Emerging two-dimentional (2D) nanomaterials exhibit a wide range of attractive electrical, mechianical, and chemical properties for photonic and electronic applications. In particular, 2D membranes offer unparalleled opportunities and advantages for energy storage applications. To date, 2D electrode materials development for energy applications are still at the stage of trial-and-error. There is a lack of fundamental theories, especially lack of effective characterization tools that would help to guide the design of efficient electrode materials based on 2D materials.<br/>Unlike conventional electrochemistry that measures the electrical current from the entire electrode, the plasmonic-based electrochemical microscope (PECM) technique is based on sensitive imaging of surface plasmonic signal caused by electrochemical reaction, which is measured optically, thus allowing for fast and non-invasive imaging of electrode processes. PECM can image localized chemical reactions on the electrode surface ins-situ, this information will be extremely important for us to understand 2D materials’ charging and discharging process for supercapacitance and ion intercalation process for battery research. The electrochemical reaction will always be accompanied by a conversion of the chemical species between oxidized and reduced states, and plasmonic imaging is extremely sensitive to the species generated (or consumed) on or in the 2D materials. Therefore, the PECM has great potential to characterize the local electrochemical reactions and energy storage process. We have used PECM to map graphene and other 2D materials’ quantum capacitance effect. We have determined both the local density and polarity of charged impurities, and mapped the electron and hole puddles in graphene associated with charged impurities. We further showed that the local quantum capacitance and charge density could be controlled by modifying the supporting substrate with molecules terminated with different charged groups.

Using optical imaging technique to characterize 2D materials for energy research

256th National Meeting (2018)

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