Electron transfer processes occurring on platinum neural stimulating electrodes: calculated charge-storage capacities are inaccessible during applied stimulation

OBJECTIVE: Neural prostheses employing platinum electrodes are often constrained by a charge/charge-density parameter known as the Shannon limit. In examining the relationship between charge injection and observed tissue damage, the electrochemistry at the electrode-tissue interface should be considered. The charge-storage capacity (CSC) is often used as a predictor of how much charge an electrode can inject during stimulation, but calculating charge from a steady-state i-E curve (cyclic voltammogram) over the water window misrepresents how electrodes operate during stimulation. We aim to gain insight into why CSC predictions from classic i-E curves overestimate the amount of charge that can be injected during neural stimulation pulsing. APPROACH: In this study, we use a standard electrochemical technique to investigate how platinum electrochemistry depends on the potentials accessed by the electrode and on the electrolyte composition. MAIN RESULTS: ) or proteins (bovine serum albumin) inhibits oxide formation and alters H adsorption. SIGNIFICANCE: These observations help explain why traditional CSC calculations overestimate the charge that can be injected during neural stimulation. The results underscore how careful electrochemical examination of the electrode-electrolyte interface can result in more accurate expectations of electrode performance during applied stimulation.