Sulfurization-Regulated MOF-Derived NiCo2S4/NiCo2O4 Composites Supported on Porous Nitrogen-Doped Carbon for Efficient Alkaline Water Splitting

Abstract

Efficient, stable electrocatalysts made from nonprecious elements are needed to support hydrogen production by alkaline water electrolysis. In this study, electrospun nanofibers serve as the scaffold for a metal–organic framework (MOF)-assisted preparation of NiCo2S4/NiCo2O4 composites on porous nitrogen-doped carbon (NiCo2S4/NiCo2O4/NC). By controlling sulfurization, the proportions of the sulfide and oxide phases were adjusted to improve catalytic activity. In 1.0 M alkaline electrolyte, the optimized NiCo2S4/NiCo2O4/NC-2 sample required overpotentials of 117 mV for the hydrogen evolution reaction (HER) and 227 mV for the oxygen evolution reaction (OER) at 10 mA cm–2. A two-electrode device using this material at both electrodes operated at 1.56 V to reach 10 mA cm–2 and showed favorable stability over 50 h of electrolysis. The performance improvement is attributed to cooperation between the sulfide/oxide phases and conductive carbon, which affects the electronic environment of the catalytic centers, supports charge transport, and makes active interfaces more accessible. This work provides a rational strategy for designing transition-metal-based composite electrocatalysts through anion regulation for efficient alkaline water splitting.