Metal-organic framework-derived CoS2@FeS2 heterostructure with synergistic electronic modulation for oxygen evolution...

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Advancing green hydrogen production necessitates high-performance, earth-abundant electrocatalysts for the oxygen evolution reaction (OER).
• Current catalysts often rely on precious metals or lack the stability and efficiency required for large-scale applications.

Purpose of the Study:

• To rationally design and synthesize an earth-abundant, high-performance electrocatalyst for the oxygen evolution reaction (OER).
• To investigate the synergistic effects of a CoS2@FeS2 heterostructure derived from a metal-organic framework (MOF) for enhanced catalytic activity and stability.
• To elucidate the distinct roles of Cobalt (Co) and Iron (Fe) in the catalytic mechanism and durability.

Main Methods:

• Synthesis of a CoS2@FeS2 heterostructure via one-step sulfidation of a nitro-functionalized Co-based MOF (Co-MOF-NO2).
• Characterization of the material's structure, composition, and porosity using various techniques.
• Electrochemical evaluation of the catalyst's performance for OER in 1.0 M KOH, including overpotential, Tafel slope, and charge transfer resistance measurements.
• In situ Raman spectroscopy and post-OER characterization to understand the catalytic mechanism and surface evolution.

Main Results:

• The optimized CoS2@FeS2 catalyst exhibited a low OER overpotential (239 mV at 10 mA cm⁻²), a small Tafel slope (65.4 mV dec⁻¹), and low charge transfer resistance (0.434 Ω).
• The catalyst demonstrated excellent long-term stability with negligible potential decay over 50 hours of continuous operation.
• In situ studies revealed selective surface reconstruction of Co sites to CoOOH, while Fe acted as an electronic modulator, leading to a unique crystalline-FeS2-core/amorphous-CoOOH-shell structure.

Conclusions:

• The MOF-derived CoS2@FeS2 heterostructure is a highly efficient and stable electrocatalyst for the oxygen evolution reaction.
• The synergistic interaction between CoS2 and FeS2, along with the N,S-doped carbon matrix, significantly enhances catalytic performance.
• This work provides a facile strategy for fabricating bimetallic sulfide heterostructures and offers crucial mechanistic insights for designing advanced non-precious metal OER catalysts.