Carbonaceous Materials Investigated by Small-Angle X-ray and Neutron Scattering

Abstract

Carbonaceous nanomaterials have become important materials with widespread applications in battery systems and supercapacitors. The application of these materials requires precise knowledge of their nanostructure. In particular, the porosity of the materials together with the shape of the pores and the total internal surface must be known accurately. Small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) present the methods of choice for this purpose. Here we review our recent investigations using SAXS and SANS. We first describe the theoretical basis of the analysis of carbonaceous material by small-angle scattering. The evaluation of the small-angle data relies on the powerful concept of the chord length distribution (CLD) which we explain in detail. As an example of such an evaluation, we use recent analysis by SAXS of carbide-derived carbons. Moreover, we present our SAXS analysis on commercially produced activated carbons (ACN, RP-20) and provide a comparison with small-angle neutron scattering data. This comparison demonstrates the wealth of additional information that would not be obtained by the application of either method alone. SANS allows us to change the contrast, and we summarize the main results using different contrast matching agents. The pores of the carbon nanomaterials can be filled gradually by deuterated p-xylene, which leads to a precise analysis of the pore size distribution. The X-ray scattering length density of carbon can be matched by the scattering length density of sulfur, which allows us to see the gradual filling of the nanopores by sulfur in a melt-impregnation procedure. This process is important for the application of carbonaceous materials as cathodes in lithium/sulfur batteries. All studies summarized in this review underscore the great power and precision with which carbon nanomaterials can be analyzed by SAXS and SANS.

Deactivation and Regeneration of Zeolite Catalysts Used in Pyrolysis of Plastic Wastes—A Process and Analytical Review

“…Du et al used SAXS to precisely characterize microporous zeolites, revealing consistent structural and surface information on the molecular scale [190]. On top of that, in a recent review, Härk et al emphasized the great efficiency of SAXS for analyzing carbonaceous materials [191]. Saurel et al successfully applied this technique to ordered and disordered carbonaceous materials and obtained a full description of the pore and atomic structure of the studied compounds [192].…”

Anomalous Self‐Optimizing Microporous Graphene‐Based Lithium‐ion Battery Anode from Laser Activation of Small Organic Molecules

“…[ 47 ] As shown in Figure 2i, Figure 6i, and Figure 6k, an obvious peak at q of 0.0947 Å can be observed on the SAXS profiles of both fresh and cycled N‐LIG samples, which corresponds to the ordering of microporous structure in graphene. [ 48 ] After subtracting the baseline, it is obvious that the peak position gradually shifts to the low‐ q region from 3.1 @ 400 @ N to 3.5 @ 400 @ N and from 3.1 @ 800 @ N to 3.5 @ 800 @ N, as shown in Figure 6j and Figure 6l. For quantitative analysis, the fitting on the peak was conducted (Figure S37, Supporting Information) and parameters including q of peak and FWHM were extracted and recorded in Table S3 (Supporting Information).…”

Interconnected Microporous and Mesoporous Carbon Derived from Pitch for Lithium–Sulfur Batteries

“…Furthermore, the intensity of the SANS data in the high q region is associated with the scattering length density contrast between the carbon walls and the encapsulated material in the pores. 38 The intensity of SANS of XU76 carbon in the high q region decreases after the sulfur encapsulation process, mainly due to the lower scattering length density contrast of sulfur (Figure 2f). 38 On the other hand, there is little change in scattering intensity at high q after sulfur loading for KB carbon (Figure 2e).…”

“…38 The intensity of SANS of XU76 carbon in the high q region decreases after the sulfur encapsulation process, mainly due to the lower scattering length density contrast of sulfur (Figure 2f). 38 On the other hand, there is little change in scattering intensity at high q after sulfur loading for KB carbon (Figure 2e). Thus, a lower amount of sulfur was infiltrated into the micropores (subnanometer) of KB carbon.…”

“…33 Compared to small-angle X-ray scattering (SAXS), 34−36 the stronger contrast between carbon and sulfur in the SANS technique allows us to see whether the sulfur accesses the micro/nanopores of the carbon materials used. 33,37,38 Thus, we used SANS to study the porous nature of carbon materials and to probe the distribution of sulfur in the pore network after sulfur encapsulation and the d-THF infiltration process. Figure 2e,f shows the SANS results of KB and XU76 carbon before and after sulfur encapsulation and d-THF infiltration.…”