Walnut kernel-like iron-cobalt-nickel sulfide nanosheets directly grown on nickel foam: A binder-free electrocatalyst for high-efficiency oxygen evolution reaction.

Developing earth-rich and high-efficiency nonprecious metal catalysts is critical but extremely challenging for oxygen evolution reaction (OER). Herein, a simple room-temperature sulfuration method was developed for in situ synthesis of walnut kernel-like iron-cobalt-nickel sulfide nanosheets on nickel foam (FeCoNiS/NF). The unique nanosheets exposed abundant active sites and provided large electrochemically active surface area. The as-built FeCoNiS/NF exhibited high OER performances with the small overpotentials of 231 and 268 mV to afford 10 and 50 mA cm in 1.0 M KOH, respectively, coupled with a small Tafel slope of 55 mV dec. Furthermore, the FeCoNiS/NF acted as the anode towards overall water electrolysis with acceptable results, where commercial Pt/C dropped on the NF worked as the cathode. This study provides some valuable insights for rational construction of nonprecious electrocatalysts in electrochemical energy technologies.