Elevating Platinum to Volumetric Capacitance: High Surface Area Electrodes through reactive Pt sputtering

Abstract Platinum is the most widespread electrode material used for implantable biomedical and neuroelectronic devices, motivating exploring ways to improve its performance and understand its fundamental properties. Using reactive magnetron sputtering, we prepare PtO x , which upon partial reduction yields a porous thin‐film form of Platinum with favorable properties, notably record‐low impedance values outcompeting other reports for platinum‐based electrodes. We establish that its high electrochemical capacitance scales with thickness, in the way of volumetric capacitor materials like IrO x and poly(3,4‐ethylenedioxythiophene), PEDOT. Unlike these two well‐known analogs, however, we find that PtO x capacitance is not caused by reversible pseudofaradaic reactions but rather due to high surface area. In contrast to IrO x , PtO x is not a reversible valence‐change oxide, but rather a porous form of platinum. Our findings show that this oxygen‐containing form of Pt can place Pt electrodes on a level competitive with IrO x and PEDOT. Due to its relatively low cost and ease of preparation, PtO x can be a good choice for microfabricated bioelectronic devices. This article is protected by copyright. All rights reserved