Synthesis of hierarchically porous Ni foam-supported heazlewoodite Ni3S2 nanorod electrocatalysts for highly efficient oxygen evolution reaction

Abstract

At present, the design of highly efficient and stable oxygen electrocatalysts for water-splitting cells in alkaline medium is predominantly limited by the sluggish kinetics for the oxygen evolution reaction (OER). This study proposes a facile and reproducible synthesis process to nurture the hierarchically porous Ni3S2 arrays on nickel foam (Ni3S2@NF) for use as a catalyst. For the hydrothermal synthesis reaction, ultrathin nanorod heazlewoodite Ni3S2 catalysts on NF is synthesized by controlling the amount of hydrazine (2 mL) and the processing time/temperatures (150 ℃ for 12 h). Due to the hierarchically porous nanorod morphologies, Ni3S2@NF under O2-saturated 1 M KOH aqueous solution shows excellent OER performance, with a low overpotential of 263 mV at a current density of 100 mA‧cm−2 and a Tafel slope of 72 mV‧dec−1. Further, Ni3S2@NF shows stable potential behavior at around 1.521 V under the constant current operation of 50 mA cm−2 for 50 h. Ni3S2@NF also shows negligible performance degradation during the constant current (at 50 mA cm−2 for 50 h) and voltage cycling (1.25–1.65 V for 1000 cycles) tests in a 1 M KOH solution. The excellent catalytic performance of Ni3S2@NF can be attributed to the hierarchically porous and ultrathin nanorod structures, the multi-valence-state character of Ni element, and the synergistic effect of NF, and high intrinsic catalytic active electrocatalysts for the OER.