Available on-demand - F.MT01.01.04
Graphene—A Promising Electrode Material in Liquid Cell Electrochemistry
Shu Fen Tan1,Kate Reidy1,Serin Lee1,Julian Klein1,Nicholas Schneider2,Haeyeon Lee1,Frances Ross1
Massachusetts Institute of Technology1,Renata Global2
Two-dimensional (2D) materials such as graphene and transition metal dichalcogenides (TMDs) are potential candidate materials for electrodes due to their exceptional intrinsic properties including their high specific surface area, high electrical charge mobility and good thermal conductivity and mechanical strength. Graphene in particular shows tuneable structures and electrocatalytic activity, excellent conductivity, good chemical resistance and mechanical flexibility, as well as the ease and low cost of production. Graphene-based composites have been explored as next generation electrode materials for electrical and optical devices, supercapacitors, organic electronics and dye-sensitized solar cells and graphene itself is considered a promising electrode material for applications ranging from photocatalysis and solar cell to optoelectronic devices. In electron microscopy, graphene is used in a different way: its remarkable mechanical and scavenging properties make it ideal for graphene liquid cells1 where liquid is encapsulated between two graphene sheets for high-resolution imaging. However, the transfer method of graphene to fabricate high quality graphene liquid cells and the reproducibility of making liquid pockets with sufficient volume, exact chemical content and well-defined thickness are key experimental challenges with graphene liquid cells. Recent studies circumvent leakage issues by using a liquid cell that is a hybrid of SiNx and graphene to form leak-proof liquid confinement.2 Furthermore, separating top and bottom graphene windows with a thin layer of hexagonal boron nitride (hBN) enables more control over liquid thickness and can provide a two-fold improvement in resolution3 compared to conventional graphene liquid cells. Despite these and other advances in engineering 2D materials into liquid cell design, the full functionality associated with microfabricated liquid cells, such as addition of electrochemical, heating or flowing and mixing capabilities, are generally still absent.
Here we focus on the opportunities arising from the use of 2D materials in liquid cell electrochemistry. To establish whether 2D materials can indeed evolve into a reliable electrode material for both electroanalytical chemistry and electron microscopy, we need to develop a reproducible protocol in transferring 2D materials onto microfabricated liquid cell chips to achieve reliable electrical contact and mechanical robustness. We describe liquid cells equipped with 2D material electrodes and show results aimed at understanding the interplay of kinetics and thermodynamics during electrochemical deposition, measuring parameters such as the shape, size and epitaxy of electrochemically deposited nanoparticles. We discuss the effects of external parameters such as the thickness and nature of the 2D materials and the deposition potential and we consider beam damage of these 2D materials. Exploring the possibility of 2D materials as electrode materials potentially opens up new opportunities for investigating a wide range of problems pertaining to energy storage and electrocatalysis.
1. Yuk, J. M.; Park, J.; Ercius, P.; Kim, K.; Hellebusch, D. J.; Crommie, M. F.; Lee, J. Y.; Zettl, A.; Alivisatos, A. P., High-Resolution EM of Colloidal Nanocrystal Growth Using Graphene Liquid Cells. Science 2012, 336 (6077), 61-64.
2. Rasool, H.; Dunn, G.; Fathalizadeh, A.; Zettl, A., Graphene-sealed Si/SiN cavities for high-resolution in situ electron microscopy of nano-confined solutions (Phys. Status Solidi B 12/2016). physica status solidi (b) 2016, 253 (12), 2544-2544.
3. Kelly, D. J.; Zhou, M.; Clark, N.; Hamer, M. J.; Lewis, E. A.; Rakowski, A. M.; Haigh, S. J.; Gorbachev, R. V., Nanometer Resolution Elemental Mapping in Graphene-Based TEM Liquid Cells. Nano Letters 2018, 18 (2), 1168-1174.