Exceptionally Robust Face‐Sharing Motifs Enable Efficient and Durable Water Oxidation

Abstract Corner‐sharing oxides usually suffer from structural reconstruction during the bottleneck oxygen‐evolution reaction (OER) in water electrolysis. Therefore, introducing dynamically stable active sites in an alternative structure is urgent but challenging. Here, 1D 5H‐polytype Ba₅Bi_0.25Co_3.75FeO_14−δ oxide with face‐sharing motifs is identified as a highly active and stable candidate for alkaline OER. Benefiting from the stable face‐sharing motifs with three couples of combined bonds, Ba₅Bi_0.25Co_3.75FeO_14−δ can maintain its local structures even under high OER potentials as evidenced by fast operando spectroscopy, contributing to a negligible performance degradation over 110 h. Besides, the higher Co valence and smaller orbital bandgap in Ba₅Bi_0.25Co_3.75FeO_14−δ endow it with a much better electron transport ability than its corner‐sharing counterpart, leading to a distinctly reduced overpotential of 308 mV at 10 mA cm⁻² in 0.1 m KOH. Further mechanism studies show that the short distance between lattice‐oxygen sites in face‐sharing Ba₅Bi_0.25Co_3.75FeO_14−δ can accelerate the deprotonation step (*OOH + OH⁻ = *OO + H₂O + e⁻) via a steric inductive effect to promote lattice‐oxygen participation. In this work, not only is a new 1D face‐sharing oxide with impressive OER performance discovered, but also a rational design of dynamic stable and active sites for sustainable energy systems is inaugurated.