Flocculent VS nanoparticle aggregate-modified NiCo2S4 nanograss arrays for electrocatalytic water splitting

Abstract

Despite the fact that electrocatalysis has made great achievement, it is a challenge to design/fabricate efficient and low-cost electrocatalysts for the generation of hydrogen and oxygen through overall water splitting. Here, flocculent VS nanoparticle aggregate-modified NiCo₂S₄ nanograss arrays grown on a nickel foam (denoted as VS/NiCo₂S₄/NF) were fabricated via a hydrothermal method, and were applied as electrodes for overall water splitting. Clearly, the introduction of VS nanoparticle aggregates could modify the electronic structure and offer rich active sites. Moreover, strong electronic interactions between the interfaces of the flocculent VS nanoparticle aggregates and NiCo₂S₄ nanograss arrays could improve the conductivity and charge transfer capability. Thus, the as-prepared VS/NiCo₂S₄/NF exhibits outstanding electrocatalytic activity with overpotentials of 332 mV for OER at the current density of 50 mA cm⁻² and 187 mV for HER at the current density of 10 mA cm⁻² in a 1 M KOH electrolyte, being superior to most of the previously reported Ni/Co-based sulfide electrocatalysts. Besides, the two-electrode system consists of VS/NiCo₂S₄/NF for overall water splitting under alkaline conditions, and it requires 1.87 V to attain 50 mA cm⁻², and maintains this activity for at least 24 h. Our findings could provide an opportunity for the rational design of highly efficient bifunctional composite electrocatalysts towards water splitting.