A. Li Bassi

C. Casari

C. Castiglioni

F. Ciccacci

G. Bussetti

L. Brambilla

L. Duo'

M. Passoni

M. Tommasini

P. Biagioni

R. Yivlialin

English

Archivio istituzionale della ricerca - Politecnico di Milano

Disclosing the early stages of electrochemical anions intercalation in graphite by AFM and STM investigationsR. Yivlialin1*, G. Bussetti1, A. Li Bassi2, C. Casari2, M. Passoni2, C. Castiglioni3, M. Tommasini3, L. Brambilla3, P. Biagioni1, F. Ciccacci1and L. Duò11 Dept. of Physics, Politecnico di Milano, p.za Leonardo da Vinci 32,  20133, Milano, Italy, 2 Dept. of Energy, Politecnico di Milano, v. Ponzio 34/3 20133, Milano, Italy3Dept. of Chemistry, Materials and Chemical Engineering, Politecnico di Milano, p.za Leonardo da Vinci 32, 20133, Milano, Italy.* Presenting Author: rossella.yivlialin@polimi.it abstractWide-size graphene sheets with single- or few-layer thickness and low defectivity are crucial for the future development of graphene-based applications. Different strategies can be used for graphite delamination and graphene production: mechanical, chemical and electrochemical; the chemical/electrochemical strategies ensuring large amounts of graphene and a good quality of the products. So far, optimization of the procedural protocols was generally undertaken through a systematic investigation of the delaminated graphene flakes, while less attention has been paid to the processed graphite crystal. The current state of research in this field requires a better comprehension of the molecular mechanisms involved during the intercalation of ions within the crystal, which represents the first step towards the crystal swelling and the subsequent exfoliation of graphite. This investigation can be tackled at the nanoscale by a combination of scanning probe microscopies (with atomic resolution) with specific chemical monitoring techniques. A choice is offered by the so-called electrochemical atomic force and scanning tunnelling microscopies (EC-AFM and EC-STM, respectively). However, EC-STM has been rarely if not at all exploited for a nanoscale investigation of the first intercalation stages so far, despite the inherent improvement in spatial resolution that it offers compared to EC-AFM. This fact is probably due to the intrinsic difficulty in piloting the STM tip during the intercalation of ions.  	In this work, we monitor the surface changes of graphite as a function of the electrochemical potential by both EC-AFM and EC-STM coupled with cyclic voltammetry. Following this strategy, we reveal the surface modifications encountered for different electrolytes during the early intercalation stages: surface faceting, step erosion, terrace damages, and nano-protrusions, all affecting the graphite surface and therefore the exfoliation process. The in situ analysis of the surface modification is combined with ex situ Raman analysis, aimed at the detection of chemical and/or structural modification of the graphite samples subjected to different EC treatment. In particular spectroscopic markers related to ions intercalation and/or doping and to the formation of defected areas/edges are identified and analyzed. We believe that, within the current debate on the delamination of layered crystals, our findings represent a significant step towards a better understanding of the intercalation process in graphite. 

Disclosing the early stages of electrochemical anions intercalation in graphite by AFM and STM investigations

https://re.public.polimi.it/bitstream/11311/1239061/1/abstract_NanoSea.docx

Disclosing the early stages of electrochemical anions intercalation in graphite by AFM and STM investigations

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Archivio istituzionale della ricerca - Politecnico di Milano