Structural Buffer Engineering on Metal Oxide for Long‐Term Stable Seawater Splitting

Abstract Seawater electrolysis is an attractive technique for massive green hydrogen production owing to the dominant advantages of seawater resources, namely low‐cost and limitlessness. However, the oxygen evolution reaction (OER) catalysts will be easily deactivated for severe seawater Cl − permeation and corrosion. Herein, a structural buffer engineering strategy is reported to endow the Co 2 (OH) 3 Cl with long‐term operation stability and a high OER selectivity of ≈99.6% in seawater splitting. The lattice Cl − of Co 2 (OH) 3 Cl can act as the structural buffer, whose continuous leaching during OER can leave vacancies for seawater Cl − invasion, so as to avoid catalyst deactivation. Accordingly, Co 2 (OH) 3 Cl can maintain 99.9% of its initial current density after 60 000 s operation, while that of Co(OH) 2 decays by 52.7% in 7 000 s. Meanwhile, the lattice Cl − of Co 2 (OH) 3 Cl can optimize the binding energy of reaction intermediates on the neighboring OCoO site. Thus, Co 2 (OH) 3 Cl exhibits a current density of 330.5 mA cm –2 at the potential of 1.63 V versus RHE, 45.9 times higher than that of Co(OH) 2 . The structural buffer strategy may be applied to incorporate other metal oxides with suitable anions, and effectively boost their OER activity and stability in alkaline seawater.