Cobalt-mediated structural transition: facilitating rapid synthesis and enhanced performance of pyrochlore materials for efficient water electrolysis

Abstract

Vacancies, which inevitably exist in all solids, influence numerous atomic behaviors and material properties and play a crucial role in both synthesis processes and application performance. In this study, we present a successful approach utilizing the flexible transition between [CoO₄] and [CoO₆] polyhedra to modulate the oxygen vacancies for further controlling the formation of ruthenate pyrochlores and enhancing the electrocatalytic performance for the oxygen evolution reaction. During the formation of the pyrochlore phase, the incorporation of [CoO₄] tetrahedra introduces an inherent oxygen deficiency, accompanied by the beneficial transformation of [CoO₄] tetrahedra into [CoO₆] octahedra. It kinetically accelerates the diffusive reaction rate constant by 164 times. On the other hand, during the oxygen evolution process by the lattice oxygen mediated mechanism, the flexible transformation between [CoO₆] octahedra and [CoO₄] tetrahedra in pyrochlores can effectively mitigate lattice distortions and suppress the metal–insulator transition induced by atomic rearrangements, thereby significantly enhancing the service life of this multicomponent electrocatalyst in proton and anion exchange membrane water electrolysis applications.