Charge generation dynamics in hematite photoanodes decorated with gold nanostructures under near infrared excitation.

Photochemical water splitting offers a useful solution for efficient energy conversion into hydrogen gas. Hematite has been focused on this purpose as the photoanode due to the advantages of low-cost, chemical stability, and suitable bandgap. The photocatalytic ability, however, is limited by the short-lived carriers and lack of photoresponse in the near infrared (NIR) region. As a solution, combining hematite with a noble metal can enhance the photocatalytic performance toward longer wavelength. Gold nanoparticles indicate characteristic absorption in the visible and NIR regions and photo-induced injection of electrons into the semiconductor. In this study, a hybrid material of hematite photoanodes with gold nanostructures was fabricated and the carrier dynamics under NIR excitation was elucidated by femtosecond transient absorption spectroscopy. The observed strong positive absorption under NIR excitation of Au nanorods (NRs) on the hematite anode indicated an increased electron density in hematite due to electron transfer from AuNRs, demonstrating efficient charge carrier generation in hematite by the decorated gold nanostructure.