Abstract
Hematite (α-Fe2O3) has been extensively studied as a promising candidate for photoelectrochemical water splitting; however its overall efficiency is still relatively low. Doping is believed to be efficient in enhancing the photoactivity, while direct evidence for the promoted charge carrier dynamics is very limited. Herein, transient absorption spectroscopy was used to directly investigate the yield and decay dynamics of the photogenerated holes in Sn and/or Ti doped α-Fe2O3. Sn or Ti doping was observed to have different origins to the enhanced water oxidation photocurrent: Sn doping retarded the electron-hole recombination, while Ti doping mainly increased the photogenerated charge carrier density. Our results also demonstrated that co-doping may combine both advantages to enhance the overall photoactivity of α-Fe2O3.
Highlights
Transient absorption spectroscopy (TAS) can directly monitor the dynamics of photogenerated charge carriers.[24] During the past few years, the dynamics of photogenerated charge carriers in hematite with and without surface modification were intensively studied by Durrant’s group,[25,26,27,28,29,30,31,32,33] mainly on a time scale of ms–s, which demonstrated that photocurrents were related to photogenerated long-lived holes,[27] and surface modification formed a hetero-conjunction at the surface of hematite films,[28,29,30] instead of recombining with photogenerated electrons, 9806 | Phys
Hydrogen production from solar-driven water splitting has been regarded as one of the most promising routes to address the increasing energy and environmental issues our society is facing
We have investigated the charge carrier dynamics in hematite before and after Sn and/or Ti doping
Summary
Transient absorption spectroscopy (TAS) can directly monitor the dynamics of photogenerated charge carriers.[24] During the past few years, the dynamics of photogenerated charge carriers in hematite with and without surface modification were intensively studied by Durrant’s group,[25,26,27,28,29,30,31,32,33] mainly on a time scale of ms–s, which demonstrated that photocurrents were related to photogenerated long-lived holes,[27] and surface modification formed a hetero-conjunction at the surface of hematite films,[28,29,30] instead of recombining with photogenerated electrons, 9806 | Phys. Consistent with most of the reported observations,[8,9,11,12] with increasing applied bias, either Sn or Ti doping resulted in significant enhancement of the water oxidation photocurrent by more than one-fold (Fig. S3a, ESI†), though compared with pristine hematite the nanostructure of the doped samples should be changed using the surface doping method.[16] We note that, Sn and Ti co-doped hematite further increased the photocurrent compared with either Sn or Ti doping.
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