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[Display omitted] • The ultrathin RhIr NSs/NF was prepared by a simple and mild one-pot aqueous strategy at room temperature. • The unique sheet-like architectures provided large ECSA and exposed high-density active sites. • The self-supported RhIr NSs/NF had excellent HER activity and stability for the HER over a wide pH range. The development of low-cost and high-efficiency electrocatalysts is very important for electrocatalytic hydrogen evolution reaction (HER) in water splitting system. Herein, ultrathin rhodium-iridium nanosheets were facilely in-situ grown on nickel foam (RhIr NSs/NF) by a one-pot aqueous strategy at room temperature. The sheet-like structures with the film thickness of 78 nm were identified by scanning electron microscopy and transmission electron microscopy. The catalyst showed greatly high HER features in both 1.0 M KOH and 0.5 M H 2 SO 4 with the overpotentials of 15 and 14 mV to achieve 10 mA cm−2, respectively, surpassing most Pt-free catalysts. Also, the RhIr NSs/NF exhibited amazing catalytic stability during the long-term operation. This study offers a facile and rational pathway for design and synthesis of advanced HER electrocatalysts for energy conversion devices. [ABSTRACT FROM AUTHOR]

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 x /NF). The unique nanosheets exposed abundant active sites and provided large electrochemically active surface area. The as-built FeCoNiS x /NF exhibited high OER performances with the small overpotentials of 231 and 268 mV to afford 10 and 50 mA cm−2 in 1.0 M KOH, respectively, coupled with a small Tafel slope of 55 mV dec−1. Furthermore, the FeCoNiS x /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. [ABSTRACT FROM AUTHOR]