Calcium-mediated nitrogen reduction for electrochemical ammonia synthesis

Area of Science:

• Electrochemistry
• Materials Science
• Chemical Engineering

Background:

• Ammonia (NH3) is crucial for agriculture, textiles, and pharmaceuticals but is primarily produced via the carbon-intensive Haber-Bosch process.
• Electrochemical methods offer a decentralized, renewable alternative for ammonia synthesis, but exploration beyond lithium mediators is limited.
• Current lithium-mediated processes face challenges in efficiency, scalability, and material abundance.

Purpose of the Study:

• To investigate the potential of alternative elements to lithium for mediating electrochemical ammonia synthesis.
• To demonstrate a viable, lithium-free electrochemical pathway for ammonia production.
• To assess the efficiency and feasibility of using calcium as a mediator.

Main Methods:

• Developed and tested a novel electrochemical system for nitrogen reduction to ammonia.
• Utilized calcium tetrakis(hexafluoroisopropyloxy)borate (Ca[B(hfip)4]2) as the electrolyte in an organic medium.
• Employed a rigorous verification protocol to quantify ammonia yield and Faradaic efficiency.

Main Results:

• Successfully demonstrated a calcium-mediated electrochemical process for ammonia synthesis.
• Achieved a significant ammonia Faradaic efficiency of 40 ± 2%.
• Validated the use of calcium as an effective mediator, offering a lithium-free alternative.

Conclusions:

• Calcium can effectively mediate the electrochemical reduction of nitrogen to ammonia.
• This calcium-based system presents a promising, sustainable, and potentially more abundant alternative to existing ammonia production methods.
• The findings open avenues for decentralized, renewable ammonia synthesis using earth-abundant materials.