Nanoscopic Silicon Oxide Overlayers Improve the Performance of Ruthenium Oxide Electrocatalysts Toward the Oxygen Evolution Reaction

Abstract

RuO2 is a highly active electrocatalyst for the oxygen evolution reaction (OER) but is unstable in acidic environments. Herein we investigate the encapsulation of RuO2 nanoparticles with semipermeable, nanoscopic silicon oxide (SiOx) overlayers as a strategy to improve their stability. SiOx encapsulated RuO2 (SiOx|RuO2) electrodes were prepared by drop-casting RuO2 nanoparticles onto glassy carbon substrates followed by deposition of SiOx overlayers of varying thickness by a room temperature photochemical deposition process. The best-performing SiOx|RuO2 electrodes consisted of 2–3 nm thick SiOx overlayers on top of RuO2 particles and 3–7 nm thick SiOx on the glassy carbon substrate. Such electrodes exhibited lower overpotentials relative to bare RuO2 due to an improved electrochemically active surface area while also demonstrating an ability to retain OER activity over time, especially at higher overpotentials. Surprisingly, it was found that the SiOx coating was unable to prevent Ru dissolution, which was found to be proportional to the charge passed and independent of the presence or thickness of the SiOx coating. Thus, other possible explanations for the improved current retention of SiOx|RuO2 electrodes are discussed, including the influences of the overlayer on bubble dynamics and the stability of the underlying glassy carbon substrate.