Tailoring the facets of Ni3S2 as a bifunctional electrocatalyst for high-performance overall water-splitting

Abstract

Tailoring crystallographic facets is one of the most effective ways to design promising electrocatalytic materials. Herein, for the first time, the asymmetric zigzag structure of {11} faceted Ni₃S₂ is elucidated, which is predicted by DFT calculation to have high electrocatalytic activity for both the hydrogen evolution reaction and oxygen evolution reaction. Such Ni₃S₂ nanostructures are then in situ fabricated on a robust 3D scaffold via a one-step hydrothermal treatment of porous Ni foam in a Na₂S aqueous solution, which effectively avoids the hydrogen brittleness of the Ni foam skeletons and guarantees the robustness of the 3D scaffold. As expected, the as-prepared Ni₃S₂ exhibits appealing catalytic performance for both the hydrogen evolution reaction (η = 189 mV at j = 10 mA cm⁻² with a Tafel slope of 89.3 mV dec⁻¹) and oxygen evolution reaction (η = 296 mV at j = 10 mA cm⁻² with a Tafel slope of 65.1 mV dec⁻¹), which is comparable to that of the commercial noble-metal-based catalyst Pt/C and better than that of the commercial catalyst IrO₂. The self-supported Ni₃S₂ electrodes are further used for overall water-splitting, demonstrating high efficiency and durable stability. This work will provide new insights for tailoring crystallographic facets and fabricating advanced energy materials.