Structural evolution and self-reconstruction of nickel hexacyanoferrate Prussian blue analogues for long-lasting ampere-current seawater oxidation

Abstract

The commercial success of hydrogen (H₂) production via seawater electrolysis largely depends on overcoming anode corrosion caused by chloride (Cl⁻), a critical challenge for scaling up renewable energy storage. Herein, we present the synthesis of nickel hexacyanoferrate Prussian blue analogues via anodic polarization for efficient alkaline seawater oxidation (ASO). Electrochemical experiments and in situ Raman studies unveil that leaching of Fe(CN)₆³⁻ from the electrode facilitates a dynamic self-reconstruction process and leads to the formation of high-valence metal reaction specie, and appropriate Fe(CN)₆³⁻ effectively shields active sites from Cl⁻ interference even at ampere-level current density (j). In experiments, our electrode demonstrates an overpotential of merely 349 mV to reach a j of 1 A cm⁻² and maintains stable operation for over 1000 h with protective Fe(CN)₆³⁻. This work showcases the potential of Prussian blue analogues for efficient and long-lasting ASO, protecting against Cl⁻ in large-scale seawater H₂ electrolysis.