Mn-incorporated high-entropy quaternary sulfide CoNiFeMnS for efficient electrocatalytic oxygen evolution reaction

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Electrochemical water splitting offers sustainable hydrogen production but is hindered by slow oxygen evolution reaction (OER) kinetics.
• Noble-metal catalysts (e.g., RuO2, IrO2) are effective but expensive and lack durability, necessitating research into alternative materials.
• High-entropy sulfides (HESs) present a promising class of noble-metal-free catalysts due to their stability, tunable electronic properties, and numerous active sites.

Purpose of the Study:

• To synthesize and characterize a novel manganese-doped quaternary high-entropy sulfide (CoNiFeMnS) catalyst.
• To investigate the role of manganese doping in enhancing the catalytic activity and stability for the oxygen evolution reaction (OER).
• To provide a scalable synthesis route and mechanistic insights for designing advanced OER catalysts.

Main Methods:

• A two-step coprecipitation-solvothermal strategy was employed using a CoNiFeMn high-entropy metal-organic framework (HEMOF) precursor.
• Material characterization techniques (e.g., XRD, SEM, TEM) were used to confirm the structure, composition, and morphology of the synthesized HES.
• Electrochemical testing, including cyclic voltammetry and chronoamperometry, was performed to evaluate OER performance and stability.

Main Results:

• Uniform manganese doping was achieved within the face-centered cubic (fcc) structure of the CoNiFeMnS HES, resulting in a micropolygonal morphology.
• Manganese doping modulated the electronic structure, creating highly active nickel centers and significantly reducing the OER overpotential from 301 mV to 208 mV at 10 mA cm-2 compared to the manganese-free counterpart.
• The catalyst exhibited excellent OER performance with a low Tafel slope (65.19 mV dec-1), enhanced double-layer capacitance (12.15 mF cm-2), reduced charge-transfer resistance (141.1 Ω), and remarkable stability over 80 hours.

Conclusions:

• The fabricated Mn-doped CoNiFeMnS HES is a highly efficient and stable noble-metal-free catalyst for the oxygen evolution reaction.
• Manganese doping plays a crucial role in optimizing the electronic structure and enhancing OER activity, offering a valuable strategy for catalyst design.
• The study presents a scalable synthesis approach for Mn-doped HESs, paving the way for practical applications in sustainable hydrogen production.