Chi Qianqian, Zhu Genping, Jia Dongmei, Ye Wei, Wang Yikang, Wang Jun, Tao Ting, Xu Fuchun, Jia Gan, Li Wenhao, Gao Peng
College of Material, Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou, Zhejiang 311121, P. R. China.
Nanoscale. 2021 Mar 4;13(8):4496-4504. doi: 10.1039/d0nr08928a.
Photocatalytic overall water splitting to simultaneously obtain abundant hydrogen and oxygen is still the mountain that stands in the way for the practical applications of hydrogen energy, in which composite semiconductor photocatalysts are critical for providing both electrons and holes to promote the following redox reaction. However, the interface between different components forms a deplete layer to hinder the charge transfer to a large extent. In order to enhance the charger transfer from an interface to the surface and promote the spatial separation of electron-hole pairs, a built-in electric field induced by a p-n heterojunction emerges as the best choice. As a touchstone, a p-n heterojunction of TiO2/BiOBr with a strong built-in electric field has been constructed, which presents a wide spectrum response owing to its interleaved band gaps after composition. The built-in electric field greatly enhances the separation and transportation of photogenerated carriers, resulting in fluorescence quenching due to the carrier recombination. The sample also displayed exceptional photoelectron responses: its photocurrent density (43.3 μA cm-2) was over 10 times that of TiO2 (3.5 μA cm-2) or BiOBr (4.2 μA cm-2). In addition, the sample with a molar ratio of 3 : 1 between TiO2 and BiOBr showed the best photocatalytic overall water splitting performance under visible light (λ > 420 nm): the hydrogen and oxygen production rate were 472.7 μmol gcat.-1 h-1 and 95.7 μmol gcat.-1 h-1, respectively, which are the highest values under visible light without other cocatalysts to have been reported in literature for the photocatalyst.
光催化全水分解以同时获得大量氢气和氧气仍然是氢能实际应用的拦路虎，其中复合半导体光催化剂对于提供电子和空穴以促进后续的氧化还原反应至关重要。然而，不同组分之间的界面形成耗尽层，在很大程度上阻碍了电荷转移。为了增强电荷从界面到表面的转移并促进电子 - 空穴对的空间分离，由p - n异质结诱导的内建电场成为最佳选择。作为试金石，构建了具有强内建电场的TiO₂/BiOBr p - n异质结，由于其复合后的交错带隙，呈现出宽光谱响应。内建电场极大地增强了光生载流子的分离和传输，由于载流子复合导致荧光猝灭。该样品还表现出优异的光电子响应：其光电流密度（43.3 μA cm⁻²）是TiO₂（3.5 μA cm⁻²）或BiOBr（4.2 μA cm⁻²）的10倍以上。此外，TiO₂与BiOBr摩尔比为3∶1的样品在可见光（λ > 420 nm）下表现出最佳的光催化全水分解性能：产氢和产氧速率分别为472.7 μmol gcat⁻¹ h⁻¹和95.7 μmol gcat⁻¹ h⁻¹，这是在没有其他助催化剂的可见光条件下，该光催化剂在文献中报道的最高值。
