Organic Semiconductor-BiVO₄ Tandem Devices for Solar-Driven H₂O and CO₂ Splitting

Area of Science:

• Materials Science
• Renewable Energy
• Electrochemistry

Background:

• Photoelectrochemical (PEC) devices are key for solar energy conversion and chemical storage via artificial photosynthesis.
• Existing PEC prototypes often use unstable materials like wide bandgap semiconductors or sensitive inorganic light absorbers, limiting their practical application.
• The use of corrosive electrolytes in many PEC systems hinders their long-term stability and environmental compatibility.

Purpose of the Study:

• To design and assemble robust PEC devices utilizing organic donor-acceptor bulk heterojunction (BHJ) materials.
• To demonstrate long-term solar-driven hydrogen evolution and carbon dioxide reduction in environmentally benign aqueous solutions.
• To develop efficient tandem PEC devices for simultaneous syngas production and oxygen evolution.

Main Methods:

• Fabrication of PEC devices with an organic donor-acceptor bulk heterojunction (BHJ) active layer.
• Encapsulation of the organic BHJ using a carbon-based material for enhanced stability.
• Testing of photocathodes for hydrogen evolution and carbon dioxide reduction in near-neutral pH aqueous media.
• Assembly and testing of tandem PEC devices (artificial leaves) for syngas production.

Main Results:

• PCE10:EH-IDTBR photocathodes demonstrated sustained hydrogen production for over 300 hours in near-neutral pH solution.
• Photocathodes integrated with a molecular CO2 reduction catalyst achieved a CO:H2 selectivity of 5.41±0.53 under 0.1 sun irradiation.
• Tandem PEC devices comprising PCE10:EH-IDTBR and BiVO4 efficiently produced syngas (CO and H2) with a 1:1 ratio for 96 hours, powered solely by sunlight.

Conclusions:

• The developed organic BHJ-based PEC devices offer a stable and efficient platform for artificial photosynthesis in aqueous media.
• These devices overcome limitations of traditional PEC systems, paving the way for practical solar fuel production.
• The successful demonstration of tandem artificial leaves highlights the potential for unassisted solar-driven syngas generation and oxygen evolution.