Understanding potential-dependent competition between electrocatalytic dinitrogen and proton reduction reactions.

Area of Science:

• Electrochemistry
• Catalysis
• Materials Science

Background:

• Achieving efficient electrochemical nitrogen reduction reaction (NRR) is hindered by activity loss before mass-transfer limitations.
• The role of hydrogen evolution reaction (HER) in suppressing NRR is suspected but mechanistically unclear.

Purpose of the Study:

• To elucidate the potential-dependent competition between NRR and HER.
• To identify the mechanistic origin of premature NRR activity decline.

Main Methods:

• Utilized constant electrode potential modeling.
• Employed microkinetic modeling to analyze reaction pathways.

Main Results:

• Discovered a crossover in hydrogen (H) and nitrogen (N2) coverage.
• Linked this coverage crossover to a premature decrease in NRR activity.
• Identified larger charge transfer in H+ adsorption compared to N2 adsorption as the cause.

Conclusions:

• The H and N2 coverage crossover, driven by differential charge transfer, poses a fundamental challenge for electrochemical NRR.
• Strategies to overcome this challenge can be developed based on understanding catalyst surface interactions.