Protonation-Gated Hydrogen Evolution Enabled by Pyridinic Nitrogen on Graphene Edges

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• High-performance, cost-effective electrocatalysts are crucial for energy conversion technologies.
• Noble metal catalysts are effective but expensive and acid-unstable.
• Metal-free catalysts offer a promising alternative, but require mechanistic understanding and structural control.

Purpose of the Study:

• To design and synthesize novel metal-free electrocatalysts for the hydrogen evolution reaction (HER).
• To investigate the catalytic mechanism of nitrogen-doped graphene edges protected by a ceramic layer.
• To enhance HER activity and stability in acidic environments.

Main Methods:

• Synthesis of ceramic-protected graphene edge electrocatalysts via N2 plasma functionalization.
• In situ electrochemical characterization techniques to study catalytic mechanisms.
• Electrochemical testing to evaluate overpotential and stability over 2000 CV cycles.

Main Results:

• The optimized catalyst demonstrated a low overpotential of 46 mV at 10 mA cm-2 for HER.
• The ceramic protection largely preserved the graphitic framework during functionalization.
• The catalyst exhibited a 6-fold improvement in activity compared to pristine edges and excellent stability.
• A protonation-gated mechanism involving pyridinic nitrogen and adjacent carbon sites was proposed.

Conclusions:

• Ceramic-protected graphene edges represent a highly active and stable metal-free HER electrocatalyst.
• The proposed protonation-gated mechanism provides key mechanistic insights for designing advanced electrocatalysts.
• This approach offers a viable strategy for developing cost-effective alternatives to noble metal catalysts.