Manipulation on active electronic states of metastable phase β-NiMoO₄ for large current density hydrogen evolution

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Non-noble transition metal oxides are earth-abundant but typically show poor catalytic activity for the hydrogen evolution reaction (HER).
• This inertness is attributed to a lack of active electronic states near the Fermi-level.
• Developing strategies to enhance HER activity in these materials is a significant challenge.

Purpose of the Study:

• To activate abundant non-noble transition metal oxides for efficient HER catalysis.
• To stabilize metastable phases and engineer active electronic states.
• To demonstrate a novel non-solvent strategy for material modification.

Main Methods:

• A non-solvent strategy was employed to introduce phosphate substitution into β-NiMoO₄.
• The crystal phase of β-NiMoO₄ was stabilized through phosphate incorporation.
• Electrochemical performance for HER was evaluated in 1 M KOH.

Main Results:

• Phosphate substitution stabilized the metastable β-NiMoO₄ phase, generating crucial active electronic states.
• The modified material exhibited optimal hydrogen adsorption free energy (-0.046 eV) and a low overpotential of -23 mV at 10 mA cm⁻².
• Exceptional long-term stability was observed, maintaining -210 mV overpotential at 1000 mA cm⁻² for 200 hours.

Conclusions:

• Phosphate substitution is a viable method for activating transition metal oxides for HER.
• Stabilizing metastable phases can create abundant active electronic states, boosting catalytic performance.
• This approach offers a promising route for developing efficient and cost-effective HER catalysts.