Departmental Seminar

Scanning Electrochemical Microscopy of Graphene-based Hybrids: Insights into Physicochemical Interfacial Processes and Electroactive Site Distribution

Date & time

Mon 31 Jul 2017, 11am–12pm

Location

Room:

Seminar Room (3.17)

Audience

Members of RSPE welcome

Contact

(02)61250363
Dr Sanju Gupta
Department of Physics and Astronomy and Advanced Materials Institute, Western Kentucky University

Surface (and interfacial) chemistry is found in various environments of scientific significance including biomembranes, ocean and atmospheric chemistry and applied electrochemistry. Molecular redox behavior on the surface and at the interface is drastically different than their bulk counterpart. Scanning electrochemical microscopy (SECM) is a powerful tool to investigate interfaces determining ion transfer kinetic rate, diffusion coefficient, imaging topography and electrochemical activity/reactivity. The significant advantages offered by SECM is its capability of probing chemical information of interfacial electron and ion transfer processes at solid/liquid interface irrespective of substrates. A constant potential is applied to the tip and electrochemical working electrode (i.e. the substrate in electrolyte) to drive reaction in bulk electrolyte solution of redox species (or mediator) to probe the surface of certain thickness of graphene-based hybrids. The microscale cyclic voltammograms, probe approach (current versus tip–substrate distance) curves, 2D and 3D micrographs in feedback mode, were chosen for various graphene/transition metal oxide as pseudocapacitors, to probe ion adsorption, electron transfer and map highly electroactive (‘hot spots’) sites. The SECM setup has a resolution of ~100 nm and can locate and relocate areas of interest precisely after a coarse large-area image. We present our findings from viewpoint of reinforcing the roles played by heterogeneous electrode surfaces comprised of graphene nanosheets (conducting)/nanomaterials (semiconducting) via higher/lower probe current distributions. The probe approach curves as well as two- and three-dimensional scans elucidated the existence of regions of different conductivity and the data is analyzed in terms of diffusion coefficient, first-order heterogeneous rate constant, edge plane and electroactive sites density within the probes regions.  

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