New Insights into Corrosion of Ruthenium and Ruthenium Oxide Nanoparticles in Acidic Media

The dissolution behaviors of Ru and ruthenium oxide nanoparticles in acidic media were studied for the first time using highly sensitive in situ measurements of concentration by inductively coupled plasma mass spectrometry (ICP-MS). Online time- and potential-resolved electrochemical dissolution profiles revealed novel corrosion features (signals) in the potential window from 0 to ∼1.4 V, where known severe dissolution due to the oxygen evolution reaction (OER) takes place. Most of the features follow the thermodynamic changes of the Ru oxidation/reduction state, which consequently trigger so-called transient dissolution. An as-synthesized Ru sample was found to exhibit an order-of-magnitude higher dissolution rate than an electrochemically oxidized amorphous Ru sample. The latter, in turn, dissolved about 10 times faster than rutile RuO2. The observed OER activity was in an inverse relationship with the measured dissolution. Disagreement was found with the general assumption that the onset of the OER should coincide with the onset of Ru dissolution. Interestingly, in all samples, Ru dissolution was observed at about 0.17 V lower potentials than the OER. The present results are relevant for various energy-conversion and -storage devices such as proton-exchange membrane electrolyzers, low-temperature fuel cells, reverse fuel cells, supercapacitors, batteries, and photocatalysts that can contain Ru as an active component.