Robust and Efficient Iron-Based Electrodes for Hydrogen Production from Seawater at High Current Density Above 1000 Ma Cm−2

Abstract

The implementation of cheap iron-based catalysts for seawater electrolysis at high- current-density offers an economical and sustainable solution for industrial hydrogen production in near future. However, Fe-based electrodes suffer from poor intrinsic activity and corrosion resistance in seawater, resulting in unsatisfactory seawater splitting performance. Here, we reported the scale-up fabrication of whole-Fe-based electrodes (NiFe-X (X=O, P) NAs/Fe foam) by facile soaking-phosphating. Surface active layers exhibit enhanced corrosion resistance compared to bare Fe foam, and trace Ni modification boosts the intrinsic activity of cathodic NiFeP and in-situ generated anodic NiFeOOH, respectively. The NiFe-P||NiFe-O pair only requires 1.93 V to deliver 3000 mA cm−2 at 6 M KOH, 60 oC for overall seawater splitting, and works stably for 200 h at 1000 mA cm−2. Furthermore, NiFe-X (X=O, P) NAs/Fe foam show impressive adaptation to fresh water/tap water/seawater and all kinds of renewable energies, presenting excellent flexibility for various environmental applications and scenarios.

Keywords: Transition-metal phosphide, Transition-metal oxide/oxyhydroxide, large current density, water/seawater splitting, Sustainable hydrogen production