Modulating Interfacial Charge Dynamics and O₂ Activation over Defective SrTiO₃ via Cation Engineering: Insights from...

Area of Science:

• Materials Science
• Environmental Chemistry
• Catalysis

Background:

• Pharmaceutical residues in wastewater pose health risks, necessitating sustainable remediation technologies.
• Current methods are often energy-intensive, highlighting the need for efficient alternatives like photocatalysis.
• Semiconductor photocatalysis shows promise but is limited by challenges in band gap tuning and catalytic efficiency.

Purpose of the Study:

• To develop a green and precise cation-engineering strategy for fabricating defect-rich perovskite strontium titanate (SrTiO3) photocatalysts.
• To investigate the influence of alkali metal cations on microstructure and defect density for enhanced photocatalytic activity.
• To elucidate the mechanisms behind improved pharmaceutical degradation using theoretical and experimental approaches.

Main Methods:

• Fabrication of SrTiO3 photocatalysts using a molten-salt-like hydrothermal process with alkali nitrates (LiNO3, NaNO3, KNO3).
• Characterization of material properties, including microstructure, defect density (oxygen vacancies, Ti3+), and electronic band structure.
• Photocatalytic degradation experiments for tetracycline and ibuprofen under visible light, coupled with DFT simulations and radical trapping studies.

Main Results:

• Potassium ion (K+) induction resulted in flower-like hierarchical SrTiO3 spheres with high concentrations of oxygen vacancies and Ti3+ species.
• Defect-rich SrTiO3 exhibited enhanced band structure, interfacial properties, and carrier efficiency, leading to significantly faster degradation rates (2.25x for tetracycline, 2.12x for ibuprofen) and higher turnover frequency (3.8x).
• DFT simulations confirmed that vacancy-induced O2 activation, improved carrier dynamics (4.93 ns lifetime, 5.7x photocurrent), and enhanced molecule adsorption were key to the superior performance.

Conclusions:

• A versatile cation-specific defect engineering strategy was established for designing high-performance perovskite photocatalysts.
• The optimized defective SrTiO3 microstructure and stable surface defects are crucial for efficient pharmaceutical degradation.
• This approach provides fundamental insights into modulating charge dynamics and reaction pathways for advanced water treatment applications.