In situ surface-enhanced infrared absorption analysis of the excited carrier transfer from n-type Si photoelectrode to Pt oxygen evolution cocatalyst by probing adsorbed CO molecules

Background: The development of efficient photoelectrode material for water-splitting reactions has received considerable attention as it produces hydrogen gas from water using solar energy. Photoexcited holes migrate to the surface of an n-type photoelectrode oxidizing water to oxygen, and excited electrons migrate to the counter electrode reducing protons to hydrogen. However, there is limited knowledge of excited carrier transfer. Methods: Therefore, in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) has been used to investigate the excited hole migration from n-type Si photoelectrode to Pt oxygen evolution cocatalysts by monitoring the frequency of CO adsorbed on the Pt cocatalysts. Significant findings: At the positive potential of Si photoelectrode under UV irradiation, the SEIRA spectrum of the CO adsorbed on the Pt cocatalyst shifted to higher wavenumbers owing to the excited hole transfer from n-type Si photoelectrode to the Pt cocatalyst attributed to band bending at the interface between the Si photoelectrode and Pt cocatalysts. It was successfully demonstrated that the regulation of photoexcited carriers was crucial for enhancing the photoelectrochemical activity of water splitting.