Mild construction of robust FeS-based electrode for pH-universal hydrogen evolution at industrial current density.

The development of fast and mild preparation of transition metal electrocatalysts for efficient and ultra-stable water electrolysis in wide pH range electrolytes is essential for hydrogen energy supply. Herein, ultrathin and metastable FeS nanolayer self-supported on 3D porous iron foam (IF) substrate is fabricated via one-step mild sulfurization etching for only 2 h to obtain FeS@IF electrode, which achieves efficient and long-term hydrogen evolution in alkaline simulated seawater (1.0 M KOH + 0.5 M NaCl), neutral electrolyte (1.0 M PBS) and other corrosive systems. The overpotentials are only 63 mV and 78 mV to drive 10 mA cm during hydrogen evolution in 1.0 M KOH + 0.5 M NaCl and 1.0 M PBS, respectively. Additionally, the FeS@IF electrode continuously catalyzes for over 600 h at 0.2-0.4 A cm in 1.0 M PBS with negligible performance loss, partly attributed to FeS nanolayer firmly etching on the surface and the formation of corrosion-resistant ultrathin nano fan-like iron sulfide oxide (FeOS). This uniformly-distributed morphology helps to facilitate the interfacial electron transmission between active species and substrate, expose more active sites, and provide moderate channels for the rapid liberation of gas bubbles and mass transfer. This work proposes a novel strategy for developing efficient and stable catalysts for hydrogen production in wide pH range systems.