3 research outputs found
Intrinsic photoanode band engineering: enhanced solar water splitting efficiency mediated by surface segregation in Ti-doped hematite nanorods
Band engineering is thoroughly employed nowadays targeting technologically
scalable photoanodes for solar water splitting applications. Most often complex
and costly recipes are necessary, for average performances. Here we report very
simple photoanode growth and thermal annealing, with effective band engineering
results. Strongly enhanced photocurrent, of more than 200 %, is measured for
Ti-doped hematite nanorods grown from aqueous solutions and annealed under
Nitrogen atmosphere, compared to air annealed ones. Oxidized surface states and
increased density of charge carriers are found responsible for the enhanced
photoelectrochemical activity, as shown by electrochemical impedance
spectroscopy and synchrotron X-rays spectromicroscopies. They are found related
to oxygen vacancies, acting as n-dopants, and the formation of pseudo- brookite
clusters by surface Ti segregation. Spectro-ptychography is used for the first
time at Ti L3 absorption edge to isolate Ti chemical coordination arising from
pseudo-brookite clusters contribution. Correlated with electron microscopy
investigation and Density Functional Theory (DFT) calculations, our data
unambiguously prove the origin of the enhanced photoelectrochemical activity of
N2-annealed Ti-doped hematite nanorods. Finally, we present here a handy and
cheap surface engineering method beyond the known oxygen vacancy doping,
allowing a net gain in the photoelectrochemical activity for the hematite-based
photoanodes.Comment: 2 parts: first main manuscript with 39 pages, second supplementary
informations with 14 page
Enhancement of the Solar Water Splitting Efficiency Mediated by Surface Segregation in Ti-Doped Hematite Nanorods
International audienc
Enhancement of the Solar Water Splitting Efficiency Mediated by Surface Segregation in Ti-doped Hematite Nanorods
Band engineering is employed thoroughly and targets technologically scalable photoanodes for solar water splitting applications. Complex and costly recipes are necessary, often for average performances. Here we report simple photoanode growth and thermal annealing, with effective band engineering results. By comparing Ti-doped hematite photoanodes annealed under Nitrogen to photoanodes annealed in air, we found strongly enhanced photocurrent, of more than 200 % in the first case. Using electrochemical impedance spectroscopy and synchrotron X-rays spectromicroscopies we demonstrate that oxidized surface states and increased density of charge carriers are responsible for the enhanced photoelectrochemical activity. Surface states are found to be related to the formation of pseudo-brookite clusters by surface Ti segregation. Spectro-ptychography is used for the first time at Ti L3 absorption edge to isolate Ti chemical coordination arising from pseudo-brookite clusters contribution. Correlated with electron microscopy investigation and Density Functional Theory (DFT) calculations, the synchrotron spectromicroscopy data prove unambiguously the origin of the better photoelectrochemical activity of N2- annealed Ti-doped hematite nanorods. Finally, we present here a handy and cheap surface engineering method, beyond the known oxygen vacancy doping, allowing a net gain in the photoelectrochemical activity for the hematite-based photoanodes