Reducing Flavin and Ubiquinone Headgroups with Silicon Nanowire Photocathodes

Area of Science:

• Biohybrid systems
• Artificial photosynthesis
• Electrocatalysis

Background:

• Photosynthetic biohybrids offer a promising route for selective CO2 reduction.
• Studying charge-transfer mechanisms in these systems is complex due to simultaneous processes.
• Model systems are crucial for deconvoluting complex biohybrid functionalities.

Purpose of the Study:

• To investigate the photoelectrochemical reduction of key redox cofactors (ubiquinone-0 and riboflavin) using a simplified biohybrid model system.
• To understand charge-transfer dynamics in biohybrid systems by isolating specific electron-transfer components.
• To evaluate the performance and stability of Pt-decorated silicon nanowires as catalytic architectures.

Main Methods:

• Photoelectrochemical reduction of ubiquinone-0 (UQ0) and riboflavin (Rf) using Pt-decorated n+p-silicon nanowires.
• Utilizing red light (740 nm) irradiation at 100 mW cm-2.
• Measuring onset potentials, Faradaic efficiency (FE), and conversion rates at various potentials (V RHE).
• Conducting long-term stability tests over 12 hours.

Main Results:

• UQ0 was reduced with an onset potential of 0.876 V RHE and achieved a maximum FE of 81% (1.22 μmol cm-2 h-1 at 0.75 V RHE).
• Rf was reduced with an onset potential of 0.691 V RHE and reached a maximum FE of 73% (0.167 μmol cm-2 h-1 at 0.55 V RHE).
• Both UQ0 and Rf demonstrated continuous reduction over a 12-hour period, indicating system robustness.

Conclusions:

• Pt-decorated silicon nanowires are effective for photoelectrochemically reducing UQ0 and Rf, serving as a robust model for biohybrid systems.
• The study successfully deconvoluted charge-transfer processes by employing simplified model systems.
• This work provides insights into optimizing electron transfer for efficient CO2 reduction in artificial photosynthesis.