A chloride-resistant high-potential biocathode based on Trametes hirsuta laccase incorporated into an optimized Os-complex modified redox hydrogel (80 mV potential difference to the T1 Cu) is described. The bioelectrocatalytic activity towards O2 reduction is due to an intimate access of the polymer-bound Os-complex to the T1 Cu site. The chloride resistance of the biocathode is due to the tight binding of the polymer-bound Os-complex to the T1 Cu site.