Towards identifying the active sites on RuO₂(110) in catalyzing oxygen evolution

Abstract

Surface structural transitions and active sites are identified using X-ray scattering and density functional theory.

Ruthenium Oxide Nanosheets for Enhanced Oxygen Evolution Catalysis in Acidic Medium

“…Intriguingly, higher oxidized surface terminations with adsorbed hydroperoxo (OOH) or superoxo (OO) groups are very unfavorable at the nanosheet surface, cf. However, higher oxidized structures such as *O/*O and *OOH/*O quickly gain stability with increasing potential and start to become most stable at potentials around U ≈1.5 V. As expected from the lower coordination of the edge sites, this is now much more similar to results obtained for the rutile (110) surface by Rao et al [29] Nevertheless, highly oxidized edge terminations like fully covered hydroperoxo (*OOH/*OOH) and superoxo (*OO/*OO) are still unfavorable (see blue lines in Figure 5a,b), clearly distinguishing the nanosheet edge from the low-index rutile surfaces. This is in strong contrast to the situation at rutile RuO 2 surfaces, where such higher oxidation intermediates at the surface are much more stable and correspondingly dominate the resting state of the surface even in the OER regime.…”

“…A symmetric two-nanosheet model (Figure 5c) and four O 3f atoms at the inner face between the sheets, which allows assessing H coverages in 25% steps at both O 3f types. [29] We attribute this qualitative difference to the different crystallographic structure of the nanosheet surface and the low-index facets of rutile, in particular to the much studied (110) facet. The determined relative stabilities of the energetically most preferable terminations are plotted in Figure 5a.…”

“…[29] We attribute this qualitative difference to the different crystallographic structure of the nanosheet surface and the low-index facets of rutile, in particular to the much studied (110) facet. [29,33] This confirms the sheet edge as a highly active OER zone, while refined microkinetic studies [34] are required to quantitatively determine the full mechanism behind the extraordinarily high activity measured for the nanosheets. In addition, in particular at the rutile (110) surface the trenchlike structure with protruding O br rows allows to further stabilize OOH and OO groups adsorbed at the lower so-called coordinatively unsaturated (cus) sites through hydrogen-bridge bonds.…”

“…All possible combinations from 0% to 100% H coverages both at surface and interface regions, corresponding to RuOOH x with x = 0, 0.5, 1.0, and 2, have been explored. [29] The low stability of the peroxo species disfavors any OER mechanism at the nanosheet surface involving this species. As expected, hydrogencontaining terminations, corresponding to lower valence states of Ru, become less favorable with increasing potential.…”

Hollow‐Structured Metal Oxides as Oxygen‐Related Catalysts

“…It is beneficial for transporting carriers which endow rutile with excellent oxygen-related catalytic activity, as shown in Tables 1 and 2. [62] For RuO 2 , its OER activities keep increase followed by (101), (001), and (111) facet. Recently, Yang et al found that (100) surface of IrO 2 and RuO 2 showed a more active in alkaline environments than the most thermodynamically stable (110) surface.…”