Strained-Induced Morphological Reconstruction of RuO₂(110) Thin-Film Electrocatalysts

Strain is a widely used strategy for electrocatalyst engineering. Overstraining, however, can lead to unintentional materials transformation. We investigate the impact of strain on the surface morphology of a rutile RuO₂(110) film grown on a symmetry-matching rutile TiO₂(110) substrate. When the film thickness exceeds 9 nm, the RuO₂ surface relaxes by forming step edges that expose the {011} plane. Density functional theory (DFT) calculation shows that the (011) facet is among the lower energy surfaces of rutile RuO₂, suggesting that this formation incurs minimal energetic penalties. In situ atomic force microscopy (AFM) shows that the film maintains the (110) structure of the terrace during electrochemistry. Inductively coupled plasma-mass spectrometry (ICP-MS) further reveals the insensitivity of the Ru dissolution to strain. Our findings show a strain-relieving pathway via surface reconstruction in RuO₂(110) and provide an example of a strain-relieving mechanism that does not affect dissolution.