A direct Z-scheme NiCo₂O₄/ZnIn₂S₄ heterojunction for highly efficient visible-light-driven H₂ evolution

Area of Science:

• Materials Science
• Photocatalysis
• Renewable Energy

Background:

• Efficient and stable photocatalysts are crucial for hydrogen (H2) production via water splitting.
• Developing advanced materials to enhance photocatalytic activity and stability remains a key challenge.

Purpose of the Study:

• To fabricate a novel sea urchin-like NiCo2O4-decorated ZnIn2S4 heterojunction.
• To investigate the effect of NiCo2O4 decoration on the photocatalytic performance of ZnIn2S4 for H2 production.
• To elucidate the charge transfer mechanism and optimize the composite for enhanced H2 evolution.

Main Methods:

• Solvent evaporation method for fabricating NiCo2O4/ZnIn2S4 heterojunctions.
• UV-vis absorption spectroscopy to assess light absorption properties.
• Electrochemical impedance spectroscopy to study charge transfer resistance.
• ˙OH radical capture experiments to determine the charge transfer pathway.
• Photocatalytic H2 evolution measurements under simulated solar irradiation.

Main Results:

• The NiCo2O4/ZnIn2S4 composite exhibited expanded UV-vis absorption, enhanced light absorption intensity, and improved charge separation.
• The Z-scheme charge transfer route was confirmed, preserving the redox potential of photogenerated carriers.
• The optimized 4.8%-NiCo2O4/ZnIn2S4 composite achieved a H2 evolution rate of 17.28 mmol g-1 h-1, 3.0 times higher than pristine ZnIn2S4.
• The heterojunction demonstrated excellent stability over 5 consecutive photocatalytic cycles.

Conclusions:

• The NiCo2O4 decoration effectively enhances the photocatalytic activity and stability of ZnIn2S4 for H2 production.
• The Z-scheme heterojunction architecture facilitates efficient charge separation and utilization.
• This study presents a promising strategy for designing advanced photocatalysts for solar fuel generation.