Biomimetic Dual-Iron-Site Single-Atom Nanozymes for N₂-Selective Electrocatalytic Denitrification

Area of Science:

• Environmental Science
• Catalysis
• Materials Science

Background:

• Electrocatalytic denitrification (ECDN) is a promising method for removing nitrate from wastewater.
• Current ECDN methods face challenges with low nitrogen gas (N$_{2}$) selectivity.
• Mimicking natural enzymes offers a pathway to improved electrocatalyst performance.

Purpose of the Study:

• To develop a novel electrocatalyst for highly selective ECDN.
• To investigate the mechanism of N$_{2}$ formation during ECDN.
• To demonstrate the application of the electrocatalyst in treating realistic wastewater.

Main Methods:

• Synthesis of a dual-iron-site single-atom nanozyme (FePc@FeNOC) electrocatalyst.
• Electrocatalytic performance evaluation for nitrate reduction.
• Density functional theory (DFT) calculations to elucidate reaction mechanisms.
• Testing in realistic photovoltaic wastewater.

Main Results:

• FePc@FeNOC achieved 96.1% nitrate removal efficiency with 93.3% N$_{2}$ selectivity.
• DFT calculations revealed a lower energy barrier for N$_{2}$ formation compared to ammonia (NH$_{3}$).
• The electrocatalyst demonstrated superior performance in realistic wastewater with low energy consumption (9.8 kWh kgN$_{2}$$^{-1}$).

Conclusions:

• The FePc@FeNOC electrocatalyst effectively mimics cytochrome c-dependent nitric oxide reductase (cNOR) for selective ECDN.
• The catalyst's design promotes favorable N$_{2}$ formation pathways.
• This work presents a sustainable and efficient approach for nitrate removal from contaminated wastewater.