Morphology-controlled Cu₂SnS₃ quantum dot-sensitized solar PEC cells for efficient hydrogen production

Area of Science:

• Materials Science
• Renewable Energy
• Nanotechnology

Background:

• Quantum dot (QD) morphology and size regularity critically impact solar photoelectrochemical (PEC) cell performance.
• Developing efficient and stable PEC cells for solar-to-hydrogen conversion is crucial for renewable energy.
• Copper tin sulfide (CTS) quantum dots offer potential as green photosensitizers for PEC applications.

Purpose of the Study:

• To synthesize and compare sphere-like and bullet-like green CTS quantum dots.
• To fabricate and evaluate p-n heterojunction photoanodes using these CTS QDs for solar water splitting.
• To investigate the influence of QD morphology on PEC performance and hydrogen production.

Main Methods:

• Hot injection synthesis of sphere-like and bullet-like CTS QDs by modulating sulfur precursor ratios.
• Deposition of CTS QDs onto TiO2 nanorod arrays to form p-n heterojunction photoanodes.
• Assembly of photoanodes into PEC cells with Pt counter electrodes for hydrogen production measurements under simulated solar illumination (AM 1.5G).

Main Results:

• Sphere-like CTS QDs exhibited a more negative conduction-band minimum and narrower bandgap than bullet-like QDs, enhancing light absorption.
• The sphere-like CTS/TiO2 photoanode achieved a photocurrent density of 2.54 mA cm-2 and a hydrogen production yield of 162.1 μmol cm-2 within 4 hours.
• Exceptional long-term stability was demonstrated, with sustained hydrogen production for 16 consecutive hours.

Conclusions:

• The systematic spherical structure and homogeneous size distribution of sphere-like CTS QDs significantly enhance PEC performance.
• Improved photoabsorption, shorter charge-carrier diffusion lengths, and efficient charge separation contribute to the enhanced performance.
• Modulating QD morphology and size uniformity presents a viable strategy for boosting light-harvesting and charge separation in PEC systems for efficient solar-to-hydrogen conversion.