One-pot synthesis and microstructure analysis of Fe-doped NiS2 for efficient oxygen evolution electrocatalysis

Abstract

The development of low-cost and effective electrocatalysts for water splitting is important for the production and application of green hydrogen as a renewable energy source. In this work, Fe-doped NiS₂ with different doping contents was successfully prepared through a one-pot solvothermal process utilizing a PEGylated deep eutectic solvent. The morphology, microstructure, electronic structure and oxygen evolution reaction (OER) catalytic activity of the synthesized samples are systematically investigated. The sample with an Fe content of ∼16% possesses the best electrocatalytic performance with a low overpotential of 257 mV at 10 mA cm⁻², a small Tafel slope of 41 mV dec⁻¹ and a superior stability for 60 h at ∼20 mA cm⁻². Stable and homogenous Ni(Fe) oxide porous nanostructures with residual S, including pores of several nanometers, were found after the long-term OER test. X-Ray photoelectron spectroscopy and electron energy loss spectroscopy mapping indicate that the enhanced OER property may be attributed to the local composition variation of Fe at the nanoscale and the synergic effect of Fe and Ni. This study provides insights into the rational design and synthesis of superior transition-metal based water splitting electrocatalysts.