Scientists have discovered the low-energy {110} surface electrochemical sensing of nanotin dioxide single crystals

Figures (a), (b) and (c) are scanning electron microscopy images of three different morphology of SnO2 exposed at different crystal faces; d) and e) are the crystals of SnO2 electrochemical response to Pb(II) and Cd(II), respectively. Surface effect comparison diagrams; f) and g) are transition diagrams of Pb(II) on the SnO2 {110} and {221} planes; h) and i) are normalized Pb adsorptions respectively An EXAFS pattern of LIII-EXAFS on the crystal surface of SnO2 and the corresponding fitted Fourier transform.

Tin dioxide (SnO2) is a typical wide bandgap (3.6eV) n-type semiconductor material. Due to surface oxygen defects and quantum size effects, it is widely used in gas sensors. However, so far, the electrochemically sensitive properties of different crystals of nano-SnO2 on heavy metal ions have rarely been reported. Recently, Huang Xingjiu, a researcher at the Institute of Intelligent Machinery of the Chinese Academy of Sciences' Institute of Materials Science, discovered the electrochemically sensitive behavior of nano-SnO2 low-energy {110} in the face of heavy metal ions such as Pb(II) and Cd(II), and revealed its response. mechanism. Related results have been published in the Journal of the American Chemical Society (Anal. Chem. 2017, 89, 2613−2621).

Researchers designed and prepared three different morphology of SnO2 nanostructured materials for electrochemical analysis of heavy metal ions in water. The results show that the order of sensitivity of heavy metal ions such as Pb(II) and Cd(II) in different crystal planes of SnO2 nanostructured materials is: low-energy {110} plane> high-energy {221} plane. Adsorption and desorption experiments revealed that the desorption capacity of Pb(II) and Cd(II) on the different crystal planes of SnO2 nanostructured materials is consistent with the order of electrochemical response, although Pb(II) and Cd(II) have low energy in SnO2 nanostructured materials. The adsorption amount on the {110} plane is much smaller than that on the high-energy {221} plane, however, it easily desorbs to the electrode surface on the low-energy {110} plane, and thus excellent electrochemical performance can be obtained on the low-energy {110} plane. At the same time, the researchers collaborated with Li Qunxiang, a professor at the China National University of Science and Technology's Microscale National Laboratory, to use DFT simulation experiments. Theoretical calculations show that Pb(II) has a diffusion energy of 0.63 eV on the low energy {110} plane of SnO2 nanostructured materials. It is much smaller than the 1.88eV adsorption energy on the high-energy {221} crystal plane. In addition, using the Shanghai Synchrotron Radiation Facility (BL14W1 station), the researchers used XAFS spectroscopy to analyze the structural parameters of Pb(II) on the low-energy {110} and high-energy {221} planes of SnO2 nanostructure materials. The results of the study indicate that the The bond length of the Pb-O bond of Pb(II) on the low energy {110} plane is larger than the high energy {221} plane. The combination of DFT calculation and XAFS spectroscopic analysis explains the electrochemical response mechanism of Pb(II) and Cd(II) on the atomic level for different exposed SnO2 nanostructured materials.

This work reveals the mechanism of the influence of the crystal surface on the electrochemical behavior at the atomic level, and it is of great significance for the deep understanding of the relationship between the electrochemical behavior and the crystal plane, and for designing an electrochemical sensor interface from the source to improve its performance. Theoretical guidance and practical application value.

The research work was supported by the Innovation Crossing Team of the Chinese Academy of Sciences, the National Natural Science Foundation, and the Shanghai Synchrotron Radiation Facility (BL14W1 Line Station).