reactions Between Carbon Particles and High Redox Potential Laccase

Abstract

We report on the assembly and characterisation of a high potential, stable, mediator‐less and cofactor free biocathode based on a fungal laccase (Lc), adsorbed on highly dispersed carbonaceous materials. First, the stability and activity of Trametes hirsuta Lc immobilised on different carbon particles were studied and compared to the solubilised enzyme. Based on the experimental results and a literature analysis, the carbonaceous material BM‐4 was chosen to design efficient and stable biocatalysts for the production of a ‘floating' air diffusion Lc‐based biocathode. Voltammetric characteristics and operational stability of the biocathode were investigated. The current density of oxygen reduction at the motionless biocathode in a quiet, air saturated citrate buffer (100 mM, pH 4.5, 23 °C) reached values as high as 0.3 mA cm–2 already at 0.7 V versus NHE. The operational stability of the biocathode depended on the current density of the device. For example, at low current density (20 μA cm–2), the biocathode lost only 5× of its initial power after 1 month of continuous operation. However, when the device was polarised at 150 mV it lost more than 32× of its initial power in just 10 min. We also found that co‐immobilisation of Lc and peroxidase on highly dispersed carbon materials could protect the biocatalyst from rapid inactivation by hydrogen peroxide produced during electrocatalytic reactions at high‐current densities.

Laccase-Catalyzed Bioelectrochemical Oxidation of Water Assisted with Visible Light

“…70 However, the photoelectrocatalytic properties of the hybrid device were considerably worse than those obtained with high redox potential laccases directly attached to electrodes 41 , which give high catalytic currents of O 2 bioelectroreduction at low overpotentials accompanied with a high operational stability. [44][45][46][47][48][49] Therefore, it is of much interest to develop laccase/semiconductor hybrids as photoelectrocatalysts devices for the reverse reaction, i.e. water oxidation to O 2 .…”

Hydrogen bioelectrooxidation on gold nanoparticle-based electrodes modified by Aquifex aeolicus hydrogenase: Application to hydrogen/oxygen enzymatic biofuel cells

“…Consequently, whereas the bioanode current was almost unchanged after the polarization experiment, the biocathode lost around 50% in current density ( Figure 6A). Attempt to increase the stability of the biocathode by co-immobilization of catalase with Mv BOD as proposed in [49] did not result in an improved stability. Nevertheless, at a cell voltage of 0.8 V a power density of 0.25 mW.cm -2 is reached ( Figure 6C).…”

Design of Carbon Nanotube‐Based Gas‐Diffusion Cathode for O2 Reduction by Multicopper Oxidases

“…The presented design of a gas-diffusion electrode with tethered laccase as biocatalyst of oxygen reduction delivers approximately a current density of 0.5 mA cm −2 (at 0 mV), which is quite comparable to other bio-cathodes. For example a "floating air" laccase cathode achieved current densities of 0.5 mA cm −2 (at 500 mV) [17] and in previous work we reported 1 mA cm −2 (at 0 mV) [20] for an air-breathing laccase cathode. In both cases much higher amounts of laccase were adsorbed to carbon black material without the use of crosslinker.…”