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

Abstract

RuO 2 is a highly active electrocatalyst for the oxygen evolution reaction (OER) but is unstable in acidic environments. Herein we investigate the encapsulation of RuO 2 nanoparticles with semipermeable, nanoscopic silicon oxide (SiO x ) overlayers as a strategy to improve their stability. SiO x encapsulated RuO 2 (SiO x |RuO 2 ) electrodes were prepared by drop-casting RuO 2 nanoparticles onto glassy carbon substrates followed by deposition of SiO x overlayers of varying thickness by a room temperature photochemical deposition process. The best-performing SiO x |RuO 2 electrodes consisted of 2–3 nm thick SiO x overlayers on top of RuO 2 particles and 3–7 nm thick SiO x on the glassy carbon substrate. Such electrodes exhibited lower overpotentials relative to bare RuO 2 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 SiO x 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 SiO x coating. Thus, other possible explanations for the improved current retention of SiO x |RuO 2 electrodes are discussed, including the influences of the overlayer on bubble dynamics and the stability of the underlying glassy carbon substrate.