Scanning probe microscopy（SPM）
By employing in-situ scanning probe microscopy (STM and AFM), our research group carries out investigations mainly on the structure and reaction kinetics of electrochemical interfaces in concentrated electrolytes, charge transport through atomic sized metal contact and single molecules and electrochemical control, surfaces and interfacial structures and processes of energy electrochemistry systems, including the formation and properties of solid-electrolyte interphase (SEI), Li deposition and dissolution, and grain boundary effect of perovskite solar cell under working conditions. Meanwhile, we also develop electrochemical methods for applications in detection and control.
We undertake or participate in a number of key projects of NSFC and subprojects of national basic research programs of China, and carry out national and international collaborative researches. In the past five years, the research group has published more than 30 peer-reviewed papers in journals including Nature Comm., Chem, J. Am. Chem. Soc., Angew. Chem. Int. Ed, Adv. Mat., Chem. Commun., Electrochimica Acta, ChemElectroChem. Current main research directions are scanning probe microscopy, ionic liquid electrochemistry and energy electrochemistry.
For a long time, we have been making efforts to develop methods of scanning probe microscopy (STM and AFM) for applications in electrochemical interface and interdisciplinary researches. Atomic scale resolution electrochemical in-situ STM (EC-STM) is employed to follow the structure and process of electrochemical interfaces; STM break junction (STM-BJ) technique is developed to form single molecular junctions with asymmetric electrode; using AFM long-range and property probing capability, the electric double layer (EDL) structures in ionic liquids are studied and nanomechanical properties of SEIs are studied. AFM single molecule force spectrum has also been applied to study the inter- and intra-molecular interactions of biomolecules.
EC-STM is used to study the adsorption, reconstruction and electrodeposition processes of single crystal electrode surfaces. Structural details of the EDL of ionic liquid electrochemical interfaces are studied to expand the understanding of the electrochemical interface structure and properties of concentrated electrolytes. Equivalent electric circuit is constructed based on the EDL structure to establish the relationship between the microscopic structure and the macroscopic characteristics of EDL. Furthermore, charge transfer kinetics of redox molecules at well-defined single crystal electrode-ionic liquid interfaces and its correlation with EDL structure are studied.
In recent years, our research interest has expanded to the fundamental investigations on the surface and interfacial processes of electrochemical energy systems: combined with in-situ SPM and Raman spectroscopy, surface and interface processes and properties of dye sensitized and perovskite solar cells have been studied successively. Very recenty, concepts and methods of surface electrochemistry have been applied to study the process of lithium electrode and to design surface lithiophilicity of substrate for lithium anodes. Nanomechanical properties of solid electrolyte boundary film (SEI) on lithium negative electrode are studied by AFM force curve technique along with electrochemical performance so that a method for evaluating the SEI and its electrochemical performance is established.
Based on STM-BJ technique, we develop method to construct metal atomic-sized contacts and single-molecule junctions, and use electrochemistry and magnetic field as the stimuli to regulate the charge transport through heterojunctions. Room temperature ionic liquids are employed so that metal atomic contacts of transition metals and magnetic metals can be constructed; STM-BJ is further developed by making use of electrochemical assisted “jump to contact” mechanism to construct single molecular junctions with asymmetric electrodes. Attentions are paid to the correlation between redox molecular conductance and electrochemical charge transfer rate, as well as mutual interaction between redox reaction at and quantum transport of gold atomic contact. Finally, magnetic field is introduced into STM-BJ platform, which allows to construct a controllable single molecule spintronic junctions; meanwhile tunneling anisotropic magnetoresistance (TAMR) effect of single molecules is demonstrated.
We develop chip-based complex microelectrodes and utilize electrochemical bipolar principle to improve the detection capability of electroactive species; To study the electrical and mechanical properties of nano-BLMs, we apply biomimic membranes on glass nanopores and nanopores on silicon nitride for combined investigations by electrochemical impedance spectroscopy (EIS) and AFM; Based on bipolar electrochemical principle of hydrogen permeable Pd thin foil, an electrochemically driven large-scale periodical pH alteration method is developed, and its application for acid-base driven DNA denaturation and renaturation is demonstrated.