Efficient charge separation and visible-light response in bilayer HfS₂-based van der Waals heterostructures

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) materials like hafnium disulfide (HfS2), hexagonal boron nitride (h-BN), and graphene-like carbon nitride (g-C3N4) are explored for energy applications.
• HfS2 shows potential for photovoltaics, while h-BN and g-C3N4 are investigated for photocatalysis.

Purpose of the Study:

• Investigate HfS2-based van der Waals (vdW) heterojunctions for enhanced photovoltaic and photocatalytic performance.
• Utilize hybrid density functional theory to explore HfS2/h-BN and HfS2/g-C3N4 heterostructures.
• Identify optimal configurations for solar energy conversion and photocatalytic water splitting.

Main Methods:

• Employing hybrid density functional theory (DFT) calculations.
• Synthesizing and fabricating 2D materials including HfS2, h-BN, and g-C3N4.
• Investigating van der Waals (vdW) heterojunctions formed by these materials.

Main Results:

• HfS2/h-BN and HfS2/g-C3N4 heterostructures exhibit type-II semiconductor behavior, facilitating efficient charge separation for photovoltaic applications.
• Tensile strain (6% for HfS2/h-BN, 9% for HfS2/g-C3N4) enhances UV-VIS light absorption and optimizes bandedges for photocatalytic water splitting.
• The HfS2/h-BN heterojunction with 6% strain demonstrates a direct bandgap and complete photoinduced electron-hole pair separation, ideal for visible light photocatalysis.

Conclusions:

• HfS2-based vdW heterojunctions are promising for both photovoltaic and photocatalytic applications.
• The HfS2/h-BN heterojunction, particularly with 6% tensile strain, shows significant potential for efficient visible light photocatalytic water splitting and hydrogen production.
• Strain engineering is a viable strategy to tune the electronic and optical properties of 2D heterostructures for energy conversion.