Decoupling Hydrogen Evolution From Continuous Irradiation via CO₂-Mediated Proton-Coupled Electron Storage

Area of Science:

• Materials Science
• Catalysis
• Renewable Energy

Background:

• Solar energy's intermittency and safe hydrogen storage are major hurdles for solar-driven hydrogen production.
• Existing methods struggle to provide continuous hydrogen evolution due to reliance on direct solar irradiation.

Purpose of the Study:

• To develop a system that decouples hydrogen evolution from continuous solar irradiation.
• To address challenges of solar intermittency and safe hydrogen storage in solar-driven hydrogen production.

Main Methods:

• Fabrication of a metal-organic framework/polymeric carbon nitride (MOF/PCN) heterostructure with atomically dispersed copper (Cu) sites.
• Utilizing carbon dioxide (CO2) as a mediator for proton-coupled electron storage.
• Investigating the mechanism through experimental and theoretical analyses.

Main Results:

• The optimized Cu@MOF/PCN-3 heterostructure demonstrated efficient solar energy storage and dark hydrogen production.
• Achieved a hydrogen production rate of 2.88 mmol g⁻¹ in the dark, a 3.2-fold enhancement over control systems.
• CO2 was identified as a bifunctional mediator, stabilizing photoelectrons and facilitating proton transfer via *COOH intermediates.

Conclusions:

• The developed MOF/PCN heterostructure offers a novel CO2-mediated dark photocatalysis approach.
• This method effectively decouples hydrogen evolution from continuous solar irradiation, addressing intermittency.
• The findings present a dual solution for solar intermittency and safe hydrogen storage challenges.