Selective Nitrate Electroreduction to Ammonia on CNT Electrodes with Controllable Interfacial Wettability

Area of Science:

• Electrochemistry
• Materials Science
• Environmental Science

Background:

• Electrocatalytic nitrate reduction to ammonia offers a sustainable route for nitrogen management and chemical synthesis.
• Optimizing the catalyst's microenvironment is critical for improving selectivity and efficiency.
• Understanding interfacial properties is key to designing high-performance electrocatalysts.

Purpose of the Study:

• To investigate the impact of interfacial wettability on nitrate reduction to ammonia.
• To explore the use of quaternary ammonium surfactants for modifying carbon nanotube electrodes.
• To enhance ammonia selectivity and understand the underlying reaction mechanisms.

Main Methods:

• Electrochemical modification of carbon nanotubes (CNTs) using quaternary ammonium surfactants.
• Tuning interfacial wettability through varying surfactant alkyl chain lengths.
• Operando Fourier-transform infrared (FTIR) spectroscopy and online differential electrochemical mass spectrometry (DEMS) for mechanistic studies.

Main Results:

• A hydrophobic interface, achieved with trimethyltetradecylammonium bromide, resulted in high ammonia selectivity (∼87%).
• The hydrophobic surface effectively suppressed competing hydrogen evolution reactions.
• A direct electron transfer pathway was favored for nitrate reduction to ammonia.

Conclusions:

• Controlling the hydrophobic surface of electrocatalysts is a significant strategy for enhancing electrochemical performance in aqueous media.
• Surfactant-modified CNTs provide a promising platform for efficient and selective nitrate-to-ammonia conversion.
• The study highlights the importance of microenvironment engineering in electrocatalysis.