Strong Enhancement in Cobalt(II)-TPMA Aqueous Hydrogen Photosynthesis through Intramolecular Proton Relay

Area of Science:

• Inorganic Chemistry
• Photocatalysis
• Renewable Energy

Background:

• Photosynthetic hydrogen generation using cobalt complexes is hindered by slow protonation and catalyst decomposition.
• Cobalt(II) tris(2-pyridylmethyl)amine (TPMA) complexes show promise but require optimization for efficient solar fuel production.

Purpose of the Study:

• To investigate the impact of proton shuttles and structural rigidity on cobalt(II) TPMA complex catalytic performance.
• To enhance hydrogen generation efficiency and catalyst stability through molecular design.

Main Methods:

• Synthesis and characterization of modified cobalt(II) TPMA complexes.
• Evaluation of catalytic activity for hydrogen evolution.
• Transient absorption spectroscopy to study proton transfer mechanisms.

Main Results:

• A rigid cage structure offered minor catalytic improvement.
• Ammonium groups as proton relays increased quantum efficiency 4-fold and maximum turnover number 22-fold.
• Spectroscopic evidence confirmed faster intramolecular proton transfer facilitated by ammonium relays.

Conclusions:

• Tuning the periphery of cobalt catalysts with proton relays is crucial for efficient solar fuel generation.
• Optimized cobalt(II) TPMA complexes demonstrate significant potential for improved hydrogen production.
• This work highlights a viable strategy for advancing photocatalytic hydrogen evolution.