Titanium Doping Induced Anisotropic Geometric and Electronic Modifications Improve Acidic Oxygen Evolution Reaction on RuO ₂ (110) Surface

Metal doping has garnered attention as a strategy to enhance the oxygen evolution reaction (OER) activity and stability of Ru-oxides. However, the relationship between the surface structure and OER performance remains poorly understood. In this study, we prepared Ti-doped RuO₂(110) thin films using arc plasma deposition and investigated how Ti doping affects the near-surface structure and OER properties in an acidic environment. Up to 5 at% doped Ti was uniformly incorporated into the films without disrupting the 2-fold symmetry of the (110) surface. However, TiO₂ segregated near the outermost surface at higher doping levels, reducing surface symmetry. Ti doping improved the OER activity and Tafel slope across all doping concentrations, whereas the charge-normalized activity showed that the doping effect included an increase in the surface area. Furthermore, Ti doping markedly suppressed the rise in potential and Ru dissolution during constant-current electrolysis. In-plane X-ray diffraction and total-reflection X-ray absorption fine structure analyses revealed that Ti doping induced anisotropic strain in the RuO₂ crystal and altered the electronic structure of Ru. These findings suggest that Ti doping significantly enhances the activity, stability, and corrosion resistance of the RuO₂(110) surface, driven by synergistic changes in the surface structure, lattice strain, and electronic structure of RuO₂.