Impacts of Surface Reconstruction and Metal Dissolution on Ru_1–<i>x</i>Ti_<i>x</i>O₂ Acidic Oxygen Evolution Electrocatalysts

Improved oxygen evolution reaction (OER) electrocatalysts based on an additional understanding of surface changes that occur upon metal dissolution are needed to enable the efficient use of electrochemical water splitting. This work integrates theoretical and experimental studies of the effects of metal dissolution from the RuO₂ and Ru_1-<i>x</i> Ti _<i>x</i> O₂ surfaces on the OER activity and electrochemical stability. Our computational analysis shows that the energetic barriers for metal dissolution depend highly on the surface site and Ti-substituent location. Metal dissolution induces the formation of new active surface sites with different electronic density distributions. In addition to dissolution-induced changes to the surface composition, electron density changes occur in the interfacial electrolyte components. Surface reconstruction changes the activation barriers for the OER steps. Our experimental analysis of RuO₂ and Ru_0.8Ti_0.2O₂ using a two-step durability test in acidic electrolytes shows that the OER activity, surface, and metal dissolution change over the durability tests. Ti-substitution exhibits improved electrochemical stability with cycling. For RuO₂, changes in the mass activity of RuO₂ with cycling are directly correlated with Ru dissolution and lowering of the electrochemical surface area (ECSA). In contrast, Ru_0.8Ti_0.2O₂ showed a 19 times lower Ru dissolution rate, and metal dissolution results in increasing the ECSA and new active sites. Our STEM and EELS analysis supports that repeated cycling under OER conditions results in surface reconstruction for both RuO₂ and Ru_0.8Ti_0.2O₂, with the formation of a disordered RuO₂ surface and changes to the distribution of Ru and Ti at the Ru_0.8Ti_0.2O₂ surface. The experimentally observed changes in activity and surface structure after cycling are consistent with computational analysis, which shows how metal dissolution may alter the OER activation barriers. Combining experimental and computational insights, this work reveals the effects of metal dissolution on the surface atomic and electronic structure and OER activity and advances our comprehension of metal dissolution dynamics and surface reconstruction, which may have implications for other catalytic processes.