Incorporating Nitrogen-Doped Graphene Quantum Dots and Ni₃S₂ Nanosheets: A Synergistic Electrocatalyst with Highly Enhanced Activity for Overall Water Splitting

Abstract

A noble-metal-free electrocatalyst is fabricated via in situ formation of nanocomposite of nitrogen-doped graphene quantum dots (NGQDs) and Ni₃ S₂ nanosheets on the Ni foam (Ni₃ S₂ -NGQDs/NF). The resultant Ni₃ S₂ -NGQDs/NF can serve as an active, binder-free, and self-supported catalytic electrode for direct water splitting, which delivers a current density of 10 mA cm^-2 at an overpotential of 216 mV for oxygen evolution reaction and 218 mV for hydrogen evolution reaction in alkaline media. This bifunctional electrocatalyst enables the construction of an alkali electrolyzer with a low cell voltage of 1.58 V versus reversible hydrogen electrode (RHE) at 10 mA cm^-2 . The experimental results and theoretical calculations demonstrate that the synergistic effects of the constructed active interfaces are the key factor for excellent performance. The nanocomposite of NGQDs and Ni₃ S₂ nanosheets can be promising water splitting electrocatalyst for large-scale hydrogen generation or other energy storage and conversion applications.