NiFe pyrophosphate enables long-term alkaline seawater oxidation at an ampere-level current density

Abstract

Seawater electrolysis has potential for scalable hydrogen (H₂) production, yet anode corrosion by chloride ions (Cl⁻) remains a critical challenge. Herein, we present an amorphous NiFe pyrophosphate (P₂O₇⁴⁻) on Ni foam (NiFe-PPi/NF) for long-term alkaline seawater oxidation (ASO). Ex situ and in situ characterizations demonstrate that the in situ released P₂O₇⁴⁻ can act as an anion protective layer, effectively repelling Cl⁻ and safeguarding high-valence active metal sites during ASO. Through surface-anticorrosion design, NiFe-PPi/NF demonstrates stable operation at 1000 mA cm⁻² for over 1000 hours with no loss in activity and requires a low overpotential of just 370 mV to achieve this industrial current density in alkaline seawater. This study offers a valuable strategy for developing corrosion-resistant anodes for ASO.