Ti Dopants as a Morphology-Stabilizing Agent in Mesoporous Ruthenium Oxide Electrodes

Due to its excellent electrochemical properties, ruthenium oxide is used in applications ranging from electrocatalysis to sensors and energy storage. However, the scarcity and cost of ruthenium demand strategies for maximizing its efficient use. Primary tools in this are nanostructuring, which enhances the accessible surface area, and crystallization, which improves stability against dissolution. However, these two strategies are typically in conflict: crystallization via high-temperature calcination often leads to pore collapse in nanostructured RuO_<i>x</i>. To deal with this trade-off between porosity and stability, here, we demonstrate that titanium doping stabilizes the mesoporous structure of RuO_<i>x</i> during high-temperature calcination, enabling the synthesis of highly crystalline yet mesoporous RuTiO_<i>x</i> films. Unlike earlier Ti-doped RuO_<i>x</i> systems, which often suffer from a loss of porosity or structural cracking at elevated temperatures, our soft-templated RuTiOx films retain a well-defined mesostructure and exhibit strong electronic interaction between Ti-O and Ru-O bonds. Electrochemical testing shows that the RuTiO_<i>x</i> electrodes exhibit high catalytic activity for the chlorine evolution reaction (CER), achieving current densities above 500 mA cm^-2 at 1.50 V_Ag/AgCl in 3 M HCl, with improved operational stability compared to pure RuO_<i>x</i>. This work highlights a dual role of Ti: stabilizing film morphology and tuning the electronic structure, offering a general strategy to combine high surface area with long-term durability in mesostructured electrocatalysts.