Electronic structure investigation of Ta- and Nb-doped hematite nanorod arrays for photoelectrochemical water splitting
W.Y.Lee1,4*, J.L.Chen4, Y.Fu2, S.H.Shen2, Y.C.Hung1,4, Y.X.Chen1,4, Y.R.Lu1,4, W.C.Chou3, C.L.Dong5
1Program for Science and Technology of Accelerator Light Source, National Chiao Tung University, Hsinchu, Taiwan
2International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an, China
3Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan
4National Synchrotron Radiation Research Center (NSRRC), Hsinchu, Taiwan
5Department of Physics, Tamkang University, New Taipei City, Taiwan
* presenting author:Wan-Yi Lee, email:cindy800829@gmail.com
Photoelectrochemical (PEC) water splitting is an attractive approach converting sun light to hydrogen, which is one of the most important renewable energies. Owing to the narrow band gap (about 2.1 eV), abundance, low cost, and high chemical stability, hematite (α-Fe2O3) has been considered as a promising candidates for the pivotal component of a PEC photoanode. However, the conduction band is lower than hydrogen evolution potential. Nanostructuring/doping is a way to imporve the photocatalytic performance of α-Fe2O3 film. The PEC performances of doped α-Fe2O3 film depend strongly on the dopant concentraions. With increasing the doping level, the performance is improved. However, with superflous dopants, the nanorods film exhibits decreased PEC performance. In this study, in situ x-ray absorption spectroscopy (XAS) was used to investigate the electronic structures of hematite nanorods with different doping (Nb and Ta). The resutls reveal that compared with bare α-Fe2O3 nanorods film, the doped film varies the density of unoccupied states and enhances charge transfer ability, which are believed to be the main consequence for the better PEC performance.

Keywords: X-ray Absorption Spectroscopy, Photoelectrochemical, Water Splitting, Hematite