High-efficiency overall alkaline seawater splitting: using a nickel–iron sulfide nanosheet array as a bifunctional electrocatalyst

Abstract

The use of large-current-density electrolysis of seawater is promising for a massive hydrogen (H₂) production. This process, however, requires high-performance and cost-effective bifunctional catalysts for the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER). Herein, a nickel–iron sulfide nanosheet array on nickel foam (NiFeS/NF) is demonstrated to be a superb bifunctional electrocatalyst for seawater splitting, delivering the industrially demanded current density of 500 mA cm⁻² at overpotentials of 300 and 347 mV for OER and HER in alkaline seawater, respectively. Moreover, its corresponding two-electrode electrolyzer only requires a cell voltage of 1.85 V to drive 500 mA cm⁻² and shows a strong stability for at least 50 h of electrolysis in alkaline seawater, outperforming the most recently reported seawater-splitting catalyst electrodes.