Template-free solvothermal preparation of ternary FeNi2S4 hollow balloons as RuO2-like efficient electrocatalysts for the oxygen evolution reaction with superior stability

Abstract

Ternary transition metal sulfide hollow structures are promising materials for energy storage and conversion applications. However, their synthetic methods are rather complicated and time-consuming. In this work, for the first time, with FeNi₂S₄ hollow balloons (FNSH) as the quintessential example, a template-free solvothermal method has been developed to synthesize ternary transition metal sulfide hollow balloons. The corresponding formation mechanism is deeply investigated, and the main factors affecting the formation of the hollow balloons are confirmed to be reaction time and temperature. FNSH/graphene aerogel (FNSH/GA) is further fabricated, which has been proven to be a highly efficient electrocatalyst for the oxygen evolution reaction (OER). The FNSH/GA exhibits excellent performance for the OER with a small overpotential of 273 mV at 10 mA cm⁻² in 1.0 M KOH, which is even superior to the typical RuO₂ catalyst. Furthermore, the FNSH/GA maintains the excellent performance for the OER even after a 10 h chronoamperometric test. Moreover, the synthetic method is universal and can be widely extended to other ternary transition metal sulfide hollow balloons.