A self-protection strategy for a bimetallic sulfide nanosheet array achieving ultra-stable oxygen evolution activity...

The use of a water-electrolysis electrode with ultra-stable activity under industrial conditions is a crucial factor to guarantee the long-term operation of an electrolyzer. However, most highly active electrodes suffer from the dissolution of active sites in harsh operating environments. Herein, we have synthesized a large-scale bimetallic sulfide nanoarray (NiFeS) supported on Ni mesh via a spray coating-calcining method. NiFeS exhibits excellent electrochemical performance, delivering a current density of 100 mA cm^-2 at an overpotential of 375 mV without iR correction, outperforming NiS, FeS and NiFeO counterparts. Meanwhile, the NiFeS electrode achieves 500 mA cm^-2 at 2.174 V and 90 °C for water electrolysis and maintains a stable cell voltage at 500 mA cm^-2 over 1000 h. Further characterization studies, including Raman and ICP tests, reveal that the sulfide species in NiFeS transform into SO_x^2- oxyanions during the OER process. The SO_x^2- oxyanions act as an inhibitor to protect the metal active sites from dissolving, which also prevents the cathode from being polluted, ensuring exceptional catalytic ability for long-term operation.