Rationalizing Synergic Role of Ti─O─Ru Distortion and Ferromagnetic Superexchange Coupling for Envisaging Electrocatalytic Oxygen Evolution Activity in Double Perovskite

ABSTRACT A clear understanding of the activity descriptors governing the oxygen evolution reaction (OER) mechanism in 3 d –4 d transition metal‐based complex oxide system is essential for the rational design of advanced OER electrocatalysts toward green energy and sustainability. To address this uncover goal, herein, we have synthesized a new double perovskite (DP) oxide i.e., Ca ₂ TiRuO ₆ ( CTRO ) which can offer the choice of specific active metal sites to perform and enhance the electrocatalytic OER activity in the variable pH conditions. When this low‐Ru‐content CTRO DP oxide is employed as an active electrocatalyst for the OER, it exhibits an overpotential of 273 mV, which further decreased to 245 mV upon incorporation with a small amount of conducting Vulcan carbon (15 wt.%) at pH 13.8, maintaining excellent durability over 100 h with a remarkable Faradic efficency of 92.4%. The formation of high‐valent Ru–oxo‐hydroxy species, which facilitate the OER through the adsorbate evolution mechanism (AEM), is corroborated by in situ Raman spectroscopic and ex situ ATR‐FTIR studies for the title catalyst. Notably, the higher octahedral distortion of Ti─O─Ru linkage and subtle role of Ru‐sites over the Ti‐sites arising from the ferromagnetic superexchange coupling of Ru (IV)‐ions in the present disordered DP structure contribute to the superior OER activity over other state‐of‐the‐art oxide electrocatalysts. Moreover, in‐depth DFT studies was performed to elucidate ferromagnetic superexchange interactions and to explore the active OER sites along with the energetically favorable H ₂ O adsorption mechanism across various surface terminations in the CTRO catalyst.