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. We investigated 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.

Oxide-Encapsulated Ruthenium Oxide Catalysts for Selective Oxygen Evolution in Unbuffered pH-Neutral Seawater

“…Ruthenium oxide (RuO x ) emerges as a potentially cost-effective alternative, although it faces notable stability challenges . Baxter et al investigated SiO x -encapsulated RuO x nanoparticles in a chloride-free 0.5 M H 2 SO 4 electrolyte but encountered challenges related to the instability of the glassy carbon substrate and uncertainty about how ionomers in the catalyst ink impacted catalyst performance . In the current study, we avoid these issues by investigating the effects of model RuO x thin film electrodes, which avoid the need for ionomers and eliminate exposure of the underlying substrate to the electrolyte.…”

“…19 Baxter et al investigated SiO x -encapsulated RuO x nanoparticles in a chloride-free 0.5 M H 2 SO 4 electrolyte but encountered challenges related to the instability of the glassy carbon substrate and uncertainty about how ionomers in the catalyst ink impacted catalyst performance. 36 In the current study, we avoid these issues by investigating the effects of model RuO x thin film electrodes, which avoid the need for ionomers and eliminate exposure of the underlying substrate to the electrolyte. This work furthermore advances knowledge over previous studies by (i) carrying out a side-by-side study of both SiO x and titanium oxide (TiO x ) overlayers on the OER and CER performance of highly active RuO x electrocatalysts in pH-neutral solutions and (ii) using in situ Raman spectroscopy measurements to more directly probe the impacts of oxide encapsulation layers on the ability of buried RuO x active sites to carry out the OER.…”

Oxide Encapsulated Ruthenium Oxide Catalysts for Selective Oxygen Evolution in Unbuffered pH Neutral Seawater

“…investigated encapsulated RuOx nanoparticles in acidic conditions and encountered challenges related to interference with ionomers in the catalyst ink and the instability of the glassy carbon substrate. [36] In the current study, we avoid these issues by investigating the effects of SiOx and titanium oxide (TiOx) encapsulation on the performance of RuOx thin film electrodes, which avoid the need for ionomers and eliminate exposure of the underlying substrate to the electrolyte. RuOx is an ideal candidate to explore the influence of oxide encapsulation on OER and CER in seawater given its ability to evolve oxygen and chlorine during brine oxidation.…”