Surface-derived phosphate layer on NiFe-layered double hydroxide realizes stable seawater oxidation at the current density of 1 A°cm−2

Seawater electrolysis, especially in coastlines, is widely considered as a sustainable way of making clean and high-purity H2 from renewable energy; however, the practical viability is challenged severely by the limited anode durability resulting from side reactions of chlorine species. Herein, we report an effective Cl− blocking barrier of NiFe-layer double hydroxide (NiFe-LDH) to harmful chlorine chemistry during alkaline seawater oxidation (ASO), a pre-formed surface-derived NiFe-phosphate (Pi) outer-layer. Specifically, the PO43−-enriched outer-layer is capable of physically and electrostatically inhibiting Cl− adsorption, which protects active Ni3+ sites during ASO. The NiFe-LDH with the NiFe-Pi outer-layer (NiFe-LDH@NiFe-Pi) exhibits higher current densities (j) and lower overpotentials to afford 1 A·cm−2 (η1000 of 370 mV versus η1000 of 420 mV) than the NiFe-LDH in 1 M KOH + seawater. Notably, the NiFe-LDH@NiFe-Pi also demonstrates longer-term electrochemical durability than NiFe-LDH, attaining 100-h duration at the j of 1 A·cm−2. Additionally, the importance of surface-derived PO43−-enriched outer-layer in protecting the active centers, γ-NiOOH, is explained by ex situ characterizations and in situ electrochemical spectroscopic studies.