Thermal Decomposition of Ternary Sodium Graphite Intercalation Compounds

Abstract

Graphite intercalationc ompounds (GICs) are often used to produce exfoliated or functionalised graphene related materials (GRMs) in as pecific solvent. Thiss tudy explores the formation of the Na-tetrahydrofuran (THF)-GIC and a new ternary system based on dimethylacetamide (DMAc). Detailed comparisons of in situ temperature dependent XRD with TGA-MS and Ramanm easurements reveal as eries of dynamic transformationsd uring heating.S urprisingly,t he bulk of the intercalation compound is stable under ambient conditions, trappedb etween the graphene sheets. Theh eat-ing process drives ar eorganisation of the solventa nd Na molecules, then an evaporation of the solvent;h owever,t he solventl ossi sa rrested by restacking of the graphene layers, leadingt ot rapped solventb ubbles. Eventually,t he bubbles rupture, releasing the remainings olventa nd creating expandedg raphite. These trapped dopants may provideu seful property enhancements, but also potentially confound measurements of grafting efficiency in liquid-phase covalent functionalization experiments on 2D materials.[a] Dr. Figure 4. SEM images of Na-THF-NFG after heating under nitrogen to a,b) 300 8C, and c,d) 650 8C. Am uch greater expansion can be seen at the higher temperature, consistent with XRD. Figure 5. a) XRD patterns of Na-DMAc-NFG at 25 8C, then from 100-700 8Cin2 08Cintervals, and b) magnified diffractograms between 25-280 8C; Co Ka1 1.789 .S tage 1s tructure corresponds to an interlayers pacingo f7 .1 ;t he starred peak is attributed to the "random stage" phaseo rt urbostratic graphite; c) XRD peak intensity of graphite (002), S1B(001) and randomstage structure againstt emperature, with TGA (under N 2 )s hown for comparison.

Sodium Storage Mechanism Investigations through Structural Changes in Hard Carbons

“…The ECD results show that the expansion of the electrode is greater in the sloping region than in the plateau region. This supports the concept that the sloping region is due to ion insertion between graphitic layers since sodium intercalation in graphite typically results in large interlayer expansion . Conversely, pore filling results in a minimal thickness change and therefore supports the assignment of this process occurring during the plateau region, where less pronounced electrode expansion is observed.…”

Effect of graphene flake size on functionalisation: quantifying reaction extent and imaging locus with single Pt atom tags

“…The appearance of kinetically-trapped graphite intercalation compounds (GICs), which are more likely to remain in larger graphite flakes, complicates the interpretation. 14 LFG and its derivatives show very similar diffraction patterns to NFG, with the (003) peak of a stage 1A Na-THF-GIC (2 θ = 23.9°) 14,15 present in the reductively exfoliated samples. For the smaller GP and GNF materials, reductive exfoliation results in a slight weakening of the graphite (002) peak.…”

“…The two-step thermal degradation of the Na-THF intercalants may indicate the presence of two distinct solvent environments, or a partial decomposition of THF followed by further degradation of the remaining fragments. 14 GP showed a continuous solvent loss in the range between 200 °C and 600 °C, with a more pronounced solvent peak at around 520 °C, possibly due to the formation of less defined solvent pockets within the layers. Surprisingly, GNF also showed a two-step mass loss despite its small flake size, most likely due to its graphitic character; although the degradation temperature of the second step was significantly lower (440 °C) than the one observed in the natural graphite sources (∼550 °C).…”

Platinum deposition on functionalised graphene for corrosion resistant oxygen reduction electrodes

“…[1a] FLG was Please do not adjust margins Please do not adjust margins treated with sodium naphthalide in dimethylacetamide (DMAc); DMAc is a good solvent to exfoliate graphite as it can form ternary sodium graphite intercalation compounds (GIC). 21 This reductive exfoliation route achieves a stable dispersion of exfoliated FLG as the charged layers are solvated in the polar solvent. 22 The dark green colour of the sodium naphthalide disappeared after addition to the FLG due to electron transfer from the naphthalide to the graphite feedstock.…”