Trends in Activity and Dissolution on RuO₂ under Oxygen Evolution Conditions: Particles versus Well-Defined Extended Surfaces

Abstract

Rutile RuO2 catalysts are the most active pure metal oxides for oxygen evolution; however, they are also unstable towards dissolution. Herein, we study the catalytic activity and stability of oriented thin films of RuO2 with the (111), (101) and (001) orientations, in comparison to a (110) single crystal and commercial nanoparticles. These surfaces were all tested in aqueous solutions 0.05 M H2SO4. The initial catalyst activity ranked as follows: (001) > (101) > (111) ≈ (110). We complemented our activity data with inductively coupled plasma mass spectroscopy (ICP-MS), to measure Ru dissolution products occurring in parallel to oxygen evolution. In contrast to earlier reports, we find that, under our experimental conditions, there is no correlation between the activity and stability.

The role of metastability in enhancing water-oxidation activity

“…While previous studies [3][4][5] suggest that active dissolution of the material results in the best activities, our results suggest that an activity enhancement can be achieved by an initial dissolution (preconditioning) that creates the variety of reaction sites but that the dissolution does not have to continue for high OER activities. This agrees with recent experimental findings for RuO2 thin films, which show that while the surface orientation with the initially highest dissolution rate results in the best activities, an ongoing dissolution is not necessary for highly active surfaces 6 . It was also reported that the binding energy of reaction intermediates is not a good descriptor for the activity of metastable materials 5 .…”

Ruthenium Nanoparticles on Cobalt‐Doped 1T′ Phase MoS2 Nanosheets for Overall Water Splitting

“…[ 38,53 ] The higher OER catalytic activity of CoRu–MoS 2 than that of Co–MoS 2 is ascribed to the RuO 2 nanoparticles, since this oxide is a well‐known active OER catalyst. [ 54,55 ] The Ru–MoS 2 , in contrast, did not show any activity due to the negligible oxidation of Ru into RuO 2 . Therefore, we suggest that the Co dopant induces the formation of RuO 2 by following the redox reactions of Co 3+ + e − → Co 2+ ( E ° = 1.92 V) and Ru(s) + 2H 2 O(l) → RuO 2 (s) + 4H + + 4e − ( E ° = −0.68 V).…”

Activity‐Stability Volcano Plots for Material Optimization in Electrocatalysis

“…Beyond, the applied overpotential might provide further evidence for the separated apexes: RuO 2 faces severe stability problem under harsh anodic reaction conditions, which is ascribed to the increasing OER current if the applied overpotential is raised. In the overpotential regime of η CER <0.125 V in an acidic electrolyte solution (pH<1) it has been demonstrated by online electrochemical mass spectrometry (OLEMS) that the current affiliated with oxygen evolution is negligible small .…”