Rapid electrochemical processes on stimulating electrodes: double layer and oxygen contributions on gold

The electrochemical behavior of intramuscular stimulating electrodes under normal operating conditions is found to be quite different from what is generally described in the literature. Reaction kinetics appear to play an important role in determining whether a process participates in the faradaic reactions during a stimulus pulse. For H₂ evolution, slow kinetics drive the potential during a 100-μs current pulse over 400 mV negative of the steady-state value. The current studies also reveal that the reversible nature of gold in sulfuric acid is much greater than that described by others for stimulating electrodes. Even when the electrode begins to evolve H₂ , over 70% of the injected charge is reversible within 5 ms. This contrasts with reports indicating that the majority of the charge goes into irreversible reactions such as hydrogen evolution. The difference may result from the use of transient analysis instead of slow sweep methods and the extrapolation of the results to behavior during a normal pulse