Pulsed Electrocatalysis Enabling High Overall Nitrogen Fixation Performance for Atomically Dispersed Fe on TiO₂

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Developing efficient electrocatalysts for nitrogen fixation is crucial for sustainable ammonia production and nitrogen cycle management.
• Single-atom catalysts offer unique electronic properties for enhanced catalytic activity.
• The nitrogen oxidation reaction (NOR) and nitrogen reduction reaction (NRR) are key processes in nitrogen electrochemistry.

Purpose of the Study:

• To design and investigate atomically dispersed Fe on TiO2 as a bifunctional electrocatalyst for both NOR and NRR.
• To explore the application of pulsed electrochemical catalysis (PE) for inhibiting competing reactions like hydrogen evolution reaction (HER) and oxygen evolution reaction (OER).
• To understand the mechanism behind the enhanced N2 fixation performance using experimental and theoretical calculations.

Main Methods:

• Synthesis of atomically dispersed Fe on TiO2.
• Electrochemical characterization in a two-electrode system.
• Application of pulsed electrochemical catalysis (PE) and constant voltage electrocatalysis.
• Density Functional Theory (DFT) calculations.

Main Results:

• Achieved high yields for NOR (7055.81 μmol h⁻¹ g⁻¹ cat.) and NRR (12868.33 μmol h⁻¹ g⁻¹ cat.) at 3.5 V.
• Observed significant increases in Faradaic efficiency (FE) for NOR (44.94 times) and NRR (7.8 times) compared to conventional methods.
• DFT calculations indicated Fe stabilizes oxygen vacancies and lowers the N≡N bond dissociation barrier.
• PE effectively enhanced N2 supply and suppressed byproduct formation.

Conclusions:

• Atomically dispersed Fe/TiO2 acts as an effective Janus electrocatalyst for both NOR and NRR.
• Pulsed electrochemical catalysis is a promising strategy to improve N2 fixation efficiency by managing competing reactions and intermediates.
• The synergistic effect between single-atom Fe and TiO2, coupled with PE, leads to superior N2 electrocatalytic performance.