High efficient charges separation-type photo-electrode with controlled energy band-bending

半导体同质结和异质结引起的能带弯曲是通过光电极裂解水实现高效制氢的关键因素。本研究以粉末、单晶和薄膜三种形式制备了施主掺杂的钛酸锶(Sr(Ti&lt；1x&gt；Nb_x)O&lt；3+5&gt；3+5&gt；1x&gt；Nb_x)与二氧化钛的复合材料，研究了染料的光漂白、分水光反应、染料敏化光电流和离子吸附等各种化学现象。(1)用Sr(Ti_&lt；1-x&gt；Nb_x)O_&lt；3+δ&gt；/TiO_2复合粉末敏化的亚甲基蓝溶液的光漂白速度比单独用TiO_2敏化的快几倍。该粉末对亚甲基蓝有很强的吸附作用。这揭示了结点附近光激电荷的空间分离。(2)当采用Sr(Ti_&lt；0.98&gt；Nb_&lt；0.02&gt；)O_&lt；3+δ&gt；单晶片作为光电极时，其光电流是玻璃片的1.5倍或2倍。采用溶胶-凝胶法制备了二氧化钛薄膜。在单光照射下，Sr(Ti_&lt；0.98&gt；Nb_&lt；0.02&gt；)O_&lt；3+δ&gt；单晶/TiO_2的开启波长向20 nm(0.1 eV)方向移动。(3)这证明了异质结中尖峰的存在，从而证实了异质结引起的带弯曲现象。(4)研究了钛基合金板上锶(Ti&lt；i-x&gt；Nb_5)O&lt；3+5&gt；/TiO_2结的制备及复合粉末对离子吸附的控制。(5)控制吸附在电极上的离子物种必须成为光电化学反应的重要内容。上述研究结果可应用于高效光电化学水分离。

An energy band-bending induced by homo-and hetero-junctions of semiconductors must be a key factor for attainment of efficient hydrogen production via photo-electrode water splitting. In the present study, composites of TiO_2 with donor-doped titanate, Sr(Ti_<1x>Nb_x)O_<3+5> in states of powder, single crystal and thin film, were prepared, and various pysico-chemical phenomena, i.e., photo-bleaching of dyes, water splitting photo-reaction, dye-sensitized photo-current, and ions adsorption, were investigated. (1) Photobleaching of methylene blue aqueous solution sensitized with Sr(Ti_<1-x>Nb_x)O_<3+δ>/ TiO_2 composite powders proceeded several time faster than that with TiO_2 alone. Strong adsorption of MB on the powder was observed. This revealed spatial separation of photo-excited charges near the junction. (2) When Sr(Ti_<0.98>Nb_<0.02>)O_<3+δ> single crystal plate covered by TiO_2 thin film was used as a photo-electrode, the photo-current was larger 1.5 or 2 times than that for glass plate with FTO thin film covered by TiO_2 thin film. The TiO_2 thin film was prepared by sol-gel method. (When mono-light was irradiated, on-set wavelength for Sr(Ti_<0.98>Nb_<0.02>)O_<3+δ> single crystal / TiO_2 was shifted toward shorter wavelength 20 nm (0.1 eV) than that for FTO glass plate / TiO_2. (3)This proved the existence of spike in the heterojunction, end therefore this confirms the appearance of band-bending due to heterjunction. (4)The preparation of Sr(Ti_<i-x>Nb_5)O_<3+5>/ TiO_2 junction on the Ti-based alloy plates and controlling of ion adsorption on the composite powder were examined. (5) The controlling of the ion species adsorbed on the electrode must become important for photo-electrochemical reaction. The findings described above should be applied for highly efficient photo-electrochemical water splitting