An implantable electrode, for an implantable tissue stimulator, has an electrically conductive porous material comprising metal carbide, metal nitride, metal carbonitride, metal oxide or metal oxynitride and one or more coating layers on a surface thereof. The coating layer or at least one of the coating layers, is for contact with body tissue when the electrode is implanted. Each coating layer is an electrically conductive layer of polymer having a polypyrrole polymeric backbone or polythiophene polymeric backbone. The coating layer or layers are formed in situ by electropolymerisation. The polypyrrole or polythiophene may be substituted. The coating layer or layers can provide high charge storage capacitance and a fast discharging profile, as well as biocompatibility.
