New progress has been made in the study of FeOOH crystal structure and crystal dependent electrochemical analysis behavior

Recently, Yang Meng, a postdoctoral fellow of Huang Xingjiu research group, Institute of intelligent machinery, Hefei Research Institute, Chinese Academy of Sciences, cooperated with Lin Chuhong, an associate researcher, to study the cross-section structure of FeOOH nanorods with different crystal phases and clarify the crystal growth direction by using the rotation mode of transmission electron microscope (TEM); combined with the fine structure of synchrotron radiation X-ray absorption (XAFS ）The new mechanism of dominant crystal phase in the process of heavy metal ion electrochemical analysis was revealed by means of technology and kinetic simulation The relevant research results have been accepted and published by small magazine of Wiley press (DOI: 10.1002/small.201906830) Metal hydroxide nanomaterials are widely used in the field of energy and environment due to their excellent catalytic properties Although it has been reported that different crystal structures of metal hydroxide nanomaterials show unique electrochemical properties, due to the complex catalytic reaction system, there are many factors affecting their electrocatalytic properties, so it is difficult to confirm the key factors behind the crystal phase dependent electrochemical behavior of metal hydroxide nanomaterials On the one hand, there is a lack of understanding of the interaction between nanomaterials and target analytes at the atomic level; on the other hand, the kinetic process of catalytic reaction is not very clear In addition, there is no direct evidence for the internal structure and growth direction of different crystal phases of metal hydroxide nanomaterials It is important to clarify the relationship between the structure and electrochemical properties of nanomaterials for the design of effective sensitive interfaces Fig 1 TEM Study on the cross section structure and crystal growth direction of α - and β - FeOOH nanorods (source: small) Based on the above problems, the researchers first synthesized rod-shaped α - and β - FeOOH, and studied the cross section shape by rotating different angles of transmission electron microscope, combined with the analysis results of crystal surface corresponding to lattice fringe spacing and nano diffraction, The cross section of α - FeOOH nanorods is rhombus, while that of β - FeOOH nanorods is square, and the growth direction of α - and β - FeOOH nanorods is [001] Then, the sensitive interface of α - and β - FeOOH nanorods was used to study the electrochemical analysis behavior The detection results show that the sensitivity of α - FeOOH to Pb (II) is about 17 times higher than that of β - FeOOH The enhancement mechanism of the detection signal of α - FeOOH nanorods, the dominant phase in electrochemical analysis, was elucidated by means of XAFS technique and dynamic simulation The results of XAFS and FT-IR show that more surface hydroxyl groups are found on α - FeOOH than on β - FeOOH, which is helpful for the enrichment of target analyte Pb (II), while the longer pb-o bond adsorbed on α - FeOOH promotes the diffusion of Pb (II) to the electrode surface for redox reaction, thus obtaining enhanced electrochemical signal The simulation results of the kinetic process show that the adsorption rate and capacity of α - and β - FeOOH to the target analyte are the decisive factors for the enhancement of electrochemical sensitivity of the dominant phase Figure 2 Synchrotron radiation XAFS technology, kinetic simulation calculation, infrared spectrum and other research on the crystal structure, bonding mode, bond length, adsorption kinetic process and the electrochemical behavior mechanism (source: small) dependent on FeOOH crystal phase The understanding of the structure provides the experimental basis for the surface atomic arrangement model; on the other hand, it reveals the new mechanism of sensitivity enhancement of the electrochemical analysis behavior of the dominant crystalline phase from the atomic level, which provides an effective theoretical support for the study of new nano materials for electrochemical analysis and detection and the functional application of other metal hydroxide nano materials The research work has been supported by the key projects of NSFC, Boxin program, and the later projects of Chinese doctors.