CueO-immobilized porous carbon electrode exhibiting improved performance of electrochemical reduction of dioxygen to water

We report the electro-enzymatic reduction of O2 to water at a current density controlled by the diffusion of the dissolved O2 in rotating disk electrode experiments under a broad pH range between 2 and 8. The electrocatalyst is CueO from Escherichia coli, which belongs to the family of multi-copper oxidases, immobilized on mesoporous carbon supports. The electrons are transferred from the electrode to CueO without an electron transfer mediator. The current density reached a value as high as 12 mA cm−2 at 1 atm O2, 25 °C, and 10,000 rpm on the CueO-modified electrodes. The CueO-modified mesoporous carbon cathode is quite superior to the smooth CueO cathode in the current density, electrode kinetics, pH tolerance, and thermal stability.