A 1.76 V hybrid Zn-O2 biofuel cell with a fungal laccase-carbon cloth biocathode

A hybrid biofuel cell has been constructed based on the Zn anode and O2 biocathode, exploiting fungal Cerrena maxima and Choriolus hirsutus laccases cross-linked onto graphite and microstructured graphitized carbon cloth (GCC) electrodes. Immobilized at the graphite electrodes, laccases exhibited a high similarity in the reaction of direct (in the absence of any mediators) bioelectrocatalytic reduction of O2 starting from 0.7 V vs. Ag/AgCl, pH 5, which was consistent with a 94% structural homology of the laccases. The efficiency of the bioelectrocatalytic reaction was enhanced by immobilizing laccases on the high-surface area GCC, due to the increased surface concentration of the laccase molecules properly orientated for the direct electron transfer reaction within the micro-structured electrode. The hybrid biofuel cell, based on the battery-type Zn anode and oxygen laccase/GCC biocathode yielded the open-circuit voltage Voc of 1.76 V and the short-circuit current density jsc of 4 mA cm−2 in quiescent aerated solutions. A maximum power density of the cell was 0.44 mW cm−2 at the cell voltage of 0.5 V, pH 5. The hybrid biofuel cell exploiting cross-linked stabilized laccases at GCC was able to power a 1.5 V domestic device for 38 days.

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► Laccase coupled to carbon cloth is efficient and simple biocathode for biofuel cells.
► Microstructured carbon cloth electrodes allow strong bioelectrocatalysis enhancement.
► Laccase crosslinking provides long-term operational stability of the biocathode.
► Zn/O2 biobattery yields 0.44 mW cm−2 in stagnant aerated solutions.