Interfacial d-Band Center Modulation via Si-Ir Coupling Enables Efficient and Durable Acidic Solar Water Splitting

Area of Science:

• Materials Science
• Electrochemistry
• Photocatalysis

Background:

• Photoelectrochemical (PEC) water oxidation in acidic media faces challenges from photo-corrosion and slow reaction rates.
• Hematite (α-Fe2O3) is a promising photoanode material but suffers from instability and inefficiency in acidic conditions.

Purpose of the Study:

• To develop a novel dual-modification strategy for hematite photoanodes to improve efficiency and stability in acidic PEC water oxidation.
• To investigate the synergistic effects of silicon oxide passivation and iridium oxide cocatalysis on hematite performance.

Main Methods:

• Fabrication of dual-modified hematite photoanodes with silicon oxide (SiO_x) and iridium oxide (IrO_x).
• Electrochemical and photoelectrochemical characterization in acidic electrolyte.
• Surface passivation and cocatalyst integration analysis.
• Density Functional Theory (DFT) calculations to understand interfacial electronic interactions.

Main Results:

• The optimized Fe2O3-Si/Ir photoanode achieved a record photocurrent density of 2.32 mA cm⁻² at 1.23 V_RHE.
• Exceptional stability was demonstrated, with the photoanode operating effectively for over 60 minutes in acidic conditions.
• The SiO_x layer effectively passivated surface states, promoted uniform IrO_x network formation, and prevented iridium over-oxidation.
• Evidence of strong electronic interaction at the Si-Ir interface, enhancing charge transfer and reducing activation energy for water oxidation.

Conclusions:

• The dual-modification approach with SiO_x and IrO_x provides a synergistic strategy for highly efficient and durable hematite-based PEC water oxidation in acidic media.
• This work offers a viable pathway for practical solar hydrogen production through improved photoanode design.
• The multifunctional role of SiO_x is crucial for overcoming limitations in hematite PEC performance.