Oxygen Electroreduction versus Bioelectroreduction: Direct Electron Transfer Approach

Being inspired by a very recent review entitled: “Electrocatalysis and bioelectrocatalysis – Distinction without a difference” and following the general approach employed by Prof. Dr. Schuhmann, in the current work we point to the similarities and differences between oxygen electroreduction and bioelectroreduction processes. To additionally distinct our paper from the recent review we touch on different bioelements, such as redox proteins and living cells, but we still keep a special emphasis on oxidoreductases, biocatalysts par excellence. Moreover, we also exclusively focus on oxygen electroreduction based on direct electron transfer reactions. On the one hand, we corroborate the previously made conclusion regarding intrinsically high activity of the active sites of biological catalysts, especially redox enzymes, which results in mass transfer and heterogeneous electron transfer limited currents from oxygen reducing bioelectrodes. On the other hand, we disagree with the statements regarding the exceptionality of precious metal catalysts, and the notion of a huge trade-off between high activity and stability of non-precious metal catalysts and bioelements. We show that the activity and stability of noble metal based cathodes is very far from perfect, especially when these electrodes operate in complex electrolytes, such as physiological fluids, e.g. human blood.