The quantum size and spin-orbit coupling effects in BiVO₄ with several atomic layers studied by density functional...

Area of Science:

• Materials Science
• Quantum Mechanics
• Photocatalysis

Background:

• Quantum size and spin-orbit coupling (SOC) effects influence electronic structures in photocatalysts containing heavy elements.
• Understanding their impact on conduction band (CB) and valence band (VB) edges is crucial but not well-established.
• Bismuth vanadate (BiVO4) is a known water oxidation catalyst lacking hydrogen reduction capabilities.

Purpose of the Study:

• Investigate quantum size and SOC effects on the CB and VB edges of few-layer BiVO4.
• Determine how these effects influence the photocatalytic activity, particularly for hydrogen evolution.
• Provide insights for rational photocatalyst design.

Main Methods:

• Theoretical investigation of quantum size and SOC effects.
• Analysis of BiVO4 layers with varying atomic thicknesses.
• Comparison of CB and VB edge positions relative to redox potentials.

Main Results:

• Quantum size effect upshifts the CB edge in BiVO4 layers < 0.64 nm.
• SOC effect has minimal impact on the CB edge in these thin layers.
• BiVO4 CB edge exceeds H2/H2O redox potentials at thicknesses of ~0.64–1.28 nm due to quantum size effects.
• Both quantum size and SOC effects are negligible for BiVO4 layers > 1.28 nm.

Conclusions:

• Quantum size effects are dominant in thin BiVO4 layers, enhancing CB edge potential.
• SOC effects play a minor role in the studied thickness range.
• Thickness control is critical for tuning BiVO4 photocatalytic properties.
• Findings advance the understanding and design of effective photocatalysts.