Phase-Transition Mechanism and the Atomic Interface Structure of Brookite to Rutile: Resolving from Machine-Learning Global Pathway Sampling

• Published in: Journal of physical chemistry. C 2022-07, Vol.126 (28), p.11846-11854
• Main Authors: Chen, Zi-Yan, Chen, Gu-wen, Zhu, Sheng-Cai
• Format: Article
• Language: English
• Subjects: C: Physical Properties of Materials and Interfaces
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.2c03301

The rich structural polymorphism of TiO2 provides an opportunity to construct a heterophase junction, which reportedly improves the photocatalyst performance. In the past, using the partial phase transition to fabricate brookite/rutile biphase materials has attracted much attention. Although many of the experiments have studied the phase transition of brookite to rutile, to date, the atomistic mechanisms and its atomic heterophase junction structure remain unclear. In this paper, the stochastic surface walking method and neural network method (SSW-NN) are utilized to map out the local potential energy surface (PES) of brookite and resolve the lowest energy barrier transition path. We show that brookite first transforms into the TiO2-II structure, and then the TiO2-II transforms into rutile with the overall orientation relation (100)B//(100)II, [010]B//[010]II, and (001)II//(101)R, [100]II//[010]R. Anatase is a byproduct rather than an intermediate phase during the brookite-to-rutile phase transition. The well-matched interfaces between brookite and TiO2-II, TiO2-II, and rutile possess spatially separated CBM and VBM, while the disordered junction between brookite and rutile shows frustrated electron/hole transport. The proposed mechanisms not only clarify the role of anatase in the brookite-to-rutile transition but also help to understand the nature of higher photocatalyst performance of the biphase.