Defective 2D silicon phosphide monolayers for the nitrogen reduction reaction: a DFT study

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Electrochemical nitrogen reduction reaction (ENRR) offers a sustainable route for ammonia synthesis.
• Developing efficient and selective catalysts for ENRR remains a significant challenge.
• 2D materials are emerging as promising platforms for catalytic applications.

Purpose of the Study:

• To investigate the potential of 2D silicon phosphide (SiP) as a catalyst for ENRR.
• To evaluate the effect of a phosphorus defect on SiP's catalytic performance.
• To explore the mechanism and selectivity of nitrogen reduction on defective SiP.

Main Methods:

• Density Functional Theory (DFT) calculations were employed.
• A defective SiP monolayer (D1-SiP) with a single phosphorus defect was designed.
• Catalytic activity, limiting potential, and reaction pathways for ENRR were simulated.
• Selectivity towards ammonia production and suppression of hydrogen and hydrazine were assessed.

Main Results:

• The D1-SiP monolayer exhibits enhanced electron conductivity and effective N₂ activation.
• A low limiting potential of -0.87 V was achieved via an enzymatic pathway.
• Smooth charge transfer and robust thermal stability were observed.
• D1-SiP demonstrated suppressed side reactions, favoring ammonia synthesis over H₂ and N₂H₄ production.

Conclusions:

• Defective SiP (D1-SiP) is a highly promising metal-free catalyst for ENRR.
• The material's unique electronic and structural properties facilitate efficient and selective ammonia production.
• This study highlights the potential of 2D group IV-V materials for sustainable nitrogen fixation.