Etching-Induced Surface Reconstruction of NiMoO₄ for Oxygen Evolution Reaction

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Rational design of oxygen evolution reaction (OER) pre-catalysts is critical for efficient water electrolysis.
• Developing universal OER catalysts with high performance and stability remains a significant challenge.

Purpose of the Study:

• To tailor the electronic structure of NiMoO4 by employing a double-cation etching strategy.
• To enhance the catalytic activity and durability of NiMoO4 for the oxygen evolution reaction.

Main Methods:

• Synthesis of NiMoO4 nanorods followed by etching with hydrogen peroxide (H2O2) to induce cation deficiencies and lattice distortion.
• Computational calculations to investigate the electronic structure changes and active site properties.
• Electrochemical testing to evaluate catalytic performance (overpotential) and long-term durability.
• In situ Raman spectroscopy to probe the formation of active species during catalysis.

Main Results:

• The double-cation etching strategy successfully reconstructed the NiMoO4 surface, creating abundant cation deficiencies and lattice distortion.
• Computational results indicated an upshift of the d-band center for Ni atoms and improved oxygen adsorption capacity at the active sites.
• The optimized catalyst (NMO-30M) demonstrated a low overpotential of 260 mV at 10 mA cm-2 and exceptional durability over 162 hours.
• In situ Raman spectroscopy revealed the rapid formation of high-oxidation-state transition metal hydroxide species, contributing to enhanced catalytic activity.

Conclusions:

• Surface reconstruction via double-cation etching is an effective approach to activate NiMoO4 catalysts for OER.
• The presence of cation deficiencies and lattice distortion significantly improves catalytic performance and stability.
• This study provides insights into catalyst activation mechanisms and offers a pathway for designing advanced OER catalysts.