MOF-Derived Urchin-like Co9S8-Ni3S2 Composites on Ni Foam as Efficient Self-Supported Electrocatalysts for Oxygen Evolution Reaction

Abstract

Effective and inexpensive electrocatalysts are significant to improve the performance of oxygen evolution reaction. Facing the bottleneck of slow kinetics of oxygen evolution reaction, it is highly desirable to design the electrocatalyst with high activity, good conductivity, and satisfactory stability. In this work, nickel foam supported hierarchical Co9S8–Ni3S2 composite hollow microspheres were derived from in situ-generative MOF precursors and the subsequent sulfurization process by a simple two-step solvothermal method. The composite microspheres were directly grown on nickel foam without any binder, and nickel foam was used as the nickel source and support material. The morphology and constitution of the series self-supported electrodes were characterized by SEM, TEM, XRD, XPS, and Raman, respectively. The unique porous architecture enriched the electrode with sufficient active surface and helped to reactants and bubble evolved during electrochemical water oxidation. Through tuning the concentration of cobalt source and ligand, the content ratio of Co9S8 and Ni3S2 can be modulated. The heterostructures not only afford active interfaces between the phases but also allow electronic transfer between Co9S8 and Ni3S2. The optimized Co9S8-Ni3S2/NF-0.6 electrode with the highest electrochemical surface area and conductivity shows the best OER performance among the series electrodes in 1 M KOH solution. The overpotential of Co9S8-Ni3S2/NF-0.6 is only 233 mV when the current density is 10 mA cm−2, and corresponding Tafel slope is 116.75 mV dec−1. In addition, the current density of Co9S8-Ni3S2/NF-0.6 electrocatalyst hardly decreased during the 12 h stability measurement. Our approach in this work may provide the future rational design and synthesis of satisfactory OER electrocatalysts.