Size Effect of Surface Defects Dictates Reactivity for Nitrogen Electrofixation

Area of Science:

• Catalysis
• Materials Science
• Electrochemistry

Background:

• Electrocatalytic nitrogen reduction reaction (eNRR) is a sustainable method for ammonia (NH3) synthesis.
• Defect engineering in catalysts can improve eNRR but often increases the competing hydrogen evolution reaction (HER), reducing selectivity.

Purpose of the Study:

• To engineer VOx catalysts with systematically tuned defect sizes to establish a structure-activity relationship for eNRR.
• To optimize catalyst design for enhanced ammonia production selectivity.

Main Methods:

• VOx catalysts with varying defect sizes were synthesized and characterized.
• In situ spectroscopy and theoretical calculations were employed to understand reaction mechanisms.
• Electrocatalytic performance was evaluated by measuring ammonia yield rate and Faradaic efficiency.

Main Results:

• Medium-sized defects (1-2 nm) in VOx (VOx-MD) demonstrated optimal electronic properties for N2 adsorption and activation.
• VOx-MD facilitated efficient hydrogenation, leading to high eNRR performance.
• An NH3 yield rate of 81.94 ± 1.45 µg h-1 mg-1 and 31.97 ± 0.75% Faradaic efficiency were achieved at -0.5 V (vs RHE).

Conclusions:

• Defect size critically influences eNRR activity and selectivity.
• Medium-sized defects in VOx provide a promising strategy for designing efficient electrocatalysts for ammonia synthesis.
• This work offers a scalable approach for developing advanced catalysts for competitive electrocatalytic reactions.