Ma Jiwei, Li Wei, Le Nikolay T, Díaz-Real Jesús A, Body Monique, Legein Christophe, Światowska Jolanta, Demortière Arnaud, Borkiewicz Olaf J, Konstantinova Elizaveta A, Kokorin Alexander I, Alonso-Vante Nicolas, Laberty-Robert Christel, Dambournet Damien
Institute of New Energy for Vehicles, School of Materials Science and Engineering, Tongji University, Shanghai 201804, China.
Sorbonne Université, CNRS, Physico-chimie des Électrolytes et Nano-systèmes Interfaciaux, PHENIX, F-75005 Paris, France.
ACS Omega. 2019 Jun 24;4(6):10929-10938. doi: 10.1021/acsomega.9b01219. eCollection 2019 Jun 30.
Manipulating the atomic structure of semiconductors is a fine way to tune their properties. The rationalization of their modified properties is, however, particularly challenging as defects locally disrupt the long-range structural ordering, and a deeper effort is required to fully describe their structure. In this work, we investigated the photoelectrochemical properties of an anatase-type structure featuring a high content of titanium vacancies stabilized by dual-oxide substitution by fluoride and hydroxide anions. Such atomic modification induces a slight red-shift band gap energy of 0.08 eV as compared to pure TiO, which was assigned to changes in titanium-anion ionocovalent bonding. Under illumination, electron paramagnetic resonance spectroscopy revealed the formation of Ti and O radicals which were not detected in defect-free TiO. Consequently, the modified anatase shows higher ability to oxidize water with lower electron-hole recombination rate. To further increase the photoelectrochemical properties, we subsequently modified the compound by a surface functionalization with -methyl-2-pyrrolidone (NMP). This treatment further modifies the chemical composition, which results in a red shift of the band gap energy to 3.03 eV. Moreover, the interaction of the NMP electron-donating molecules with the surface induces an absorption band in the visible region with an estimated band gap energy of 2.25-2.50 eV. Under illumination, the resulting core-shell structure produces a high concentration of reduced Ti and O , suggesting an effective charge carrier separation which is confirmed by high photoelectrochemical properties. This work provides new opportunities to better understand the structural features that affect the photogenerated charge carriers.
操纵半导体的原子结构是调整其性能的一种很好的方法。然而，合理化其改性性能尤其具有挑战性，因为缺陷会局部破坏长程结构有序性，需要更深入的研究来全面描述其结构。在这项工作中，我们研究了一种锐钛矿型结构的光电化学性质，该结构具有通过氟化物和氢氧化物阴离子的双氧化物取代稳定的高含量钛空位。与纯TiO相比，这种原子修饰导致带隙能量轻微红移0.08 eV，这归因于钛 - 阴离子离子共价键的变化。在光照下，电子顺磁共振光谱揭示了Ti和O自由基的形成，而在无缺陷的TiO中未检测到这些自由基。因此，改性锐钛矿表现出更高的氧化水能力，且电子 - 空穴复合率更低。为了进一步提高光电化学性能，我们随后用N - 甲基 - 2 - 吡咯烷酮（NMP）对该化合物进行表面功能化改性。这种处理进一步改变了化学成分，导致带隙能量红移至3.03 eV。此外，NMP供电子分子与表面的相互作用在可见光区域诱导出一个吸收带，估计带隙能量为2.25 - 2.50 eV。在光照下，所得的核壳结构产生高浓度的还原Ti和O，表明有效的电荷载流子分离，这通过高光电化学性能得到证实。这项工作为更好地理解影响光生电荷载流子的结构特征提供了新的机会。
