Unique hybrid Ni2P/MoO2@MoS2 nanomaterials as bifunctional non-noble-metal electro-catalysts for water splitting

Abstract

We successfully synthesized a novel electro-catalyst with a unique structure of Ni₂P nanoparticles decorating the surface of MoO₂@MoS₂ sub-microwires on titanium foil (denote as NiMoO-SP/Ti) via a facile temperature-programmed sulfuration-phosphorization from its nickel molybdate precursor. The metallic MoO₂ core facilitates electron transfer, and the interfaces between MoS₂ nanosheets and Ni₂P nanoparticles enhance catalytic activity both for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Due to this unique structure, the obtained NiMoO-SP/Ti showed an enhanced OER performance in alkaline solution with a small Tafel slope of 85 mV dec⁻¹ and a low overpotential of 280 and 360 mV to achieve 10 and 100 mA cm⁻² in 1.0 M KOH, respectively. The catalyst also exhibited an excellent stability in 1.0 M KOH, with just 12 mV shift after electrolysis at 10 mA cm⁻² for 16 h and 27 mV shift after electrolysis at 20 mA cm⁻² for another 24 h. In addition, the NiMoO-SP/Ti also displayed high catalytic properties towards HER with a small Tafel slope of 77 mV dec⁻¹ and a low overpotential of 159 mV to obtain 10 mA cm⁻² in 1.0 M KOH. After electrolysis at −10 mA cm⁻² for 40 h, the overpotential increased by just 25 mV, which demonstrated its high stability for HER in 1.0 M KOH. This work provides an effective route to designing a high-performance catalyst with a favorable structure for the development of electro-catalysts for water splitting.