Rapid Molten-Salt Synthesis of Phase-Controlled Mo-Doped Sulfides for Water Splitting

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Transition metal sulfides are key electrocatalysts for water electrolysis.
• Conventional synthesis methods for these catalysts are often time-consuming.
• Developing efficient and rapid synthesis routes is crucial for practical applications.

Purpose of the Study:

• To develop a novel, rapid, low-temperature molten-salt template approach for fabricating electrocatalysts.
• To synthesize free-standing Mo-doped sulfide nanowire arrays (Mo-Ni₃S₂@Ni₉S₈/NF) on nickel foam (NF).
• To evaluate the electrocatalytic performance of the synthesized material for water electrolysis.

Main Methods:

• One-step fabrication using a rapid low-temperature molten-salt template method (30 min).
• Characterization using X-ray Diffraction (XRD) and Raman spectroscopy.
• Electrochemical measurements including overpotential, stability tests, and electrolyzer performance.
• Density Functional Theory (DFT) calculations for mechanistic insights.

Main Results:

• Successfully synthesized Mo-Ni₃S₂@Ni₉S₈/NF with Mo doping enhancing NiS to Ni₉S₈.
• Achieved low overpotentials: 320 mV for OER (100 mA cm^-2) and 248 mV for HER (50 mA cm^-2).
• Demonstrated excellent stability (>50 h) and efficient bifunctional catalysis in an alkaline electrolyzer (10 mA cm^-2 at 1.51 V).
• DFT calculations confirmed enhanced activity due to optimized hydrogen adsorption and reduced OER overpotential.
• Mo doping promoted the formation of the catalytically superior NiOOH phase during surface reconstruction.

Conclusions:

• The rapid molten-salt method is effective for synthesizing high-performance electrocatalysts.
• Mo-doped Ni₃S₂@Ni₉S₈/NF exhibits superior bifunctional activity and stability for water electrolysis.
• This approach significantly reduces synthesis time, paving the way for practical electrocatalyst production.