Large charge-storage-capacity iridium/ruthenium oxide coatings as promising material for neural stimulating electrodes

Electrochemical and topographical/structural/morphological properties of thermally prepared Ir/Ru-oxide coatings of various compositions formed on a Ti substrate were investigated. An apparent electrochemically active surface area (AEASA) and charge storage capacity (CSC) were determined. The freshly-prepared Ir0.6Ru0.4-oxide coating was found to offer the largest AEASA and CSC; however, after exposing all the coatings to prolonged extreme electrochemical cycling in phosphate buffered saline pH 7.4, within a 5 V potential window (“torturing”), the Ir0.8Ru0.2-oxide coating yielded both the largest AEASA (1540 cm2) and CSC (27 mC cm−2). Under the same experimental condition, the Ir0.8Ru0.2-oxide coating was found to yield by a 56% higher CSC than the current state-of-the-art neural stimulating electrode, Ir-oxide, making it a good candidate for further optimization and possible application as a neural stimulating electrode.