TiO2-x coatings on vitreous carbon have been prepared by spraying solutions of titanium (IV) n-butoxide, followed by thermal decomposition; their electrochemical responses indicate that the TiO2-x layers are highly porous since the electrochemistry of the Fe(CN)(6)(3-)/Fe(CN)(6)(4-) couple and O-2 show great similarity to that at vitreous carbon. In addition, coatings containing dispersed carbon in TiO2-x on titanium have been fabricated and largely show the electrochemistry of carbon. All surfaces lead to the reduction of oxygen initially to hydrogen peroxide but none show entirely simple behaviour.