Ultra-porous titanium nitride as a dual-action supercapacitor for implantable neural interfacing electrodes

Abstract

Frontier applications in implantable neural interfacing have raised the demand for low-impedance, high-chargecapacity electrodes capable of retaining these properties with chronic use. Herein, we evaluate an ultra-porous electrode based on over-stoichiometric titanium nitride for its application as a dual-action supercapacitor. Electrochemical measurements demonstrate both faradaic and non-faradaic capacitive mechanisms operating simultaneously, resulting in very high charge capacity with minimal impedance limitations. These characteristics were maintained over 10,000 charge-discharge cycles without significant loss in performance. Moreover, N-vacancies hypothesized to permit the reversible faradaic reactions on the electrode surface appear to remain stable, indicating that the film is able to renew its supply with each cycle, possibly by outward diffusion of excess N from the bulk and into the surface.