Coordination-Engineered Carboxylated MN₄-Macrocycles With Chloride-Modulated Proton Hopping for Efficient Hydrogen...

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Developing efficient and stable catalysts for the hydrogen evolution reaction (HER) is crucial for clean energy technologies.
• Existing catalysts often struggle with stability and performance in acidic and chloride-containing electrolytes, limiting their practical application.
• Coordination engineering of π-conjugated frameworks offers a promising strategy for designing advanced catalytic materials.

Purpose of the Study:

• To design and synthesize molecularly versatile, acid-stable, and chloride-tolerant catalysts for electrochemical hydrogen evolution.
• To elucidate the roles of coordination environment, electronic delocalization, and electrolyte composition in HER performance.
• To explore a molecular-electrolyte co-design approach for optimizing hydrogen evolution catalysts.

Main Methods:

• Synthesis of carboxyl-functionalized metal (Ni⁺²/Co⁺²) phthalocyanines in monomeric and polymeric forms.
• Electrochemical characterization of catalysts for hydrogen evolution reaction (HER) in various acidic and chloride-containing electrolytes.
• Post-stability characterization to assess catalyst integrity and performance over time.

Main Results:

• Polymeric nickel phthalocyanine (poly-[CNiPc]) exhibited the lowest overpotential (-76 mV at -10 mA cm^-2) and an excellent Tafel slope (38 mV dec^-1) in 0.5 M H₂SO₄.
• Optimal HER performance was achieved with 0.1 M NaCl in 0.5 M H₂SO₄, yielding an overpotential of -55 mV.
• Catalyst maintained Ni²⁺-N₄ coordination after 60 hours of operation, demonstrating significant stability.

Conclusions:

• The study demonstrates a successful molecular-electrolyte co-design strategy for developing robust hydrogen evolution catalysts.
• Halide-regulated proton transport and π-conjugated phthalocyanine frameworks synergistically enhance HER activity in challenging media.
• The designed catalysts offer a versatile and stable pathway for efficient hydrogen production in acidic and chloride-tolerant environments.