高効率かつ選択的な塩素電解のためのチタン化コバルト表面上の単原子ルテニウムサイト

The development of efficient, stable, cost-effective catalysts for seawater electrolysis is crucial to achieving carbon neutrality and sustainability. Isolated ruthenium single-atom sites in Ru-O coordination environments are incorporated onto Co₂TiO₄/Ti supports via an electrostatic approach using Ru-ethylenediaminetetraacetic acid (EDTA) complexes, enabling atomic-Ru dispersion through interactions between [Ru(EDTA)]^- and metal hydroxide precursors. The resulting Ru(SA)-Co₂TiO₄/Ti catalyst, with an ultra-low Ru loading of 0.08 mg cm^{- 2} (<0.1%), achieves an overpotential of 26.2 mV at 10 mA cm^{- 2}, a Tafel slope of 39.2 mV dec^{- 1}, and 87% selectivity toward active chlorine in seawater-relevant sodium chloride solutions, outperforming state-of-the-art CER systems while using less Ru. Compared to Ru(NC)-Co₂TiO₄/Ti-prepared by direct RuCl₃ deposition without chelating agents and featuring RuO₂ nanoclusters (NC)-the single-site structure in Ru(SA)-Co₂TiO₄/Ti shows significantly improved atomic utilization and durability. Electrochemical analysis indicates that both catalysts share a rate-determining second electron transfer step, yet Ru(SA)-Co₂TiO₄/Ti exhibits proton-independent CER kinetics across pH 4.5-9. Structural characterization and X-ray absorption spectroscopy (XANES and EXAFS) confirm the presence of oxygen-coordinated, mixed-valence Ru³⁺/Ru⁴⁺ single-atom Ru within the orthorhombic Co₂TiO₄ phase, accompanied by increased Co^δ+ and oxygen vacancies, promoting Cl^- adsorption and facilitating Cl₂ formation via a positive-valent chlorine intermediate.