posted on 2024-03-18, 13:07authored byMeng Liu, Jifang Zhang, Kaiwei Liu, Zhiwei Nie, Kejing Hu, Jiaming Zhang, Yecheng Tang, Boyang Zhang, Nan Yang, Guijun Ma
The built-in potential in the space charge layer dominates
migration
of charge carriers in a traditional photoelectrode model. In this
work, through particle engineering and surface reconstruction, a Rh-doped
rutile TiO2 (Rh-TiO2) photoelectrode is fabricated,
in which the Rh concentration is decreased gradiently in TiO2 particle directed from conductive substrate to solution. Since the
Rh dopants involve intragap states above the valence band of TiO2, it shapes a built-in potential that orients the migration
of photoexcited holes toward substrate and repels the electrons to
solution side, which change the Rh-TiO2 electrode from
photoanode to photocathode. Comparison of intensity modulated photocurrent
spectroscopy (IMPS) results using ultraviolet and visible light across
a wide potential window unveils the different roles of dopants in
charge dynamics. The operando chemical status of Rh is further verified
by spectroelectrochemical characterization. The present strategy of
directional doping not only is conducive to improving electron–hole
separation but also provides a new approach to unleash the potential
of a semiconductor as both photoanode and photocathode.