Probing Sulfur-Mediated Surface Dynamics in Oxomolybdate Nano-Rods toward Efficient Oxygen Evolution

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• The oxygen evolution reaction (OER) is crucial for energy conversion technologies.
• Developing efficient and stable electrocatalysts for OER remains a significant challenge.
• Nickel-based compounds are promising OER catalysts, but their performance needs further enhancement.

Purpose of the Study:

• To synthesize sulfur-doped nickel molybdate (S-NiMoO4) via a one-pot hydrothermal method.
• To investigate the effect of sulfur doping on the structural, electronic, and catalytic properties of NiMoO4 for OER.
• To elucidate the mechanism of sulfur's role in enhancing OER activity and stability.

Main Methods:

• One-pot hydrothermal synthesis of S-NiMoO4 catalysts.
• Electrochemical characterization including overpotential, turnover frequency (TOF), and charge transfer resistance measurements.
• X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and other surface analysis techniques.
• Density Functional Theory (DFT) calculations to understand electronic structure and reaction mechanisms.

Main Results:

• Optimized 10% S-NiMoO4 exhibited excellent OER activity with an overpotential of 289 mV at 10 mA cm-2.
• Achieved a high TOF of 0.465 s-1 and low charge transfer resistance (6.6 Ω).
• Sulfur incorporation led to surface reconstruction forming active SO4(2-) species, enhancing OH- adsorption and M-O binding.
• Demonstrated excellent durability (>30 h) and 92% faradaic efficiency.

Conclusions:

• Sulfur doping in NiMoO4 is an effective strategy to enhance OER performance.
• Sulfur plays a dual role in lattice doping and surface reconstruction, creating active sites.
• The S-NiMoO4 catalyst offers a promising pathway for developing robust and efficient anion-modified electrocatalysts for OER.