In situ direct observation of photocorrosion in ZnO crystals in ionic liquid using a laser-equipped high-voltage electron microscope

Abstract

ZnO photocatalysts in water react with environmental water molecules and corrode under illumination. ZnO nanorods in water can also grow because of water splitting induced by UV irradiation. To investigate their morphological behavior caused by crystal growth and corrosion, here we developed a new laser-equipped high-voltage electron microscope and observed crystal ZnO nanorods immersed in ionic liquid. Exposing the specimen holder to a laser with a wavelength of 325 nm, we observed the photocorrosion in situ at the atomic scale for the first time. This experiment revealed that Zn and O atoms near the interface between the ZnO nanorods and the ionic liquid tended to dissolve into the liquid. The polarity and facet of the nanorods were strongly related to photocorrosion and crystal growth.

Photochemistry and the role of light during the submerged photosynthesis of zinc oxide nanorods

“…The SAED pattern (Fig. 4d ) was obtained along the direction, and the growth direction is along the c -axis, with a O-terminated polar surface, which is in accordance with previous reports 30 , 37 . The ratios of O and Zn were obtained from their electron diffraction spectroscopy (EDS) profile, and the results are shown in the inset table in Fig.…”

“…The generated electrons build up at the apical portion of the nanobumps to generate a cathodic environment, whereas the holes left at the bottom of the concave nanobumps create a local anode 21 , 39 . Photochemical water-splitting reactions (reaction (2)) then build up holes at the bottom, which subsequently contribute to OH radical generation and to the photocorrosion of ZnO (reaction (3)) 37 , 40 . …”

Highly reduced ecotoxicity of ZnO-based micro/nanostructures on aquatic biota: Influence of architecture, chemical composition, fixation, and photocatalytic efficiency

“…In addition, the photocatalyst shape and architecture also affects the photocorrosion effect, since nanoparticles and micro/nanoferns, which have larger surface area and a greater ability to trap light, present a lower photocorrosion than ZnO films. These results confirm that the photocorrosion activity is strongly related to crystal morphology (i.e., different facets) and the physical properties of the ZnO surface, having more photo-stability ZnO micro/nanomaterials with a (002) preferred orientation (Debroye, et al, 2017;Ishioka, et al, 2017). In contrast, ZnO@ZnS(4h) core@shell architectures exhibited excellent anti-photocorrosive properties, with a ZnO dissolution of less than 5%, due to the effective transfer of photogenerated holes from the ZnO core to the ZnS shell, both protecting the surface oxygen of ZnO from the solution and preventing the attack of the surface oxygen atom by the holes transported to the catalyst/solution interface (Torabi, et al, 2015, Yu, et al, 2015.…”

Photocatalytic Hydrogen Production from Glycerol Aqueous Solution Using Cu-Doped ZnO under Visible Light Irradiation

“…Cu-doped ZnO-based photocatalysts, prepared by a precipitation method, were studied in For all the reuse cycles, photocatalytic hydrogen production was substantially unchanged, being in the range of 4750-4775 µmol/L. These results evidenced the stability of the Cu-doped ZnO sample in photocatalytic hydrogen production from a glycerol aqueous solution under visible light and that no photocorrosion phenomena (typical of ZnO-based photocatalysts [62][63][64]) occurred in the used operating conditions.…”