Stabilizing active sites of non-iridium-based oxygen evolution reaction (OER) electrocatalysts is crucial, but remains a big challenge for hydrogen production by acidic water splitting. Here, we report that non-stoichiometric Ti oxides (TiO_x) can safeguard the Ru sites through structural-confinement and charge-redistribution, thereby extending the catalyst lifetime in acid by 10 orders of magnitude longer compared to that of the stoichiometric one (Ru/TiO₂). By exploiting the redox interaction-engaged strategy, the in situ growth of TiO_x on Ti foam and the loading of Ru nanoparticles are realized in one step. The as-synthesized binder-free Ru/TiO_x catalyst exhibits low OER overpotentials of 174 and 265 mV at 10 and 500 mA cm⁻², respectively. Experimental characterizations and theoretical calculations confirm that TiO_x stabilizes the Ru active center, enabling operation at 10 mA cm⁻² for over 37 days. This work opens an avenue of using non-stoichiometric compounds as stable and active materials for energy technologies.