Solar Hydrogen Generation from Ambient Humidity Using Functionalized Porous Photoanodes

Area of Science:

• Materials Science
• Renewable Energy
• Electrochemistry

Background:

• Solar hydrogen production via photoelectrochemical (PEC) cells is a key sustainable energy goal.
• Conventional PEC systems using liquid electrolytes face limitations like light scattering and mass transport issues.
• Utilizing ambient water vapor as a feedstock offers a promising alternative to overcome these challenges.

Purpose of the Study:

• To develop and optimize photoanodes capable of capturing atmospheric water vapor for PEC hydrogen production.
• To investigate the impact of ionomer functionalization on photoanode performance using ambient humidity.
• To assess the stability and efficiency of these devices under varying conditions.

Main Methods:

• Functionalization of porous titanium dioxide (TiO2) and tungsten trioxide (WO3) photoanodes with proton-conducting ionomers (Aquivion and Nafion).
• Optimization of ionomer loading and composition for enhanced water vapor capture and PEC performance.
• Testing of functionalized photoanodes under controlled humidity (60% RH) and temperature (30-70 °C) conditions.
• Long-term stability testing involving cycling between illumination and dark periods.

Main Results:

• Optimized functionalized photoanodes recovered up to 90% of liquid-phase performance at 60% RH and 30-70 °C.
• Full performance recovery was achieved at higher applied potentials.
• Demonstrated remarkable stability over 64 hours of cycling under 60% RH, indicating outdoor applicability.

Conclusions:

• Functionalization with solid electrolytes enables efficient water vapor capture from ambient air for PEC hydrogen production.
• This approach mitigates issues associated with liquid electrolytes and expands the operational range of PEC devices.
• The developed technology shows significant potential for sustainable, outdoor hydrogen generation.