A lightly Fe-doped (NiS2/MoS2)/carbon nanotube hybrid electrocatalyst film with laser-drilled micropores for stabilized overall water splitting and pH-universal hydrogen evolution reaction

Abstract

Transition metal compounds are considered as competitive candidates for efficient noble-metal-free electrocatalysts in overall water splitting. However, a single material generally fails to maintain simultaneous activities in both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, we developed a hybrid electrocatalyst of a Fe-(NiS₂/MoS₂)/carbon nanotube (CNT) film by combining composite and doping strategies, followed by a microstructure design of laser-drilled micropores, for high-efficiency overall water splitting and pH-universal HER. The charge transfer between MoS₂ and NiS₂ synergistically enhances both the HER and OER, and the light Fe doping further promotes the synergistic effect. The microstructure with periodic pores favors the release of bubbles, ensuring long-term stabilities at both low and large current densities without activity degradation. Consequently, Fe-(NiS₂/MoS₂)/CNT exhibits an ideal voltage, even lower than that of noble-metal electrodes, of 1.51 V at 10 mA cm⁻² for overall water splitting in 1 M KOH, with η₁₀ of the HER/OER at 87/234 mV, respectively. As a cathode, it also delivers low η₁₀ values of 98 mV in 0.5 M H₂SO₄ and 127 mV in 1 M PBS, showing a pH-universal HER activity. Our work provides a comprehensive strategy towards high-efficiency electrocatalysts for overall water splitting, which will find a broad range of green energy applications.