nanocrystals*

One of the best studied photocatalysts is TiO₂. As chemical reactions occur on surfaces, the surface of TiO₂ has been extensively investigated [1]. However, focus has largely been on 2D surfaces of bulk crystals, while real catalysts are nanocrystals or nanoparticles. Surface reconstruction on a nanocrystal is expected to be different with multiple facets. Here, we report on reconstructed surfaces on rutile nanocrystals studied by environmental transmission electron microscopy [2]. The reconstruction is imaged using an electron direct detection detector (DDD). The DDD provides significantly improved signal/noise ratio and high spatial resolution. Using these new approaches [3], we observed the surfaces of {110}, {210}, and {100} on TiO₂ nanocrystals at atomic resolution and compared with previous models and with DFT calculations of atomic positions and total energies. Most importantly, the results allow an examination of surface reconstruction dependence on nanocrystal sizes.
[1] U. Diebold, Surface Science Reports 48 (5-8), 53 (2003).
[2] W. Gao et al., Scientific Reports 7 (1), 17243 (2017).
[3] A. Yoon and J-M. Zuo, Microscopy and Microanalysis 25 (S2), 1680 (2019).