TiO₂ protective layers shape photocathode performance in photoelectrochemical CO₂ reduction

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Photoelectrochemical carbon dioxide reduction (PEC CO2R) offers a direct solar-to-chemical conversion pathway.
• Photocathode stability in corrosive PEC environments is crucial for efficient solar fuel production.
• Titanium dioxide (TiO2) is a common protective layer, but its catalytic impact is not well understood.

Purpose of the Study:

• To investigate the role of TiO2 protective layers on Cu2O photocathodes in PEC CO2R.
• To understand how TiO2 influences catalytic selectivity and reaction pathways.
• To establish design principles for effective protective layers in PEC CO2R.

Main Methods:

• Fabrication and characterization of TiO2-protected Cu2O photocathodes with Au, Cu, and Bi cocatalysts.
• Experimental PEC CO2R performance evaluation.
• Computational simulations to analyze interfacial reaction mechanisms.

Main Results:

• TiO2 significantly alters catalytic selectivity, suppressing carbon monoxide (CO) and multicarbon (C2+) formation.
• The impact of TiO2 on formate production selectivity was minimal across different cocatalysts (Bi, In, Sn).
• TiO2 acts as an active component, not an inert stabilizer, by reshaping reaction pathways.

Conclusions:

• TiO2 is not merely a protective layer but actively influences the selectivity of PEC CO2R.
• Understanding TiO2's role is critical for designing efficient and selective photocathodes.
• This study provides key insights for optimizing protective layers in solar chemical conversion systems.