Synergistic Fluorine Doping and Oxygen Vacancy Formation in Hematite Photoanodes via Solid-State Thermite Defect...

Area of Science:

• Materials Science
• Electrochemistry
• Surface Chemistry

Background:

• Defect engineering is vital for improving metal oxide photoanode performance.
• Conventional fluorine doping methods for hematite (α-Fe2O3) cause detrimental surface etching.
• Developing efficient and non-destructive doping strategies is crucial for photoanode applications.

Purpose of the Study:

• To develop a novel, solvent-free defect engineering strategy for hematite photoanodes.
• To simultaneously introduce fluorine doping and oxygen vacancies into hematite.
• To enhance the photoelectrochemical performance of hematite by overcoming charge transfer limitations.

Main Methods:

• A solid-state thermite reaction using fluororubber-coated aluminum (Al@F2311) was employed.
• Heating the Al@F2311 composite to 400 °C induced a localized thermite reaction.
• This reaction facilitated fluorine substitution and oxygen vacancy creation in the near-surface region of hematite.

Main Results:

• The resulting dual-defect Hem-AlF photoanode exhibited a 5.65-fold enhancement in photocurrent density (1.13 mA cm⁻² at 1.23 V vs RHE) compared to pristine hematite.
• The enhancement is attributed to increased donor density, reduced interfacial charge transfer resistance, and improved surface hydrophilicity (contact angle of 49.7°).
• The method successfully avoided bulk structure disruption and severe surface etching.

Conclusions:

• The solid-state thermite defect engineering approach offers an effective and scalable method for F-doping and creating oxygen vacancies in hematite.
• This solvent-free paradigm integrates energetic material kinetics into semiconductor defect engineering, paving the way for advanced photoanode design.
• The dual-defect strategy significantly boosts photoelectrochemical performance, addressing key limitations in current technologies.