The use of potassium ferricyanide leads to a low overpotential of the carbon cathode, and allows the MFC to work close to open circuit potential. The use of ferricyanide outside the laboratory is not practical due to toxicity and insufficient reoxidation by oxygen requiring the catholyte to be regularly replaced [87,134]. Furthermore the use of catalysts, such as platinum or other non-precious metals [81,82], may also be cost inhibitory for large-scale applications and not suitable for long-term applications. In the search for a suitable catalyst for oxygen reduction in a MFC system research is investigating the use of a biocathode.