Engineering FeOOH/Ni(OH) 2 heterostructures on Ni 3 S 2 surface to enhance seawater splitting

Abstract The construction of highly stable and efficient electrocatalysts is desirable for seawater splitting but remains challenging due to the high concentration of Cl − in seawater. Herein, FeOOH/Ni(OH) 2 heterostructure supported on Ni 3 S 2 ‐covered nickel foam (Fe–Ni/Ni 3 S 2 /NF) was fabricated by hydrothermal and etching methods, as well as anodic oxidation process. The electronic structure of FeOOH and Ni(OH) 2 could be modulated after depositing FeOOH nanoparticles on Ni(OH) 2 nanosheet, which greatly boosted the catalytic activity. When the catalyst used as an electrode for oxygen evolution reaction (OER), it needed low overpotentials of 266 and 368 mV to achieve current densities of 100 and 800 mA·cm −2 , respectively, in 1 mol·L −1 KOH + seawater electrolyte. It can operate continuously at 100 mA·cm −2 for 400 h without obvious decay. Particularly, in situ generated SO 4 2− from inner Ni 3 S 2 during electrolysis process would accumulate on the surface of active sites to form passivation layers to repel Cl − , which seemed to be responsible for superior stability. The study not only synthesizes an OER catalyst for highly selective and stable seawater splitting, but also gives a novel approach for industrial hydrogen production.