Synthesis of Ni3S4/NiS2/FeS2 nanoparticles for hydrogen and oxygen evolution reaction

Highlights: • Ni₃S₄/NiS₂/FeS₂ nanoparticles are constructed by a facile hydrothermal method. • Ni₃S₄/NiS₂/FeS₂ nanoparticles expose the interfacial structures. • Ni₃S₄/NiS₂/FeS₂ nanoparticles show the outstanding overall water splitting activity. • Interfacial structures between Ni-S and Fe-S are accounting for the high activity. Construction of bi-functional noble metal-free catalysts with low cost and high efficiency is greatly desired for hydrogen and oxygen evolution reactions. It is of vital importance to regulate the surface electron state of pyrite to improve the electrocatalytic performance towards overall water splitting. In this work, we provide a simple one-pot interface-regulated strategy to synthesize Ni₃S₄/NiS₂/FeS₂ nanoparticles with exposed interfacial structures between Ni-S and Fe-S, which can then affect the conductivity and activity of pyrite. Notably, Ni₃S₄/NiS₂/FeS₂ nanoparticles are highly active in the hydrogen evolution reaction with 197 mV at 10 mA/cm². Superior oxygen evolution activity is observed for Ni₃S₄/NiS₂/FeS₂ nanoparticles with 1.46 V at 10 mA/cm², outperforming RuO₂ with 1.54 V. Impressively, Ni₃S₄/NiS₂/FeS₂ nanoparticles could efficiently drive water splitting into hydrogen and oxygen at a voltage of 1.68 V at 10 mA/cm² in a two-electrode configuration and robust long-term stability was verified by continuous 20 h i-t tests without apparent loss in the current density. The outstanding catalytic activity could be traced back to the presence of interfacial structures between Ni-S and Fe-S. This work highlights that engineering heteroatoms into pyrite that can trigger the generation of interfacial structures, which beneficially accelerates electron transfer during the water splitting process.