Nitrite Reduction at Low Overpotentials on N-Doped Carbon: When Metal Single Atoms Become Poisons

Area of Science:

• Catalysis
• Materials Science
• Electrochemistry

Background:

• Carbon materials are often viewed as inert supports in catalysis.
• Understanding the role of carbon supports in metal-catalyzed reactions is crucial for catalyst design.

Purpose of the Study:

• To investigate the catalytic activity of nitrogen-doped carbon (TCNQ900) for nitrite reduction to ammonia.
• To explore the influence of atomically dispersed copper on TCNQ900's catalytic performance.
• To elucidate the reciprocal interactions between metal catalysts and carbon supports.

Main Methods:

• Electrochemical synthesis of nitrogen-doped carbon from tetracyanoquinodimethane (TCNQ900).
• Electrocatalytic testing of TCNQ900 for nitrite reduction to ammonia.
• Investigating the effect of atomically dispersed copper and copper nanoparticles on TCNQ900 catalysis.
• Utilizing molecular analogues to confirm catalytic mechanisms.

Main Results:

• TCNQ900 alone catalyzes nitrite reduction to ammonia with high activity and a favorable onset potential.
• Atomically dispersed copper on TCNQ900 inhibits nitrite reduction by blocking active nitrogen sites.
• Physically mixing copper nanoparticles with TCNQ900 creates a tandem catalyst that enhances nitrate reduction to ammonia by fourfold.
• Demonstrated the active role of nitrogen-rich motifs in TCNQ900 for nitrite reduction.

Conclusions:

• Nitrogen-doped carbon supports can be active catalysts, not just passive modulators.
• The interaction between metals and carbon supports is reciprocal, influencing catalytic outcomes.
• This work provides new design principles for metal-carbon electrocatalysts, highlighting the importance of avoiding site poisoning.