Unassisted Switchable Dual-Photoelectrode Devices Utilizing p-n Carbon Quantum Dots as "Semiconductor Electrolytes":...

Area of Science:

• Materials Science
• Electrochemistry
• Photochemistry

Background:

• Photoelectrochemical (PEC) devices offer sustainable routes for energy conversion and chemical production.
• Traditional electrolytes in PEC devices often face limitations in charge separation, selectivity, and long-term stability.
• Developing novel electrolyte materials is crucial for advancing PEC device performance.

Purpose of the Study:

• To introduce nitrogen-doped carbon quantum dots (N-CQDs) as semiconductor electrolytes in switchable PEC devices.
• To demonstrate the dual functionality of N-CQDs in facilitating either hydrogen peroxide (H₂O₂) or electricity generation.
• To investigate the enhanced charge separation, selectivity, and durability enabled by N-CQDs.

Main Methods:

• Fabrication of p-n type N-CQDs with charged surface groups.
• Integration of N-CQDs as electrolytes in two-compartment and one-compartment PEC cells with BiVO₄ photoanode and Cu₂O photocathode.
• Characterization of N-CQDs' electronic structure and their interaction with photoelectrodes.
• Evaluation of H₂O₂ production rate and Faradaic efficiency.
• Assessment of electricity generation stability over extended periods.

Main Results:

• N-CQDs successfully acted as semiconductor electrolytes, interacting with both photoanode and photocathode.
• In a two-compartment cell, N-CQDs formed dynamic p-n heterojunctions, achieving H₂O₂ production at 28 µm min^-1 with >80% Faradaic efficiency.
• In a one-compartment cell, N-CQDs promoted four-electron transfer and stabilized photoelectrodes for over 120 h of electricity generation.
• The N-CQDs demonstrated superior control over electron transfer, selectivity, and durability compared to conventional electrolytes.

Conclusions:

• N-CQDs represent a conceptually new class of semiconductor electrolytes for PEC applications.
• Switchable PEC devices utilizing N-CQDs offer tunable performance for targeted H₂O₂ or electricity generation.
• The unique properties of N-CQDs overcome limitations of traditional electrolytes, paving the way for more efficient and durable PEC systems.