Ferroelectric Modulation of Surface Electronic States in BaTiO₃ for Enhanced Hydrogen Evolution Activity

Area of Science:

• Materials Science
• Surface Science
• Electrochemistry

Background:

• Ferroelectric nanomaterials show potential for switchable surface electronic properties applicable to catalysis.
• Previous studies on ferroelectric surfaces in electrocatalysis primarily used nanoparticle systems, leading to complex interfaces.

Purpose of the Study:

• To investigate the impact of ferroelectric polarization on electronic structure and electrochemical activity for the hydrogen evolution reaction (HER).
• To utilize well-defined epitaxial barium titanate (BaTiO3) thin films as model systems to overcome complexities of nanoparticle interfaces.

Main Methods:

• Epitaxial growth of BaTiO3 thin films using Molecular Beam Epitaxy (MBE).
• Surface spectroscopy and *ab initio* Density Functional Theory with Hubbard U (DFT+U) calculations on (001) surfaces.
• Experimental electrochemical measurements of the hydrogen evolution reaction (HER).

Main Results:

• Upward polarized BaTiO3 surfaces exhibit a reduced work function compared to downward polarized surfaces.
• A smaller HER activation energy barrier was observed for upward polarized surfaces.
• Experimental results showed higher electrocatalytic activity for upward polarized surfaces, consistent with theoretical predictions.

Conclusions:

• Ferroelectric polarization in BaTiO3 thin films significantly influences surface electronic structure and HER activity.
• The study demonstrates the potential of using ferroelectric polarization to engineer electrocatalytic surfaces.
• This approach offers new avenues for designing nanoscale catalysts by controlling adsorbate interactions.