Nishikawa Masami, Shiroishi Wataru, Honghao Hou, Suizu Hiroshi, Nagai Hideyuki, Saito Nobuo
Department of Materials Science and Technology, Nagaoka University of Technology , 1603-1 Kamitomioka, Nagaoka 940-2188, Japan.
Process Technology Center, Mitsui Chemicals Inc. , 580-32 Nagaura, Sodegaura 299-0265, Japan.
J Phys Chem A. 2017 Aug 17;121(32):5991-5997. doi: 10.1021/acs.jpca.7b05214. Epub 2017 Aug 3.
For an Ir-doped TiO (Ir:TiO) photocatalyst, we examined the most dominant electron-transfer path for the visible-light-driven photocatalytic performance. The Ir:TiO photocatalyst showed a much higher photocatalytic activity under visible-light irradiation than nondoped TiO after grafting with the cocatalyst of Fe. For the Ir:TiO photocatalyst, the two-step photoexcitation of an electron from the valence band to the conduction band through the Ir doping level occurred upon visible-light irradiation, as observed by electron spin resonance spectroscopy. The two-step photoexcitation through the doping level was found to be a more stable process with a lower recombination rate of hole-electron pairs than the two-step photoexcitation process through an oxygen vacancy. Once electrons are photoexcited to the conduction band by the two-step excitation, the electrons can easily transfer to the surface because the conduction band is a continuous electron path, whereas the electrons photoexcited at only the doping level could not easily transfer to the surface because of the discontinuity of this path. The observed two-step photoexcitation from the valence band to the conduction band through the doping level significantly contributes to the enhancement of the photocatalytic performance.
对于铱掺杂的二氧化钛（Ir:TiO）光催化剂，我们研究了其可见光驱动光催化性能中最主要的电子转移路径。在用铁作为助催化剂接枝后，Ir:TiO光催化剂在可见光照射下表现出比未掺杂的二氧化钛更高的光催化活性。对于Ir:TiO光催化剂，通过电子自旋共振光谱观察到，在可见光照射下，电子从价带通过铱掺杂能级两步光激发到导带。发现通过掺杂能级的两步光激发是一个更稳定的过程，与通过氧空位的两步光激发过程相比，其空穴-电子对的复合率更低。一旦电子通过两步激发被光激发到导带，由于导带是连续的电子路径，可以很容易地转移到表面，而仅在掺杂能级被光激发的电子由于该路径的不连续性则不容易转移到表面。观察到的从价带通过掺杂能级到导带的两步光激发显著有助于光催化性能的提高。
